Modeling of Deformable Cell Separation in a Microchannel with Sequenced Pillars

Embedded pillar microstructures are an efficient approach for controlling and sculpting shear flow in a microchannel but have not yet demonstrated to be effective for deformability-based cell separation and sorting. Although simple pillar configurations (lattice, line sequence) worked well for size-based separation of rigid particles, they had a low separation efficiency for circulating cells. The objective of this study was to optimize sequenced microstructures for separation of deformable cells. This was achieved by numerical analysis of pairwise cell migration in a microchannel with multiple pillars, which size, longitudinal spacing, and lateral location as well as the cell elasticity and size varied. This study revealed two basic pillar configurations optimized for deformability-based separation: 1) “duplet” that consists of two closely spaced pillars positioned far below the centerline and above the centerline halfway to the wall; and 2) “triplet” composed of three widely-spaced pillars located below, above and at the centerline, respectively. The duplet configuration is well suited for deformable cell separation in short channels, while the triplet or a combination of duplets and triplets provides even better separation in long channels. These optimized pillar microstructures can dramatically improve microfluidic methods for sorting and isolation of blood and rare circulating tumor cells.

A quantitative evaluation of different regions of skin in adult Iranian native sheep

The present investigation aimed to evaluate the histomorphometric features of the skin of the Iranian native sheep (Bakhtiari breed). A total of 24 apparently healthy Iranian Bakhtiari sheep, aged 1–2 years were analysed and categorised on the basis of sex (12 females and 12 males). Samples were taken as small pieces from different regions of the skin, fixed and stained with H&E. The quantitative evaluations of different regions of skin were carried out using lattice line graticule (5 × 5) and light microscopy. The Student t-test and one-way ANOVA were used to analyse the data and detect significant differences. Results showed that the volume densities of different histological structures varied between sexes and among the different regions. No significant difference was observed in volume densities of sebaceous glands, arrector pili muscles and blood vessels, but the other parameters studied differed significantly among the regions. Except for the arrector pili muscle and connective tissue, the volume densities of other tissue structures were significantly affected by sex.  

The blue coloration in banded fluorite (Blue John) from Castleton, Derbyshire, England

SummaryFrom the microscopic examination of lightly etched, cleaved (111) surfaces of banded blue fluorite (Blue John, from Castleton, Derbyshire) it is concluded that the coloured lamellae are not necessarily or exclusively associated with lattice-line imperfections. Elemental analyses, by electron dispersive methods, of fresh cleavage (111) surfaces in the immediate vicinity of small inclusions (c. 10 µm diameter) possessing associated coloured haloes detected no appreciable concentrations of impurities. From the evidence available, it is suggested that the zones of blue colour consist of colloidal calcium resulting from radiation damage caused by the intermittent deposition of radioactive material on the surfaces of fluorite during crystal development. The dispersion of colloidal calcium produced is particularly stable as a consequence of the close correspondence between lattice spacings in calcium fluoride and in calcium metal.

The Spin Lattice Relaxation of the Nuclear Dipolar Energy in Some Organic Crystals with Slow Molecular Motions

The relaxation of nuclear dipolar energy to the lattice has been measured in three different organic solids (benzene, cyclohexane and hexamethylbenzene) as a function of temperature. In the cases of C6H8 and C6(CH3)6 very slow motions associated with rather high activation energy were detected near the melting point. They are thought to be thermally activated rotations of the molecules about axes other than the hexad axis. In the case of cyclohexane the activation energy for the process of molecular diffusion was determined directly from the experimental results without the need of a model for vacancy diffusion. A maximum in dipolar relaxation rate was always observed for correlation times of the order of the rigid lattice line width i. e. in the temperature region where the lines narrow.