Twist-bend nematic liquid crystals in high magnetic fields.

We present magneto-optic measurements on two materials that form the recently discovered twist-bend nematic (N_{tb}) phase. This intriguing state of matter represents a fluid phase that is orientationally anisotropic in three directions and also exhibits translational order with periodicity several times larger than the molecular size. N_{tb} materials may also spontaneously form a visible, macroscopic stripe texture. We show that the optical stripe texture can be persistently inhibited by a magnetic field, and a 25T external magnetic field depresses the N-N_{tb} phase transition temperature by almost 1{∘}C. We propose a quantitative mechanism to account for this shift and suggest a Helfrich-Hurault-type mechanism for the optical stripe formation.

Nematic twist-bend phase with nanoscale modulation of molecular orientation.

A state of matter in which molecules show a long-range orientational order and no positional order is called a nematic liquid crystal. The best known and most widely used (for example, in modern displays) is the uniaxial nematic, with the rod-like molecules aligned along a single axis, called the director. When the molecules are chiral, the director twists in space, drawing a right-angle helicoid and remaining perpendicular to the helix axis; the structure is called a chiral nematic. Here using transmission electron and optical microscopy, we experimentally demonstrate a new nematic order, formed by achiral molecules, in which the director follows an oblique helicoid, maintaining a constant oblique angle with the helix axis and experiencing twist and bend. The oblique helicoids have a nanoscale pitch. The new twist-bend nematic represents a structural link between the uniaxial nematic (no tilt) and a chiral nematic (helicoids with right-angle tilt).

[Comparative assessment of the WHO and Gilson histological classifications of prostatic neoplasms (taking into account data of ploidy studies)]. / Sravnitel'naia otsenka gistologicheskikh klassifikatsii zlokachestvennykh opukholei predstatel'noi zhelezy VOZ i Glisona (s uchetom dannykh ploidometricheskogo issledovaniia).

We estimated ploidometric nuclear parameters of predominating cell population in various prostatic adenocarcinomas in using WHO vs Glison classification to define advantages of the above classifications. Ploidometry provides information on cell composition and proliferative activity of cells. We observed greater ploidity in different grades of cell atypia. WHO histological classification by differentiation grade corresponds to ploidometric characterization of tumor cell populations but fails to reflect the presence of different histological types of the tumor. Currently introduced classification by Glison is more effective both diagnostically and prognostically as it reveals a dominant histological type of the tumor and shows other variants of tumor growth progression.