Xenon advances

The wide variation in structure, ranging from complex steroids to the inert monatomic gas xenon, led to several theories of anesthetic action. The mechanism by which inhalation anesthetics manifest their effect is not exactly known. Since they do not belong to one chemical class of compounds, the correlations between structure and activity are also not known. Inhalation anesthetics are nonspecific and therefore there are not specific antagonists. Interaction of inhalation anesthetics with cellular structures can only be described as van der Waals interactions. There are a number of hypotheses that have been advanced to explain the action of inhalation anesthetics however, none of them can adequately describe the entire spectrum of effects caused by inhalation anesthetics. 

Although xenon has the stable octet configuration and is thought to be as inert as other noble gases, several xenon compounds have been prepared. The first xenon compound synthesized by N. Bartlett in 1962 was a red sohd, XePtFe, made by the reaction of xenon with platinum hexafluoride undergoing the following oxidation sequence (Cotton, F. A., Wilkinson G., Murillo, C. A. and M. Bochmann. 1999. Advanced Inorganic Chemistry, ed., pp. 588. New York John Wiley Sons) ... 

Although most of the radiation sources for AAS are LSs, the great advances in detector technology, especially the development of solid-state array detectors and charge-coupled devices (CCDs), have led to the successful application of continuous sources (CSs) for AAS. A modern CS is based on a conventional xenon short-arc lamp that has been optimized to run in the so-called hot-spot mode.9 This discharge mode requires the appearance of a small plasma spot close to the cathode... 

Gas adsorption is the preferred method of surface-area determination. An isotherm is generated of the amount of gas adsorbed against gas pressure, and the amount of gas required to form a monolayer is determined. The surface area can tTien be calculated using the cross-sectional area of the gas molecule. Outgassing of the powder before analysis should be conducted very carefully to ensure reproducibility. Commonly, nitrogen at liquid nitrogen vapor pressure is used but, for low surface-area powders, the adsorbed amounts of krypton or xenon are more accurately found. Many theories of gas adsorption have been advanced, but measurements are usually interpreted by using the BET theory [Brunauer, Emmett, and Teller, J. Am. Chem. Soc., 60,309 (1938)]. 

Xenon NMR spectroscopy has evolved in status over the past two decades from exotic to routine such that it is now used to provide detailed information for an enormous variety of applications. Thus, xenon NMR has become a useful and complementary experiment for the investigation of a large range of materials as will be seen below. Also evident is the growing emphasis on the development and use of hyperpolarized (HP) xenon experiments that can provide much enhanced sensitivity. These experiments have therefore greatly enhanced the utility of xenon NMR studies, and exciting new developments promise even more advances to come. 

Recent advances in creating HP xenon include the work by the Bowers group, who were able to create 67% xenon polarization using 210 W of 795 nm light by combining the output of seven laser diode arrays. Their system is also capable of producing lLatmh at polarizations around 12%. A detailed study of the... 

A variety of new experiments have appeared to explore a large range of materials, from void volumes to engineered materials and biosurfaces. HP xenon imaging has also been used to monitor dynamical processes, such as phase transitions and even breathing. A recent review describes the advances in this area. ... 

Clearly, the future for advances in xenon NMR spectroscopy is very bright. The growing list of important and interesting applications described in this review give an indication of the increasing impact of xenon NMR experiments and point to at least some of the many exciting future developments that may be anticipated. 

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