Evidence of quantum criticality in the doped Haldane system Y2BaNiO5

Experimental bulk susceptibility X(T) and magnetization M(H,T) of the S=1-Haldane chain system doped with nonmagnetic impurities, Y2BaNi1-xZnxO5 (x=0.04,0.06,0.08), are analyzed. A numerical calculation for the low-energy spectrum of non-interacting open segments describes very well experimental data above 4 K. Below 4 K, we observe power-law behaviors, X(T)=T^-alpha and M(H,T)/T^(1-alpha)=f(alpha,(H/T)), with alpha (<1) depending on the doping concentration x.This observation suggests the appearance of a gapless quantum phase due to a broad distribution of effective couplings between the dilution-induced moments.Comment: 4 pages, 3 figure

Random interactions and spin-glass thermodynamic transition in the hole-doped Haldane system Y2−x_{2-x}Cax_xBaNiO5_5

Magnetization, DC and AC bulk susceptibility of the $S$=1 Haldane chain system doped with electronic holes, Y$_{2-x}$Ca$_x$BaNiO$_5$ (0$\leq$x$\leq$0.20), have been measured and analyzed. The most striking results are (i) a sub-Curie power law behavior of the linear susceptibility, $\chi (T)$$\sim$ $T$$^{-\alpha}$, for temperature lower than the Haldane gap of the undoped compound (x=0) (ii) the existence of a spin-glass thermodynamic transition at $T$$_g$ = 2-3 K. These findings are consistent with (i) random couplings within the chains between the spin degrees of freedom induced by hole doping, (ii) the existence of ferromagnetic bonds that induce magnetic frustration when interchain interactions come into play at low temperature.Comment: 4 pages, 4 figures, to appear in Phys. Rev.

Thio-photocatalysis II: Synthesis of dioctylsulfide in the liquid phase by the photocatalytic addition of 1-octanethiol on 1-octene

Schoumacker, K. Cattenot, M. Geantet, C. Puzenat, E. Lacroix, M. Herrmann, J. M.Photocatalytic synthesis of dioctylsulfide has been performed at room temperature in liquid phase by addition of 1-octanethiol on 1-octene in contact with illuminated TiO2. Under inert atmosphere, dioctylsulfide is selectively obtained whereas in the presence of oxygen high selectivity in n-dioctylsulfide has vanished. This study illustrates the potential of photocatalysis for the production of thio-compounds. (C) 2010 Elsevier B.V. All rights reserved

BIOTEX – Bio-sensing textiles for healthcare

Chemical analysis of body fluids non-invasively is a novel and exciting area of personalised wearable healthcare systems. BIOTEX was an EU FP6 project that developed wearable textile sensors to collect and analyse sweat in real-time. A textile patch has been designed in such a way that it can successfully collect sweat from human subjects during exercise. The patch uses the inherent capillarity of fabrics to transport sweat through a fabric channel with integrated sensing capability. A super-absorbent ma-terial at the end of the channel is used to draw the fluid through the chan-nel and store waste products. This provides a passive pumping action re-quiring no external power. Sensors integrated into the fabric channel measure sweat pH, sodium concentration and conductivity. In addition physiological measurements including respiration and ECG are measured using piezo-resistive fabric and textile electrodes respectively. A thoracic blood oxygenation sensor has also been developed using a woven fibre optic configuration. A central control unit is used to interface the sensors and transmit data via Bluetooth to a graphical user interface displayed on a nearby laptop for analysis