Magnetic anomalies in the spin chain system, Sr3_3Cu1−x_{1-x}Znx_xIrO6_6

We report the results of ac and dc magnetization (M) and heat-capacity (C) measurements on the solid solution, Sr$_3$Cu$_{1-x}$Zn$_x$IrO$_6$. While the Zn end member is known to form in a rhombohedral pseudo one-dimensional K$_4$CdCl$_6$ structure with an antiferromagnetic ordering temperature of (T$_N$ =) 19 K, the Cu end member has been reported to form in a monoclinically distorted form with a Curie temperature of (T$_C$ =) 19 K. The magnetism of the Zn compound is found to be robust to synthetic conditions and is broadly consistent with the behavior known in the literature. However, we find a lower magnetic ordering temperature (T$_o$) for our Cu compound (~ 13 K), thereby suggesting that T$_o$ is sensitive to synthetic conditions. The Cu sample appears to be in a spin-glass-like state at low temperatures, judged by a frequency dependence of ac magnetic susceptibility and a broadening of the C anomaly at the onset of magnetic ordering, in sharp contrast to earlier proposals. Small applications of magnetic field, however, drive this system to ferromagnetism as inferred from the M data. Small substitutions for Cu/Zn (x = 0.75 or 0.25) significantly depress magnetic ordering; in other words, T$_o$ varies non-monotonically with x (T$_o$ ~ 6, 3 and 4 K for x = 0.25, 0.5, and 0.67 respectively). The plot of inverse susceptibility versus temperature is non-linear in the paramagnetic state as if correlations within (or among) the magnetic chains continuously vary with temperature. The results establishComment: 7 pages, 7 figures, Revte

In vitro heart valve tissue engineering

Heart valve replacement represents the most common surgical therapy for end-stage valvular heart diseases. A major drawback all contemporary heart valve replacements have in common is the lack of growth, repair, and remodeling capabilities. To overcome these limitations, the emerging field of tissue engineering is focusing on the in vitro generation of functional, living heart valve replacements. The basic approach uses starter matrices of either decellularized xenogeneic or biopolymeric materials configured in the shape of the heart valve and subsequent cell seeding. Moreover, in vitro strategies using mechanical loading in bioreactor systems have been developed to improve tissue maturation. This chapter gives a short overview of the current concepts and provides detailed methods for in vitro heart valve tissue engineering