Ion thrusters for electric propulsion: Scientific issues developing a niche technology into a game changer.

The transition from old space to new space along with increasing commercialization has a major impact on space flight, in general, and on electric propulsion (EP) by ion thrusters, in particular. Ion thrusters are nowadays used as primary propulsion systems in space. This article describes how these changes related to new space affect various aspects that are important for the development of EP systems. Starting with a historical overview of the development of space flight and of the technology of EP systems, a number of important missions with EP and the underlying technologies are presented. The focus of our discussion is the technology of the radio frequency ion thruster as a prominent member of the gridded ion engine family. Based on this discussion, we give an overview of important research topics such as the search for alternative propellants, the development of reliable neutralizer concepts based on novel insert materials, as well as promising neutralizer-free propulsion concepts. In addition, aspects of thruster modeling and requirements for test facilities are discussed. Furthermore, we address aspects of space electronics with regard to the development of highly efficient electronic components as well as aspects of electromagnetic compatibility and radiation hardness. This article concludes with a presentation of the interaction of EP systems with the spacecraft.

Homozygosity for the C-->T polymorphism at nucleotide 46 in the 5' untranslated region of the factor XII gene protects from development of acute coronary syndrome.

Recently, a C-->T polymorphism at nucleotide 46 in the 5'-untranslated region of the factor XII (FXII) gene was shown to be associated with lower levels of FXII. To study the impact of this polymorphism on the development of an acute coronary syndrome (ACS), we compared 303 patients with ACS and 227 patients with stable coronary artery disease (CAD). In the latter group, 54.2% of individuals carried wild-type FXII:46C, 37.9% were heterozygous FXII:C46T and 7.9% were homozygous for FXII:46T. In contrast, in the ACS group (n = 303), 54.1% were wild-type FXII:46C, 42.6% were heterozygous FXII:C46T and only 3.3% carried the homozygous FXII:46T genotype. The 2.5-fold lower prevalence of the FXII:46T genotype in patients with ACS could indicate a protective effect on the development of ACS (odds ratio = 0.4, 95% CI 0.1-0.9) in patients with pre-existing CAD.

[Local and systemic humoral immune response to protein I of Neisseria gonorrhoeae]. / Lokale und systemische humorale Immunantwort gegen Protein I von Neisseria gonorrhoeae.

Knowledge of the immune response to natural infection with Neisseria gonorrhoeae is presupposition for the development of a gonococcal vaccine. Pili and protein I have gained importance for a subunite vaccine. A pilus vaccine proved to be ineffective in a field trial due to extensive pilus variability. According to an alternative strategy protein I may represent an important vaccine candidate for a gonococcal vaccine. To study the local and systemic, humoral immune response to N. gonorrhoeae cervical secretion, vaginal fluid and serum from prostitutes and family planning patients were compared by the use of a protein I ELISA. In local secretions and in serum patients in the study group showed significantly higher anti-protein-I-IgA-levels than patients in the control group. In cervical secretion immune response to an acute gonococcal infection consisted of a short lived, significant increase of anti-protein-I-IgA, while anti-protein-I-IgG showed a lower, but longer lasting significant increase. The course of the immune response in vaginal fluid reflected the immune response of cervical secretion at a lower level. In serum antigenic stimulus of a local gonococcal infection resulted in a significant but short lived protein I specific IgG immune response. In local infection with N. gonorrhoeae protein I represents a target antigen of the local and systemic immune response. Clear differences exist between local and systemic humoral immune response in the protein I reactive immunoglobulin class and in the course of reactivity. In the future it may be possible to define epitopes on protein I which induce protective immunity.