Annular and circular rigid inclusions planted into a penny-shaped crack and factorization of triangular matrices.

Analytical solutions to two axisymmetric problems of a penny-shaped crack when an annulus-shaped (model 1) or a disc-shaped (model 2) rigid inclusion of arbitrary profile are embedded into the crack are derived. The problems are governed by integral equations with the Weber-Sonine kernel on two segments. By the Mellin convolution theorem, the integral equations associated with models 1 and 2 reduce to vector Riemann-Hilbert problems with 3 × 3 and 2 × 2 triangular matrix coefficients whose entries consist of meromorphic and plus or minus infinite indices exponential functions.

Nonlinear bending models for beams and plates.

A new nonlinear model for large deflections of a beam is proposed. It comprises the Euler-Bernoulli boundary value problem for the deflection and a nonlinear integral condition. When bending does not alter the beam length, this condition guarantees that the deflected beam has the original length and fixes the horizontal displacement of the free end.

The tetrapeptide AcSDKP, a negative regulator of cell cycle entry, inhibits the proliferation of human and chicken lymphocytes.

The tetrapeptide AcSer-Asp-Lys-Pro (AcSDKP) is a physiological negative regulator of hematopoiesis in mammals. It acts by blocking the cell cycle entry of quiescent stem cells and progenitors. In the present study we report that AcSDKP blocks the proliferation of human as well as chicken lymphocytes.