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Stents and flow diverters have revolutionized the treatment of cerebrovascular disease. Guglielmi coils, flexible microcatheters, and first-generation intracranial stents, such as Neuroform (Stryker Neurovascular) and Enterprise stents (Codman/DePuy-Synthes), have paved the way for the development of the Pipeline Embolization Device (PED) (ev3/Covidien/Medtronic) and other endovascular approaches. This review discusses the historical development of flow diverter technologies from the PED to similar devices, such as the Surpass stent (Stryker Neurovascular), the Flow-Redirection Endoluminal Device (FRED; MicroVention, Inc.), the SILK stent (Balt Extrusion), and the p64 Flow Modulation Device (Phenox). In addition, the potential use of drug-eluting stents and various bioresorbable scaffolds (e.g., poly-l-lactic acid, magnesium), new developments in stent material (e.g., thin-film nitinol), design (e.g., biocompatible polymers, embedded microcircuitry, flow models), and potential applications for flow diverters will be considered. Endovascular treatment of cerebrovascular disease is rapidly advancing via continued development of new technology.

This is certainly the most important book dealing with gas and liquid chromatography that has appeared for many years. Two-dimensional (2D) chromatography dates back almost to the beginnings of the modern era of chromatography, and 2D GC systems have been used since the 1960s. Indeed, Deans who was the first to publish pneumatic switching, believed that all GC problems at that time could be solved by multiple column combinations. The idea of comprehensive 2D chromatography (where all peaks from one column pass to a second, different column) dates back 20 years, but it is only within the last 10 years that it has been taken up by a few enthusiasts most of whom appear as contributors to this book. In particular the editor, Mondello, appears as a co-author in no less than six of the 12 chapters. The potential advantages of comprehensive 2D chromatography are clear, but the practical problems are formidable and this book does not disguise this fact. After a short introductory chapter to set the scene, the book properly starts with a chapter on theoretical aspects of multidimensional gas chromatography by Blumberg. This chapter reminded me of my student course on thermodynamics—after a year of lectures and some 230 equations I was little the wiser. The author manages 91 equations in 46 pages, but in fairness he does try hard to stress the conclusions of his work by inserting paragraphs in italics that outline the practical significance of his theoretical analysis. It is worth quoting a slightly condensed version of his concluding italic paragraph—‘‘GC x GC has the potential to provide at least one order of magnitude larger peak capacity than 1D GC. When the hardware problems are solved the separation performance will be out of reach of any known alternative GC technique. Further significant increase in peak capacity can be obtained by improved data analysis’’. The next chapter deals with the theoretical aspects of multidimensional LC, but fortunately this is considerably simpler than the preceding chapter (a mere 27 equations in 26 pages!). Chapter 4 deals with more practical aspects of comprehensive 2D GC, in particular with the various ‘‘modulators’’ that have been developed. The modulator is the device that samples at short time intervals the peaks emerging from the first column and sends them to the second column. To get reliable determination of peak area at least ten data points per peak should be collected and this places severe demands on the modulator (and also on the detector and data handling system). Indeed the performance of the modulator is the most important of the ‘‘hardware problems’’ touched on in Blumberg’s summary quoted above. Chapter 5 by Seeley describes what seems to me to be possibly the best solution of the modulator problem using flow modulation, since it is by far the least demanding of equipment and operating costs although as always there are E. R. Adlard (&) Burton, South Wirral, UK e-mail: chromatographia@springer.com