Low-temperature heat capacity of the pseudo-one-dimensional magnetic systems CsMnCl3.2H2O, -RbMnCl3.2H2O, and CsMnBr3.2H2O

The heat capacity of the isomorphic pseudo-one-dimensional magnetic systems CsMnCl3.2H2O, -RbMnCl3.2H2O, and CsMnBr3.2H2O has been analyzed using recently developed estimates for the lattice heat capacity of anisotropic media. The magnetic contribution in the paramagnetic region could be described very well by the S=52 linear-chain Heisenberg model. The intrachain interaction is found as Jk=-3.0 K for the former two compounds and Jk=-2.6 K for the latter compound. The interchain interactions are smaller by two orders of magnitude. The results, are compared with other experimental evidence. A study of the critical behavior of the magnetic entropy increase yields ==+0.100.01 for all three substances.</p

Low-temperature heat capacity of the pseudo-one-dimensional magnetic systems CsMnCl3.2H2O, -RbMnCl3.2H2O, and CsMnBr3.2H2O

The heat capacity of the isomorphic pseudo-one-dimensional magnetic systems CsMnCl3.2H2O, -RbMnCl3.2H2O, and CsMnBr3.2H2O has been analyzed using recently developed estimates for the lattice heat capacity of anisotropic media. The magnetic contribution in the paramagnetic region could be described very well by the S=52 linear-chain Heisenberg model. The intrachain interaction is found as Jk=-3.0 K for the former two compounds and Jk=-2.6 K for the latter compound. The interchain interactions are smaller by two orders of magnitude. The results, are compared with other experimental evidence. A study of the critical behavior of the magnetic entropy increase yields ==+0.100.01 for all three substances.</p

Specific heat of nearly-one-dimensional tetramethyl ammonium manganese trichloride (TMMC) and tetramethyl ammonium cadmium trichloride (TMCC)

The specific heat of tetramethyl ammonium manganese trichloride and its cadmium isomorph is measured for 2&lt;T&lt;52 K. The temperature dependence of the lattice specific heat of the cadmium compound could be fitted with an expression based upon a pseudoelastic approach of the lattice vibrations in this low-dimensional system. Application of this approach to the manganese compound yields a magnetic contribution which fits the overall behavior of a one-dimensional Heisenberg model with an intrachain interaction of Jk=-6.70.5 K. Inspection of the low-temperature region yields a satisfactory agreement with the expression Cm=1.1|kTJ|+0.5|kTJ|2-0.13|kTJ|3, predicted by recent calculations.</p

Specific heat of nearly-one-dimensional tetramethyl ammonium manganese trichloride (TMMC) and tetramethyl ammonium cadmium trichloride (TMCC)

The specific heat of tetramethyl ammonium manganese trichloride and its cadmium isomorph is measured for 2&lt;T&lt;52 K. The temperature dependence of the lattice specific heat of the cadmium compound could be fitted with an expression based upon a pseudoelastic approach of the lattice vibrations in this low-dimensional system. Application of this approach to the manganese compound yields a magnetic contribution which fits the overall behavior of a one-dimensional Heisenberg model with an intrachain interaction of Jk=-6.70.5 K. Inspection of the low-temperature region yields a satisfactory agreement with the expression Cm=1.1|kTJ|+0.5|kTJ|2-0.13|kTJ|3, predicted by recent calculations.</p

Water and salt transport in plaster/substrate systems

The transport of salt and water during drying has been studied in systems consisting of a substrate covered with either one or two plaster layers. The drying behaviour of these systems was modelled with invasion percolation (IP) algorithms. The model outcomes were compared with experimental results obtained with Nuclear Magnetic Resonance (NMR). It was found that drying behaviour of the plaster layers was strongly influenced by the properties of the substrate. When the substrate has the widest pores, the plaster layers stay wet while the substrate dries out. As a consequence most salt, present in the substrate, moves to the plaster layers and accumulates at the external surface. In the case that the substrate has the smallest pores, the plaster layers dry out first. In this case salts also crystallize in the substrate. Further we have tried to make an accumulating plaster system consisting of two layers on top of a substrate, which would function purely on the basis of differences in pore sizes between the layers. The drying behaviour in the presence of pure water was as predicted by the model. However, in the case of a salt solution the salt modified the drying behaviour such that the accumulation properties of the system were reduced. Therefore, we conclude that for transporting systems tuning the pore-sizes of the layers suffices, but for accumulating systems it seems that additives , for example water repellents, have to be used

Quasi-one-dimensional behavior of (CH3)2NH2MnCl3 (DMMC)

The heat capacity of dimethyl ammonium manganese trichloride has been investigated for 1.6&lt;T&lt;50 K. A transition to a three-dimensional antiferromagnetically ordered state has been observed at 3.60 K, which is supported by nuclear-magnetic-resonance and susceptibility measurements. The critical entropy did amount to 3.4%. The magnetic heat capacity in the paramagnetic region could be described very well by a S=52 Heisenberg linear chain system with Jk=-5.8±0.7 K. The data for kT|J|&lt;1.5, together with the earlier data on (CH3)4NMnCl3, corroborate the suggested low-temperature behavior of such a system.</p

A digital device for measuring high-order structure functions

We describe a prototype digital device for measuring high-order structure functions in turbulence. Because the structure function is a special case of the correlation function, the device may find usage outside the study of turbulence. The device operates at 20 kHz on 12-bits data and updates probability distribution functions of signal differences for 64 arbitrarily chosen time delays in real time