QCD Green functions in a gluon field

We formulate a dressed perturbative expansion of QCD, where the standard diagrams are evaluated in the presence of a constant external gluon field whose magnitude is gaussian distributed. The approach is Poincar{\'e} and gauge invariant, and modifies the usual results for hard processes only by power suppressed contributions. Long distance propagation of quarks and gluons turns out to be inhibited due to a branch point singularity instead of a pole at $p^2=0$ in the quark and gluon propagators. The dressing keeps the (massless) quarks in q qbar fluctuations of the photon at a finite distance from each other.Comment: 21 pages, 7 figures. Minor modifications in text. Version to be published in JHE

Tomato chocolàte virus: a new plant virus infecting tomato and a proposed member of the genus Torradovirus

A new virus was isolated from a tomato plant from Guatemala showing necrotic spots on the bases of the leaves and chocolate-brown patches on the fruits. Structural and molecular analysis showed the virus to be clearly related to but distinct from the recently described Tomato torrado virus (ToTV) and Tomato marchitez virus (ToMarV), both members of the genus Torradovirus. The name tomato chocolàte virus is proposed for this new torradovirus

Test facility and preliminary performance of a 100 kW class MPD thruster

A 260 kW magnetoplasmadynamic (MPD) thruster test facility was assembled and used to characterize thrusters at power levels up to 130 kW using argon and helium propellants. Sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. A thermal efficiency correlation developed by others for low power MPD thrusters defined parametric guidelines to minimize electrode losses in MPD thrusters. Argon and helium results suggest that a parameter defined as the product of arc voltage and the square root of the mass flow rate must exceed .7 V-kg(1/2)-s(-1/2) in order to obtain thermal efficiencies in excess of 60 percent