5,340 research outputs found
Pion electroproduction in a nonrelativistic theory
A nonrelativistic effective theory to describe the electroproduction reaction
of a single pion on the nucleon at leading order in the electromagnetic
coupling is constructed. The framework is tailored to accurately describe the
cusp generated by the pion and nucleon mass differences. The S- and P- wave
multipole amplitudes at two loops for all four reaction channels are provided.
As an application, a new low energy theorem is discussed.Comment: 14 pages, 1 figur
Optimal monetary policy and the sacrifice ratio
Monetary policy - United States ; Econometric models
Spin Effects in a Quantum Ring
Recent experiments are reviewed that explore the spin states of a ring-shaped
many-electron quantum dot. Coulomb-blockade spectroscopy is used to access the
spin degree of freedom. The Zeeman effect observed for states with successive
electron number allows to select possible sequences of spin ground states of
the ring. Spin-paired orbital levels can be identified by probing their
response to magnetic fields normal to the plane of the ring and electric fields
caused by suitable gate voltages. This narrows down the choice of ground-state
spin sequences. A gate-controlled singlet--triplet transition is identified and
the size of the exchange interaction matrix element is determined.Comment: 13 pages, 3 figures, Proceedings of the QD2004 conference in Banf
Endocytosis of the ASGP receptor H1 is reduced by mutation of tyrosine-5 but still occurs via coated pits
The clustering of plasma membrane receptors in clathrin-coated pits depends on determinants within their cytoplasmic domains. In several cases, individual tyrosine residues were shown to be necessary for rapid internalization. We have mutated the single tyrosine at position 5 in the cytoplasmic domain of the major subunit H1 of the asialoglycoprotein receptor to alanine. Expressed in fibroblasts cells, the mutant protein was accumulated in the plasma membrane, and its rate of internalization was reduced by a factor of four. The residual rate of endocytosis, however, was still significantly higher than that of resident plasma membrane proteins. Upon acidification of the cytoplasm, which specifically inhibits the formation of clathrin-coated vesicles but not uptake of the fluid phase marker Lucifer yellow, residual endocytosis was blocked. By immunoelectron microscopy mutant H1 could be directly demonstrated in coated pits. The fraction of wild-type and mutant H1 present in coated pits as determined by immunogold localization correlated well with the respective rates of internalization. Thus, mutation of tyrosine-5 only partially inactivates recognition of H1 for incorporation into coated pits
Are 'Deep' Parameters Stable? The Lucas Critique as an Empirical Hypothesis
For years, the problems associated with the Lucas critique have loomed over empirical macroeconomics. However, relatively little effort has been devoted to testing the empirical importance of this critique. This paper develops a set of tests for small macroeconometric models, especially those used for monetary policy analysis, and implements them on a set of models used extensively in the literature. In particular, I attempt to test the robustness of optimizing versus non-optimizing models to changes in the monetary policy regime.
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