THE synthesis of mesoporous siliceous solids with large-diameter channel apertures (25–100 A) has greatly expanded the capabilities of heterogeneous catalysis1–7 The large apertures in such mesoporous silicas can, for example, be modified by framework substitution to create highly selective catalysts4,5 Here we show that direct grafting of an organometallic complex onto the inner walls of mesoporous silica MCM-41 (ref 1) generates a shape-selective catalyst with a large concentration of accessible, well spaced and structurally well defined active sites Specifically, attachment of a titanocene-derived catalyst precursor to the pore walls of MCM-41 produces a catalyst for the epoxidation of cyclohexene and more bulky cyclic alkenes

Heterogeneous catalysts obtained by grafting metallocene complexes onto mesoporous silica

The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

Among the fundamental goals of microbial ecology is the development of methods that will enable the identification and counting of the important microorganisms in nature, the determination of their physical and chemical microenvironment, and the analysis of their metabolic processes and interactions. Due to the small size of the organisms, much effort has been devoted to the development of high-resolution techniques for the observation and understanding of the world of bacteria on a microscale. Scanning and transmission electron microscopy and fluorescent staining, immunofluorescence and other techniques for light microscopy have been the most successful in terms of reaching a high spatial resolution. With respect to our understanding of the microbial microenvironments and of the nature of the microorganisms that carry out the measured metabolic activities, there is still a long way to go. Most chemical and radiotracer techniques in use today operate on a centimeter or at best on a millimeter scale and in most cases their results cannot be directly related to the relevant microorganisms. One notable exception to this is the combined use of autoradiography and fluorescence microscopy on microbial communities.

Microelectrodes: Their Use in Microbial Ecology

Porous silicon in drug delivery devices and materials

Publisher Summary This chapter discusses the current patterns and perspectives in organolithium chemistry, including the structures of organonitrogenlithium (N-Li) compounds. The chapter explains the compounds with N-Li bonds. These are chiefly lithium imides [iminolithiums (RR’C=NLi) n ] and their complexes with added Lewis bases (L), and lithium amides [amidolithiums (RR’NLi) n ] and their complexes. For the lithium amide species, particularly, only those whose R,R’ groups that do not contain additional functionalities are described—that is, the R,R’ groups remain largely uninvolved with lithium centers. These species are termed “simple” lithium amides. N-Li compounds and, particularly, lithium amides (R 2 NLi) are widely used both in organic and in organometallic syntheses. For the former, these strong bases are employed as proton abstractors to generate new organolithiums. Although synthetic uses have dominated the interest in N-Li compounds, the chapter focuses on the structures. Most of the physical properties of organolithium compounds (the marked exception being conductance) arise, because of the overall size and shape of the units making up these materials and the nature of the peripheries of these units. The basic structural building block of any organolithium is an ion pair, R – L + . The identities and structures of complexed organolithiums are of particular importance.

Structures of Organonitrogen—Lithium Compounds: Recent Patterns and Perspectives in Organolithium Chemistry

INERT ATMOSPHERE TECHINQUES. Bench--Top Inert--Atmosphere Techniques. Inert--Atmosphere Glove Boxes. Inert Gases and Their Purification. Purification of Solvents and Reagents. Vacuum Line Design and Operation. Pumps for Rough and High Vacuum. Pressure and Flow Measurement and Leak Detection. Joints, Stopcocks, and Valves. Specialized Vacuum--Line Equipment and Operations. Metal Systems. Metal Systems. Appendixes. Index.

D. F. Shriver

Papers

The manipulation of air-sensitive compounds