Gyroscopic control of a rigid body constrained to rotate about a fixed axis

Gyroscopic control of spin rate or orientation of rigid bodies constrained to rotate about fixed axi

Motion of a symmetric rigid body under the action of a body-fixed force

Approximative method for predicting motion of symmetric rigid body subjected to body-fixed forc

Electron Interactions and Scaling Relations for Optical Excitations in Carbon Nanotubes

Recent fluorescence spectroscopy experiments on single wall carbon nanotubes reveal substantial deviations of observed absorption and emission energies from predictions of noninteracting models of the electronic structure. Nonetheless, the data for nearly armchair nanotubes obey a nonlinear scaling relation as a function the tube radius $R$. We show that these effects can be understood in a theory of large radius tubes, derived from the theory of two dimensional graphene where the coulomb interaction leads to a logarithmic correction to the electronic self energy and marginal Fermi liquid behavior. Interactions on length scales larger than the tube circumference lead to strong self energy and excitonic effects that compete and nearly cancel so that the observed optical transitions are dominated by the graphene self energy effects.Comment: 4 page

Regulation of vacuolar H+-ATPase activity by the Cdc42 effector Ste20 in Saccharomyces cerevisiae

In the budding yeast Saccharomyces cerevisiae, the Cdc42 effector Ste20 plays a crucial role in the regulation of filamentous growth, a response to nutrient limitation. Using the split-ubiquitin technique, we found that Ste20 forms a complex with Vma13, an important regulatory subunit of vacuolar H(+)-ATPase (V-ATPase). This protein-protein interaction was confirmed by a pulldown assay and coimmunoprecipitation. We also demonstrate that Ste20 associates with vacuolar membranes and that Ste20 stimulates V-ATPase activity in isolated vacuolar membranes. This activation requires Ste20 kinase activity and does not depend on increased assembly of the V1 and V0 sectors of the V-ATPase, which is a major regulatory mechanism. Furthermore, loss of V-ATPase activity leads to a strong increase in invasive growth, possibly because these cells fail to store and mobilize nutrients efficiently in the vacuole in the absence of the vacuolar proton gradient. In contrast to the wild type, which grows in rather small, isolated colonies on solid medium during filamentation, hyperinvasive vma mutants form much bigger aggregates in which a large number of cells are tightly clustered together. Genetic data suggest that Ste20 and the protein kinase A catalytic subunit Tpk2 are both activated in the vma13Δ strain. We propose that during filamentous growth, Ste20 stimulates V-ATPase activity. This would sustain nutrient mobilization from vacuolar stores, which is beneficial for filamentous growth.The project was supported by Deutsche Forschungsgemeinschaft grant HO 2098/3 to T.H. and NIH grant R01 GM50322 to P.M.K

Kinematics of rigid bodies in spaceflight

Rigid rotating body kinematic equations for use in space flight mechanic

Planar motion of a human being under the action of a body-fixed thrust

Weightless astronaut maneuvering device for directional and attitude control feasibility study using two body system equations of motio

Experimental investigation of planar motions of a human being under the action of a body- fixed thrust

Planar motion of human being subjected to action of body-fixed forc

Pitch and yaw motions of a human being in free fall

Human limb motions for body orientation during free fal