Experimental and Numerical Investigations of Thermal Stratification Effects

In the frame of this work, thermal stratification effects withincooling channel flow of hydrogen cooled combustion chambers are investigated with theoretical approaches. Experimental results with a hydrogen cooled cylindrical combustion chamber segment with four different cooling channel geometries are presented. A new stratification approach that consideres the limited mixing capabilities within the turbulent core flow of the cooling channel is validated with the help of the experimental results

Effect of compression loading on human mesenchymal stem cells-collagen microspheres in an ovine intervertebral disc organ culture: a preliminary study

Posters: P1091The 2010 World Forum for Spine Research (WFSR 2010): The Intervertebral Disc, Montreal, Canada, 5-8 July 2010

Effect of limited nutrition on in situ intervertebral disc cells under simulated-physiological loading

STUDY DESIGN. Whole ovine caudal intervertebral discs (IVD) were cultured in sufficient and limited nutrition under simulated-physiologic loading for 7 and 21 days. OBJECTIVE. To study the effect of limited nutrition on disc cells embedded in their native tissue in short- and midterm whole organ disc culture. SUMMARY OF BACKGROUND DATA. Nutrient-limited induction of disc cell death in vitro has been demonstrated and is believed to be a factor in disc degeneration. Nutrient-limited cell death and its consequences, as it relates to degeneration, have not been investigated in the intact IVD. METHODS. Ovine IVDs with endplates were cultured for 7 and 21 days under simulated-physiologic loading, either in media with limited (2 g/L) or sufficient (4.5 g/L) glucose concentration. Cell viability, relative gene expression, newly synthesized chondroitin sulfate content, and matrix metalloproteinase (MMP) activity were measured after culture and compared to fresh tissue. RESULTS. In sufficient glucose media, cell viability was maintained through 7 days to 21 days of culture. In limited glucose, it dropped significantly to 62% in the anulus fibrosus and to 56% in the nucleus pulposus after 7 days and remained so until 21 days (63% in the anulus fibrosus and 52% in the nucleus pulposus). No significant differences were found between culture conditions for relative gene expression, newly synthesized chondroitin sulfate and inactive and active forms of MMP13 and MMP7. CONCLUSION. With this culture system, whole IVD explants could be maintained up to 21 days. Cell viability decreased to 50% to 60% under limited nutrition within days and remained so up to 3 weeks. The surviving cells did not compensate matrix production in this time frame. © 2009 Lippincott Williams & Wilkins, Inc