In this paper we demonstrate high spatial resolution hydrodynamic flow profiling in silicon wafer based microchannels using single molecule fluorescence correlation spectroscopy (FCS). We have used confocal fluorescence microscopy to detect single tetramethylrhodamine (TMR-4-dUTP) biomolecules traversing a approximately 1 fL volume element defined by an argon laser beam focus. By elevating a (approximately 10(-10) M) reservoir of diluted analyte, a continuous hydrodynamic flow through the microstructure could be accomplished. The microchannel was then scanned with a diffraction-limited focus in approximately 1-microm steps in both the vertical and the horizontal directions to determine the flow profile across a 50 x 50 microm2 channel. The flow profile measured was parabolic in both dimensions, thereby showing a Poiseuille laminar flow profile. Future microstructures can hereby be nondestructively investigated with the use of high spatial resolution confocal correlation microscopy.

Purpose The goal was to study the effects of early cervical headgear treatment on maxillary and mandibular dental arch area, shape and interarch dimensions. Methods The total study group comprised 67 children aged 7.6 years (standard deviation 0.3) with Angle class II malocclusion collected between 1992 and 1996. The children were randomly divided into two groups of equal size. In the first group, cervical headgear treatment was started immediately and undertaken for 2 years. The remaining patients served as untreated controls. Dental casts were taken and scanned at the beginning of treatment (T0) and at the 2‑year (T1) and 4‑year follow-up (T2). Three-dimensional landmarks describing the positions of maxillary and mandibular incisors, canines, first and second premolars and first molars were used to calculate and visualize the maxillary and mandibular dental arch area and shape using the polynomial equation y = Ax6 + Bx2. Results Significant changes in the shape and area of both maxillary and mandibular dental arches were induced with cervical headgear. The headgear increased dental arch area, sagittal dimensions at the mid-sagittal line and transversal dimensions at all of the measured levels in both dental arches compared to the control group. Conclusions Cervical headgear is an effective treatment device to gain space in both dental arches. Furthermore, when used as an early phase treatment, relapse is relatively small compared to the gained space.

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