The behavior of benzene molecules in ZSM-5 has been studied in detail with the use of diffuse reflectance FT-IR spectroscopy. The infrared difference spectra indicate that benzene molecules have a high selectivity for adsorption first on the most energetic (Brönsted acid) ZSM-5 sites. The existence of at least two adsorbed benzene species has also been confirmed by infrared spectroscopy. Deuterated benzene (C6D6) species located at the ZSM-5 channels and channel intersections are characterized by the C-D stretching vibrations at 2284 and 2276 cm−1, respectively. Since the high symmetry ( D6h) of the adsorbed benzene molecules is preserved, the framework of ZSM-5 may have been distorted. The distortion of the framework of ZSM-5 is also indicated by the red shift of the Si-O (or Al-O) asymmetric stretching vibrations (at ∼1215 cm−1) when adsorbed benzene molecules are present.

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Abstract-The concept of cognitive radio (or secondary spectrum access) is currently under investigation as a promising paradigm to achieve efficient use of the frequency resource. In this paper, we consider a decentralized cognitive radio model based on spectrum leasing, whereby a primary (licensed) user leases its bandwidth for a fraction of time to a network of independent secondary (unlicensed) terminals in exchange for cooperation. On one hand, the primary user decides whether to exploit (space-time coded) cooperation from the network of secondary terminals in order to maximize its own transmission rate. On the other hand, secondary terminals accept to cooperate with the primary only if compensated with a large enough fraction of time for their own transmission, towards the goal of maximizing their rate discounted by the overall cost of transmitted power. The considered model is studied in the framework of Stackelberg games, with the primary and the set of secondary users modelled as the (Stackelberg) game leader and the follower, respectively. Numerical results show that spectrum leasing based on trading secondary spectrum access for cooperation is a promising framework for cognitive radio.

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Solubilization of hydrophilic compounds was examined in liquid 1,1,1,2-tetrafluoroethane (R134a) in the presence of the cationic surfactant trioctylmethylammonium chloride (TOMAC). The absorption spectra of methyl orange in the TOMAC-containing R134a solutions were obtained. Significant blue shifts were observed in comparison with the spectrum of methyl orange in aqueous solution. The shifts decreased as the water-to-surfactant ratio, W0, increased. In addition, spectral measurements confirmed the dissolution of cytochrome c in R134a in the presence of TOMAC. R134a remains as a liquid under mild applied pressure and becomes gas under ambient conditions; it therefore separates from analytes of interest directly without further concentration when used as an extraction solvent. Accordingly, it may be applied to recover valuable hydrophilic substances of low concentration from aqueous solutions.