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Broszura wydana w ramach projektu Uniwersytet Młodych Wynalazców "Stymulujemy geo- i bioróżnorodność. Projektowanie sieci zadrzewień w krajobrazie rolniczym, czyli informatyka dla przyrodnika", finansowanego przez Ministerstwo Nauki i Szkolnictwa Wyższego.

We report low-temperature specific heat, $C(T)$, measurements on (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ with $x=0.01$ and $x=0.03$, where nonmagnetic Lu atoms are randomly distributed on antiferromagnetic $S=1/2$ Heisenberg chains with $J/k_{\mathrm B}=28$ K. The observed reduction of $C$ below 15 K with increasing $x$ is accurately described by quantum transfer matrix simulations without any adjustable parameter, implying that the system is an excellent experimental realization of segmented quantum spin chains. Finite-size effects consistent with conformal-field theory predictions are leading to the formation of an effective low-energy gap. The size of the gap increases with Lu content and accounts for the impurity driven reduction of the specific heat. For both concentrations our results verify experimentally the low temperature scaling behavior established theoretically and also confirm the value of $J$ determined from pure Yb$_4$As$_3$., Comment: 7 pages, 6 figures

Willin/FRMD6 was first identified in the rat sciatic nerve, which is composed of neurons, Schwann cells, and fibroblasts. Willin is an upstream component of the Hippo signaling pathway, which results in the inactivation of the transcriptional co-activator YAP through Ser127 phosphorylation. This in turn suppresses the expression of genes involved in cell growth, proliferation and cancer development ensuring the control of organ size, cell contact inhibition and apoptosis. Here we show that in the mammalian sciatic nerve, Willin is predominantly expressed in fibroblasts and that Willin expression activates the Hippo signaling cascade and induces YAP translocation from the nucleus to the cytoplasm. In addition within these cells, although it inhibits cellular proliferation, Willin expression induces a quicker directional migration towards scratch closure and an increased expression of factors linked to nerve regeneration. These results show that Willin modulates sciatic nerve fibroblast activity indicating that Willin may have a potential role in the regeneration of the peripheral nervous system.