Probing the Light Pseudoscalar Window

Very light pseudoscalars can arise from the symmetry-breaking sector in many extensions of the Standard Model. If their mass is below 200 MeV, they can be long-lived and have interesting phenomenology. We discuss the experimental constraints on several models with light pseudoscalars, including one in which the pseudoscalar is naturally fermiophobic. Taking into account the stringent bounds from rare K and B decays, we find allowed parameter space in each model that may be accessible in direct production experiments. In particular, we study the photoproduction of light pseudoscalars at Jefferson Lab and conclude that a beam dump experiment could explore some of the allowed parameter space of these models.Comment: 22 pages, 4 figure

Niklas Luhmann’s bestuurswetenschappelijke theorie

A critical review of Niklas Luhmann’s Theorie der Venvaltungswissenschaft (Berlin, 1966), is presented. Public administration has so far been the subject of two different kinds of approach; the prescriptive method, based on the construction of purely rational models of organization, and the empirical method which emphasizes the causal explanation and prediction of actual social behaviour in organizational structures. Luhmann attempts to make a synthesis between these two opposing approaches. In modern democratic nations, parliament determines the issues that have to be dealt with. The actual execution is the specific function of the public administrative system. Its decision-making function consists of a standardized process of communication and interaction in which facts are collected, selected and elaborated. This decision-making function of the public administrative system should be rationalized i.e. increased in capacity as much as possible without endangering the continuity of the system. Continuity of the public administrative system is essential for the survival of complex and rapidly changing societies. Therefore when confronted with successive issues of a different nature, the structure of the system may be changed only partially. Empirical knowledge of the social reality yields a range of possible alternatives and their effects. The prescriptive approach will single out that alternative which is most suitable for a rational solution of the problem at hand, while the continuing existence of the system as a whole is guaranteed. It is pointed out that Luhmarm, in his analysis, overlooks the fact that the vested interests of the management of the system may obstruct structural changes. This is related to the essential omission in Luhmann’s theory, viz. the execution of power. A social structure is not only held together by norm internalization based on free choice, but also by the execution of power. By neglecting this basic fact, Luhmann’s theory becomes one-sided and liableto abuse by top management

Characterization of the arcD Arginine:Ornithine Exchanger of Pseudomonas aeruginosa. Localization in the Cytoplasmic Membrane and a Topological Model

The arcDABC operon of Pseudomonas aeruginosa encodes the enzymes of the arginine deiminase pathway and is induced by oxygen limitation. The arcD gene specifies a 53-kDa protein with arginine: ornithine exchange activity. The ArcD protein of P. aeruginosa, like the LysI lysine transporter of Corynebacterium glutamicum, has 13 hydrophobic regions which could span the cytoplasmic membrane. Fusion of a Caa (colicin A) epitope to the N-terminal part of ArcD permitted the localization, by immunoblotting, of the hybrid protein in the inner membrane of P. aeruginosa. Fusion of PhoA (alkaline phosphatase) to the very C terminus of ArcD produced another hybrid protein, which exhibited PhoA activity. Both ArcD hybrid proteins retained arginine transport activity and served to support a topological model which proposes that the N terminus is oriented toward the cytoplasm and the C terminus faces the periplasm. Further ArcD-PhoA fusions were consistent with this model. When the Caa epitope was fused to a C-terminal ArcD fragment consisting of only 5 hydrophobic domains, the resulting hybrid protein could be recovered intact from the inner membrane, suggesting that the C-terminal part of ArcD contains sufficient information for insertion into the membrane. This study illustrates the utility of the Caa epitope to tag membrane proteins