Influence of flexoelectric effect on the Fréedericksz transition in chiral nematic liquid crystals.

Electric field driven Frèedericksz transition in chiral nematic (cholesteric) planar liquid crystal cell is studied in the presence of flexoelectric effect. An inhomogeneity of electric field and finiteness of anchoring energy are considered. The extra contribution to the electric field induced by flexoelectricity is taken into account as well as the common contribution arising from the applied voltage U.

First-order and continuous Fréedericksz transitions in cholesteric liquid crystals.

The Fréedericksz transition in twist cells of cholesteric liquid crystals with a finite surface energy is considered. It is shown that this transition can be either of the second order or of the first order depending on the values of the Frank constants, pitch, surface energies, and the cell thickness. A simple criterion that determines the order of the phase transition is obtained.

[Morphological and immunohistogenetical features of colon cancer in children].

We carried out postmortem and immunohistological studies of 3 cases of colon cancer in a 14-year-old (case 1) and an 8-year-old girl (case 2), and Turcot's syndrome in a 14-year-old girl (case 3). Tumors were located in the proximal portions of the colon and they were of rare histological types. The expression of proteins--the products of MLH 1, MHS2, and MHS6 genes responsible for DNA reparation was estimated.

Fossilized embryos are widespread but the record is temporally and taxonomically biased.

We report new discoveries of embryos and egg capsules from the Lower Cambrian of Siberia, Middle Cambrian of Australia and Lower Ordovician of North America. Together with existing records, embryos have now been recorded from four of the seven continents. However, the new discoveries highlight secular and systematic biases in the fossil record of embryonic stages.