The development of a hydrogen-based economy would generate a substantial necessity for efficient means of collecting hydrogen with a relatively high purity. Membrane separations play a major role in the separation of hydrogen gas from various gas mixtures, and this article discusses the use of polymeric materials to produce these membranes. After a review of the historical use of polymeric membranes and some background information regarding mechanisms of gas transport in membranes, this article will review the work that has been done in the two major classes of hydrogen separation membranes: hydrogen-selective membranes and hydrogen-rejective membranes. In hydrogen-selective membranes, the very small size of the hydrogen molecule is exploited to allow rapid diffusion of hydrogen through the membrane while excluding other gases. Hydrogen-rejective membranes use the significantly higher sorption of other gases to overcome the advantages of the small size of the hydrogen molecule. The discussion of these two types of membranes will be followed by a presentation of the current state of the art with regard to polymeric membranes for hydrogen separation and a discussion of the predictions for future applications and advancements in this area.

Monoclonal antibodies with group and type specificity for lipopolysaccharide antigens were used in combination with protein A-colloidal gold labeling and transmission electron microscopy to demonstrate the presence of lipopolysaccharide antigens on both the sheathed flagellum and the cel surface of Inaba and Ogawa strains of Vibrio cholerae 0:1. Labeling was associated with the sheath of the flagellum rather than the core, and flagellar cores were not labeled. Flagellum and cell shared a common set of lipopolysaccharide antigens characteristic of the strain serotype.Recent research on the pathogenesis of cholera has concentrated on the factors responsible for adhesion of Vibrio cholerae cells to the intestinal mucosa and the nature of the antigens responsible for stimulating an immune response to infection (1,(4)(5)(6)20). Although the important protective antigens have yet to be unequivocally defined, purified lipopolysaccharide (LPS) has been reported to induce significant protection against cholera in humans and experimental animals (16). The flagellum of V. cholerae has been implicated in pathogenesis of cholera in two ways: with respect to its role as a motility organelle (12,18,25) and with respect to its possible role in adherence of V. cholerae to the host intestinal surface (1). The role of the flagellum as a carrier of the adhesins responsible for attachment to intestinal tissue may be of greater significance than its role in conferring motility (1).While the flagellum of V. cholerae is of possible significance in pathogenesis, its chemical and antigenic composition are poorly understood. The flagellum possesses a membranous sheath covering a core which is similar in structure to naked flagella of other bacteria (7,8). In Vibrio metchnikovii, continuity between the sheath and the outer membrane has been demonstrated (10). The question of whether the flagellar sheath of V. cholerae shares the macromolecular composition of the cell wall outer membrane has not been resolved, however. It has been proposed, on the basis of immunoferritin electron microscopy using polyclonal antibodies to LPS, that the sheath does not contain LPS and that the sheath is thus not a simple extension of the outer membrane (17). However, reports that polyclonal antibodies against somatic 0 antigen and monoclonal antibodies against LPS determinants immobilize motile V. cholerae cells are consistent with the occurrence of LPS in the flagellar sheath (1,14). One way to resolve this problem is to localize LPS directly, utilizing highly specific monoclonal antibodies against LPS antigenic determinants and an electron-dense protein A-gold marker for immunoelectron microscopy. LPS determinants distinguish two major serotypes of V. cholerae 0:1: Ogawa, with determinants A and B, and Inaba, with determinants A and C (13). The establishment of hybrid cell lines producing monoclonal antibodies against such groupand type-specific 0 antigens of V. cholerae 0:1 (13,15) Serotypes were checked routinely by slide agglutination with polytypic (an...

High-performance hybrid materials using carbon molecular sieve materials and 6FDA-6FpDA were produced. A detailed analysis of the effects of casting processes and the annealing temperature is reported. Two existing major obstacles, sieve agglomeration and residual stress, were addressed in this work, and subsequently a new membrane formation technique was developed to produce high-performing membranes. The successfully improved interfacial region of the hybrid membranes allows the sieves to increase the selectivity of the membranes above the neat polymer properties. Furthermore, an additional performance enhancement was seen with increased sieve loading in the hybrid membranes, leading to an actual performance above the upper bound for pure polymer membranes. The membranes were also tested under a mixed-gas environment, which further demonstrated promising results.

PERRY, J. W., and R. F. EVERT. 1983. Histopathology of Verticillium dahliae within mature roots of Russet Burbank potatoes.Can. J. Bot. 61: 3405-3421. Roots of Russet Burbank potatoes (Solanum tuberosum L.) inoculated with Verticillium dahliae Kleb. were examined, primarily with the electron microscope. Penetration hyphae entered epidermal cells directly, apparently aided by hydrolytic enzymes. In most instances, penetration took place without eliciting any structural response. Most hyphae failed to penetrate deeper than the epidermal layer, owing primarily to the formation by exodermal cells of lignitubers that ensheathed the penetration hyphae. Apparently lignitubers were sometimes initiated as callose-like appositions opposite encounter sites. All cortical layers were capable of lignituber production. Few hyphae were encountered within cells deeper than the second cortical layer, and intercellular colonization was not extensive. Nonetheless, vascular infection of unwounded roots occurred. Wilt symptoms were first noted 2 days after hyphae were found in vessel elements of the root. Walls and pit membranes of colonized tracheary elements were coated with an electron-dense substance. As the disease progressed, hyphae invaded all tissues in the vascular cylinder and eventually grew back out into the cortex. The soft-walled tissues were destroyed. In wounded roots many severed vessels contained membranous remnants, conidia, and hyphae that tended to be accumulated at the perforation plates.PERRY, J. W., et R. F. EVERT. 1983. Histopathology of Verticillium dahliae within mature roots of Russet Burbank potatoes.Can. J. Bot. 61: 3405-3421. Les auteurs ont CtudiC, surtout au microscope Clectronique, les racines de pommes de terre "Russet Burbank" (Solanum tuberosum L.) auxquelles le Verticillium dahliae Kleb. avait Ct C inoculC. Les hyphes de pCnCtration entrent directement dans les cellules Cpidermiques, ?i l'aide, apparemment, d'enzymes hydrolytiques. Dans la plupart des cas, la pCn6tration ne provoque aucune rCaction structurale chez l'h6te. La majorit6 des hyphes ne pCnktrent pas plus profondement que la couche Cpidermique, surtout h cause de la formation, par les cellules exodermiques, de "lignitubercules" qui enveloppent les hyphes de pCnCtration. Apparemment, ces lignitubercules sont parfois CbauchCs sous la forme de dCp6ts callosiques aux sites de rencontre. Toutes les couches corticales peuvent produire des lignitubercules. Peu d'hyphes pknktrent h I'intCrieur des cellules situCes plus profondCment que la deuxikme couche corticale et, dans cette region, la colonisation intercellulaire n'est pas considkrable. NCanmoins, l'infection s'Ctend aux tissus vasculaires des racines non blessCs. Les sympt6mes de flCtrissement apparaissent 2 jours aprks que les hyphes se sont introduites dans les ClCments de vaisseaux des racines. Les parois et les membranes des ponctuations des ClCments conducteurs colonisCs parle champignon sont tapissCes parune substance dense aux Clectrons. Avec le progrks de la maladie, les hyphes e...

The structure and development of tissues in potato (Solanum tuberosum L.) root tips colonized by Verticillium dahliae Kleb. were contrasted with those of uninoculated root tips. Within 2 days of inoculation hyphae had penetrated the root cap without eliciting any wall appositions in the root cap cells. Callose-like deposits were found along the walls of protodermal cells bordering the colonized cap cells. Overall, colonized root tips had lost their meristematic appearance owing to increased vacuolation in the cells. In contrast to the normal longitudinal course of primary vascular differentiation, in infected root tips the protoxylem matured in advance of the protophloem. Fifteen days after inoculation the root tips had lapsed into maturity. The endodermis and exodermis extended completely around what was once the apical meristem. Although the xylem had differentiated to within several cell layers of the colonized apex, xylem infection had not occurred in this region. Sieve elements in colonized root tips failed to develop sieve-plate pores.