Cuprates intermediate between one and two dimensions

The key elements in all known cuprate superconductors are lightly doped CuO_i-planes. Recently a new homologous series of compounds Sr_n–1Cu_n+1O_2n have been reported in which the planes contain a parallel array of line defects which form a trellis lattice with ladder-segments of the square lattice weakly coupled through triangular line defects. The width of the ladder segments is determined by the parameter n and varies from single chains to arbitrarily wide ladders. The magnetic properties of undoped compounds will be dominated by the properties of the ladders. Heisenberg s = 1/2 ladders can have a spin liquid groundstate with a spin gap if the number of rungs is odd so that a short range RVB groundstate is predicted for such trellis lattices. Using a t-J model to describe the doped material leads to the prediction of a d-wave RVB superconducting groundstate with a large spin gap.     

Epidural hematoma with atypical clinical course

The prognosis of epidural haematomas (EDH) is generally favourable if an operation is carried out in good time. Suspected EDH is mostly diagnosed as a result of a "typical" neurological manifestation (initial unconsciousness/asymptomatic interval/loss of consciousness), which then leads to an in-depth diagnosis (X-ray of the skull, CT, MRI). However, atypical clinical manifestations are frequent and can result in dangerous delays in diagnosis and treatment. A decisive factor in the early detection of EDH is close clinical-neurological monitoring by specially trained staff and their prompt reaction when changes occur, no matter how minor. Qualitative changes in the patient's state of consciousness and behaviour are just as important in this respect as quantitative ones.     

Impurity effect on Kramer-Pesch core shrinkage ins-wave vortex and chiralp-wave vortex

The low-temperature shrinking of the vortex core (Kramer-Pesch effect) is studied for an isolated single vortex for chiral p-wave and s-wave superconducting phases. The effect of nonmagnetic impurities on the vortex core radius is numerically investigated in the Born limit by means of a quasiclassical approach. It is shown that in the chiral p-wave phase the Kramer-Pesch effect displays a certain robustness against impurities owing to a specific quantum effect, while the s-wave phase reacts more sensitively to impurity scattering. This suggests chiral p-wave superconductors as promising candidates for the experimental observation of the Kramer-Pesch effect.     

Large strain rate-dependent response of elastomers at different strain rates: convolution integral vs. internal variable formulations

Two different viscoelastic frameworks adapted to large strain rate-dependent response of elastomers are compared; for each approach, a simple model is derived. Within the Finite Linear Viscoelasticity theory, a time convolution integral model based on an extension to solid of the K-BKZ model is proposed. Considering the multiplicative split of the deformation gradient into elastic and inelastic parts, an internal variable model based on a large strain version of the Standard Linear Solid model is considered. In both cases, the strain energy functions involved are chosen neo-Hookean, and then each model possesses three material parameters: two stiffnesses and a viscosity parameter. These parameters are set to ensure the equivalence of the model responses for uniaxial large strain quasi-static and infinitely fast loading conditions, and for uniaxial rate-dependent small strain loading conditions. Considering their responses for different Eulerian strain rates, their differences are investigated with respect to the strain rate; more specifically, both stiffness and dissipative properties are studied. The comparison reveals that these two models differ significantly for intermediate strain rates, and a closing discussion highlights some issues about their foundations and numerical considerations.     

WO3 nano-ribbons: their phase transformation from tungstite (WO3·H2O) to tungsten oxide (WO3)

Tungsten oxide (WO₃) nano-ribbons (NRs) were obtained by annealing tungstite (WO₃·H₂O) NRs. The latter was synthesized below room temperature using a simple, environmentally benign, and low cost aging treatment of precursors made by adding hydrochloric acid to diluted sodium tungstate solutions (Na₂WO₄·2H₂O). WO₃ generates significant interests and is being used in a growing variety of applications. It is therefore important to identify suitable methods of production and better understand its properties. The phase transformation was observed to be initiated between 200 and 300 ^°C, and the crystallographic structure of the NRs changed from orthorhombic WO₃·H₂O to monoclinic WO₃. It was rigorously studied by annealing a series of samples ex situ in ambient air up to 800 ^°C and characterizing them afterward. A temperature-dependent Raman spectroscopy study was performed on tungstite NRs between minus 180 and 700 ^°C. Also, in situ heating experiments in the transmission electron microscope allowed for the direct observation of the phase transformation. Powder X-ray diffraction, electron diffraction, electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy were employed to characterize precisely this transformation.     

Modelling diffusion and adsorption of As species in Fe/GAC adsorbent beds

BACKGROUND: Arsenic decontamination of drinking water by adsorption is a simple and robust operation. When designing packed bed adsorbers for arsenic, the main problems are the slow diffusion kinetics of As in microporous media and the lack of simple equations for predicting the performance of the equipment. Commercial iron‐doped granular activated carbon adsorbents (Fe/GAC) for groundwater arsenic abatement were studied in this work. Basic parameters for arsenate (As^V) adsorption were measured and their performance at larger scale was simulated with an approximate analytical model. RESULTS: In the 0–300 µg_As L^?1 range, the As^V adsorption isotherm on Fe/GAC was found to be approximately linear. Assuming Henry's law for adsorption and homogeneous surface diffusion with constant diffusivity for intrapellet mass transfer, an approximate model for flow and adsorption of arsenate inside packed bed adsorbers was developed, and reduced to an analytic compact solution using the quasi‐lognormal distribution (Q‐LND) approximation. The use of this model with fitted and reported parameters enabled the approximate simulation of industrial adsorbers and home point‐of‐use filters. Results show that industrial adsorbers meet the breakthrough condition with incomplete utilization of the adsorbent unless convenient process configurations are used. In point‐of‐use systems with short residence times intraparticle diffusion would drastically reduce the adsorbent performance. CONCLUSION: Assuming linear adsorption of As^V over Fe/GAC, an analytical approximate solution for flow and adsorption in packed beds can be obtained. The model seems to represent correctly the main features of industrial and home filters, however, more experimental data is necessary for scale‐up purposes. Copyright © 2011 Society of Chemical Industry     

The Specific Heat and the Fermi Surface Anisotropy in Sr2RuO4

The influence of the Fermi surface anisotropy on the specific heat jump is studied for the p-wave superconductor with a gap function d = z^(k _x ± ik _y ) in connection with Sr₂RuO₄. It is shown that the normalized specific heat jump, C/T _c , is reduced from its universal value, 1.43, in accordance with experimental findings. We show that this behavior fits well into our present understanding of the quasiparticle spectrum and the impurity effects.