Electrochemical behaviour of a snake-cage cation-exchange membrane electrolytic sorption and ionic conductivity

Summary The uptake of electrolyte by a snake-cage cation-exchange membrane has been measured by different methods. The experimental data are interpretable by local application of theDonnan law and consequently result from the heterogeneous structure of the membrane. The ionic conductivity measurements confirm these results. No ion-exchange polymer is imprisoned in the superficial layers of the membrane, but it is concentrated in a central zone of maximum capacity. Moreover, the development of continuous and poorly charged pores enhances the structural heterogeneity and lowers the permselectivity. If the snake-cage technique is very versatile to insolubilise many different groups, the structure of the resulting systems must be controlled by an adequate choice of matrix porosity and imprisoned chain length.

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Zusammenfassung Die Elektrolytkonzentration in einer Snake-Cage-Kationenaustauschermembran wird mit verschiedenen Methoden gemessen. Die experimentellen Ergebnisse lassen sich durch lokale Anwendung desDonnan-Gesetzes erklären und folgen demgemäß aus der heterogenen Membranstruktur. Die Leitfähigkeitsmessungen bestätigen die früheren Ergebnisse. Kein Ionenaustauscherpolymeres wird in den oberflächlichen Membranschichten festgehalten, es wird vielmehr in einer zentralen Zone mit der Maximalaustauschkapazität konzentriert. Darüber hinaus vergrößert die Anwesenheit von durchgehenden und schwach geladenen Poren die strukturelle Heterogenität und verkleinert die Permselektivität. Wenn viele verschiedene Gruppen durch die Snake-Cage-Technik unlöslich gemacht werden, was möglich ist, so muß die Struktur der entsprechenden Systeme durch eine angemessene Wahl der Matrix-Porosität und der Längen der festgelegten Ketten kontrolliert werden.

     

Search for a fourth-generation quark more massive than the Z0 boson in p&pmacr; collisions at radicals = 1.8 TeV

We present the results of a search for pair production of a fourth-generation charge -1 / 3 quark (b(')) in sqrt[s] = 1.8 TeV p&pmacr; collisions using 88 pb(-1) of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b(')-->bZ(0) and that the b(') mass is greater than m(Z)+m(b). We studied the decay mode b(')b(');-->Z(0)Z(0)b&bmacr; where one Z0 decays into e(+)e(-) or &mgr;(+)&mgr;(-) and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the sigma(p&pmacr;-->b(')b(');)x[B(b(')-->bZ(0))](2) is established as a function of the b(') mass. We exclude at 95% confidence level a b(') quark with mass between 100 and 199 GeV/c(2) for B(b(')-->bZ(0)) = 100%.     

Immunization with genetically attenuated P52-deficient Plasmodium berghei sporozoites induces a long-lasting effector memory CD8+ T cell response in the liver

Background

The induction of sterile immunity and long lasting protection against malaria has been effectively achieved by immunization with sporozoites attenuated by gamma-irradiation or through deletion of genes. For mice immunized with radiation attenuated sporozoites (RAS) it has been shown that intrahepatic effector memory CD8⁺ T cells are critical for protection. Recent studies have shown that immunization with genetically attenuated parasites (GAP) in mice is also conferred by liver effector memory CD8⁺ T cells.

Findings

In this study we analysed effector memory cell responses after immunization of GAP that lack the P52 protein. We demonstrate that immunization with p52 ^-GAP sporozoites also results in a strong increase of effector memory CD8⁺ T cells, even 6 months after immunization, whereas no specific CD4⁺ effector T cells response could be detected. In addition, we show that the increase of effector memory CD8⁺ T cells is specific for the liver and not for the spleen or lymph nodes.

Conclusions

These results indicate that immunization of mice with P. berghei p52 ^-GAP results in immune responses that are comparable to those induced by RAS or GAP lacking expression of UIS3 or UIS4, with an important role implicated for intrahepatic effector memory CD8⁺ T cells. The knowledge of the mediators of protective immunity after immunization with different GAP is important for the further development of vaccines consisting of genetically attenuated sporozoites.