Discharge chamber studies for mercury bombardment ion thrusters

Discharge chamber performance optimization for mercury bombardment ion thruster

Towards the Gravity Dual of Quarkonium in the Strongly Coupled QCD Plasma

We build a "bottom-up" holographic model of charmonium by matching the essential spectral data. We argue that this data must include not only the masses but also the decay constants of the J/psi and psi' mesons. Relative to the "soft-wall" models for light mesons, such a matching requires two new features in the holographic potential: an overall upward shift as well as a narrow "dip" near the holographic boundary. We calculate the spectral function as well as the position of the complex singularities (quasinormal frequencies) of the retarded correlator of the charm current at finite temperatures. We further extend this analysis by showing that the residues associated with these singularities are given by the boundary derivative of the appropriately normalized quasinormal mode. We find that the "melting" of the J/psi spectral peak occurs at a temperature of about 540 MeV, or 2.8 T_c, in good agreement with lattice results.Comment: 13 pages, 9 figure

Coefficient of restitution for elastic disks

We calculate the coefficient of restitution, $\epsilon$, starting from a microscopic model of elastic disks. The theory is shown to agree with the approach of Hertz in the quasistatic limit, but predicts inelastic collisions for finite relative velocities of two approaching disks. The velocity dependence of $\epsilon$ is calculated numerically for a wide range of velocities. The coefficient of restitution furthermore depends on the elastic constants of the material via Poisson's number. The elastic vibrations absorb kinetic energy more effectively for materials with low values of the shear modulus.Comment: 25 pages, 12 Postscript figures, LaTex2

Dormant Cathode Erosion in a Multiple-Cathode Gridded Ion Thruster

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76860/1/AIAA-37031-330.pd

Structure, Biosynthesis, and Occurrence of Bacterial Pyrrolizidine Alkaloids

Pyrrolizidine alkaloids (PAs) are widespread plant natural products with potent toxicity and bioactivity. Herein, the identification of bacterial PAs from entomopathogenic bacteria using differential analysis by 2D NMR spectroscopy (DANS) and mass spectrometry is described. Their biosynthesis was elucidated to involve a non-ribosomal peptide synthetase. The occurrence of these biosynthesis gene clusters in Gram-negative and Gram-positive bacteria indicates an important biological function in bacteria

On asbestos substitutes

Translated from German (Staub Reinhalt. Luft. Feb 1986 v. 46(3) p. 92-96)Available from British Library Document Supply Centre- DSC:9022.381(HSE-Trans--11561)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

On asbestos substitutes

Translated from German (Staub Reinhalt. Luft. Feb 1986 v. 46(3) p. 92-96)Available from British Library Document Supply Centre- DSC:9022.381(HSE-Trans--11561)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo