Virial coefficients and equations of state for mixtures of hard discs,hard spheres and hard hyperspheres

The composition-independent virial coefficients of a d-dimensional binary mixture of (additive) hard hyperspheres following from a recent proposal for the equation of state of the mixture (Santos, A., Yuste, S. B., and López de Haro, M., 1999, Molec. Phys., 96, 1) are examined. Good agreement between theoretical estimates and available exact or numerical results is found for d = 2, 3, 4 and 5, except for mixtures whose components are very disparate in size. A slight modification that remedies this deficiency is introduced and the resummation of the associated virial series is carried out, leading to a new proposal for the equation of state. The case of binary hard sphere mixtures (d = 3) is analysed in some detail.     

Ferrimagnetic coupling in oxamido-bridged Mn(II)Cu(II) compounds: a combined CASPT2 and DDCI study

Multiconfigurational perturbation theory (CASPT2) and difference dedicated configuration interaction (DDCI) are applied to study the ferrimagnetic coupling in an oxamido-bridged Mn(II)Cu(II) molecular species. CASPT2 reproduces the experimental coupling very well. From the partition of the CASPT2 energy, the most important contributions to the coupling are established. Spin populations are calculated with DDCI. The successive improvement of the N-electron wave function allows us to analyse the contributions to the spin delocalization.     

A Popov-theory-based survey on digital control of infinite-dimensional systems with unboundedness

This paper represents a Popov-theory-based assessment of thecurrent status of the digital control of infinite–dimensionalsystems with certain unboundedness in control and/or observation,summarizing some results and indicating which, in the authors'opinion, would be the promising directions for future research.     

An adaptive control scheme for a continuous plant under Known output delay, unmodelled dynamics, and input saturation

This paper deals with robustness of adaptive control of continuoussystems subject to known output delay, input saturation, unmodelledlinear dynamics, and bounded disturbances. A simple gradient-typealgorithm with a relative deadzone is used. The relative deadzoneis built with an estimated contribution of the unmodelled dynamicsto the system output. The basic tool used for stability androbustness analysis is Gronwall's lemma.     

Synchrotron fourier transform infrared microspectroscopy: A new tool to monitor the fate of organic contaminants in plants

FTIR microspectroscopy, with synchrotron radiation as a source, was used for the first time to study changes in plant structure induced by organic contaminants. Sunflower (Helianthus annuus L.) plants were grown hydroponically in the presence of benzotriazole. Changes in the plant structure due to uptake, incorporation, and/or transformation of benzotriazole were observed. False color intensity maps of benzotriazole treated secondary root sections showed changes in plant structure, as well as the presence of aromatic CH peaks due to incorporation of benzotriazole within the plant. The presence of the characteristic benzotriazole CH out-of-plane bending mode suggests that the contaminant aromatic ring remains intact upon the uptake by the plant. Simultaneously, the changes in the lignin structure suggest that the plant suffered damage by the uptake of the benzotriazole. Spectral variations between the untreated and benzotriazole treated sunflowers were uncovered using principal components analysis (PCA). PCA also revealed clustering according to the different benzotriazole treatments.     

Thermal treatment of moolooite

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. Moolooite as the natural copper(II) oxalate mineral is a classic example. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition takes place at 260°C. Evolved gas mass spectrometry shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II) oxalate as compared to the synthetic compound which is the dihydrate. The high resolution thermogravimetry was complimented with hot stage Raman spectroscopy. The temperature at which no intensity remains in the bands assigned to the oxalate vibrations is the upper limit of the stability of the moolooite. This revised version was published online in August 2006 with corrections to the Cover Date.     

A new quasi-optical filter: the reflective polarizing interferometer

Conclusions A new type of optical filter element has been described and tested, offering an alternative frequency response to that of a Fabry-Perot or Michelson interferometer. It is quite compact, mechanically stable, and suitable for cryogenic operation. Use of this device is planned as a sideband filter in a 15 element imaging array receiver for 90–115 GHz.     

On anti-stokes luminescence from Rhodamine 6G in ethanol solutions

Anti-Stokes luminescence form Rhodamine 6G ethanol solutions excited by a He-Ne laser is observed to be strongly temperature dependent. A theoretical model is proposed for the absorption line shape on the long wavelength side of the pure electronic transition which fits the absorption and luminescence data. Vavilov's law is found to hold even when the absorption coefficient is 10^-6 times the peak absorption coefficient for the Rhodamine 6G dye solution. Another luminescence peak at 6650 Å is observed which is attributed to impurity fluorescence. It could not be related to photochemical products.