RESUMO
Underwater spark-discharge methods have been widely utilized for experimental studies in many fields such as material processing, water treatment, and cavitation bubble dynamics. However, the precise control of bubble size using this method has been difficult. This poses challenges to better understand the complex interactions of non-spherical cavitation bubble growth and collapse, which require fine and careful control of bubble size. A novel low-voltage (60.0 V) underwater spark-discharge method using a metal-oxide-semiconductor field effect transistor is presented here. We are able to repeatedly generate oscillating bubbles of consistent maximum radius, a. The dependency of the total circuit resistance to spark-generated bubble size in this method is discussed.
RESUMO
Using monoclonal antibodies recognizing the shared determinants of the CD45 (T-200) antigen we have been able to distinguish spleen colony-forming units (CFU-s) whose progeny are self-renewing from other colony formers on the basis of their quantitative expression of this antigen(s). We have also been able to identify a population of cells that is capable of producing 12-day colonies but has only a limited capacity to produce 8-day colonies. CFU-s8 are found primarily in the dim T-200 population, whereas CFU-s12 were found in both the bright and dim population, but the cells within the colonies produced by these two populations differ in their capacity for self-renewal as CFU-s. Only the colonies dissected after 12 days from the spleens of mice receiving T-200-bright bone marrow cells contained significant numbers of cells that were capable of forming colonies after retransplantation. We calculate the frequency of these cells in total bone marrow to be approximately 1 in 5000.