Universal Micro Research Articles

Study of Drag Forces on a Designed Surface in Bubbly Water Lubrication Using Electrolysis

To study the drag reduction effect of a bubbly fluid, a pin-disk experiment is performed on the Universal Micro Tribotester system. Bubbles are generated by water electrolysis in holes that are specially designed on the disk surface. Experiment result shows that the drag force experiences a dynamic process, both drag reduction and drag increment effects appear in the process depending on the bubble behavior. This process is numerically simulated using computational fluid dynamics (CFD), and the explanations for the drag variation are given based on the analysis of drag forces on each wall of the disk surface. The drag reduction occurs when the bubble fills the hole, as the viscous drag on the air-liquid surface is small, and the pressure drag is reduced as the side wall of the hole is covered by the bubble. The drag increment is thought to be caused by the increment of the fluid viscosity when the bubble leaves the hole and flows in the fluid.

Changes in the Nuclear Structure During Thyroid Carcinogenesis in Rats. An Image Analysis Study

The nuclear and chromatin structure of normal, hyperplastic, and neoplastic thyroid epithelial cells was studied using new methods for preparing semi-thin sections and for image analysis. Data acquisition for computorized image processing was performed by means of a scanning universal micro spectrophotometer. Thyroid cell proliferation and tumor growth were induced in Wistar rats after treatment of the animals with methylthiouracil (MTU) for different time periods. During the stage of diffuse and nodular hyperplasia, an increase in nuclear surface area and decrease in nuclear DNA content and DNA concentration was observed. The surface area and circumference ratio of the nucleus in various thyroid tumors were similar to those of the controls. However, DNA content and concentration in the follicular carcinomas were smaller than those of the controls and of papillary carcinomas. In MTU treated animals (during the stage of diffuse and nodular hyperplasia and during frank tumor growth), a tendency toward reduction in the number of centrally located chromocenters was observed. Their surface area increased significantly only during nodular hyperplasia. However, no difference was found in the number, surface, area, and circumference ratio of chromocenters among follicular, papillary, and trabecular carcinomas of the thyroid gland. DNA concentration in chromocenters was lower during nodular hyperplasia and in follicular carcinomas than that of the controls or papillary carcinomas. The changes in the total (centrally plus peripherally located chromocenters) condensed chromatin were in general similar to those of the cenrally-located chromocenters alone. During nodular hyperplasia and in follicular carcinomas, the surface area and the circumference of all chromocenters were higher than those of the controls. DNA concentration exhibited a decrease during nodular hyperplasia and in follicular carcinomas, and an increase in papillary carcinomas. The difference in DNA content between follicular and papillary carcinomas is thought to be due to a higher proliferation capacity in papillary carcinomas or perhaps to a difference in staining reactivity. Die Kern- und Chromatinstruktur normaler, hyperplastischer und neoplastischer Schilddrüsenzellen wurde mit einem neuen, durch Kombination von Cytophotometrie und Datenverarbeitung erarbeiteten Verfahren der Analyse mikroskopischer Bilder untersucht. Durch Verfütterung von Methylthiouracil (MTU) wurde bei Ratten eine Proliferation derSchilddrüse bzw. eine Induktion von Tumoren ausgelöst. Während der diffusen und nodulären Hyperplasie konnte eine Vergröβerung des Kernes und eine Abnahme der DNS-Konzentration beobachtet werden. In den untersuchten Schilddrüsentumoren waren dagegen die Gröβe und die Gestalt der Kerne ähnlich wie in den unbehandelten Kontrollen. Die DNS-Konzentration war in follikulären Carzinomen geringer als in papillären. Die Zahl der im Inneren des Kernes gelegenen Chromozentren zeigt unter MTU eine leichte Tendenz zur Abnahme. In den verschiedenen Tumorformen (follikuläre, papilläre und trabekuläre) unterschieden sich die Chromozentren weder in der Zahl noch der Gröβe, noch in der äuβeren Gestalt. Bei der nodulären Hyperplasie steigt die Gröβe der Chromozentren dagegen an. Gleichzeitig fällt die DNS-Konzentration ab. Sie ist ebenfalls gering in den follikulären Carcinomen, während die papillären Carcinome ähnliche Konzentration wie die Kontrollen aufwiesen. Betrachtet man zusätzlich das an der Kernwand gelegene kompakte Chromatin, so findet man ähnliche Verhältnisse wie bei den zentralen Chromozentren allein. Bei der nodulären Hyperplasie und den follikulären Carcinomen werden die Chromozentren gröβer und stärker gelappt, die in ihnen zu findende DNS-Konzentration wird kleiner im Gegensatz zu den papillären Carcinomen, wo sie gegenüber den Kontrollen ansteigt. Dieser Unterschied zwischen den beiden Tumorformen reflektiert möglicherweise die höhere Proliferationskapazität der papillären Carcinome, unter Umständen auch eine unterschiedliche Reaktivität gegenüber der Färbereaktion.

A universal micro heating stage

There is described an electrically-heated, circular aluminum block which serves as stand and heating stage for many types of microchemical glass and porcelain ware. It is readily adaptable to automatic temperature control and is generally applicable in micro and semi-micro preparations and analyses.