the gauge is fixed up to boundary conditions, and the above results are encouraging 0 One may also argue that direct closed loop calculations will not produce a cosmological term either, simply because dimensional regularization (which respects the gauge invariances) leads to vanishing of tadpole diagrams.

We report final results of a series of measurements of continuum dimuon production in proton-nucleus collisions at Femilab. New results with 6 times more statistics are included. A full description of the apparatus and methods used in the analysis of this series of measurements is given. The sea quark distribution of the nucleon is determined within the context of Drell-Yan and quantum-chromodynamic descriptions of dilepton production in hadron collisions.

The properties of the dimuon enhancement seen in 400-GeV proton-nucleus collisions have been clarified by a threefold increase in data. We find two peaks whose widths are consistent with our resolution: M x = 9.4 GeV with B dcr/dy \ y =o= 1.8 x 10" 37 cm 2 /nucleon and M 2 = 10.0 GeV with B da/dy | y=0 =0 o 7xl0" 37 cm 2 /micleon. Evidence for the possible existence of a third peak near 10.4 GeV is discussed as are the comparisons with the properties of a qq system, where q is a new heavy quark.

Computational chemistry modeling activities that took place as part of a course in physical chemistry are described. The main software tools used by the students were Avogadro and ORCA, which are freely available on the Internet for academic use. Avogadro is molecular visualization software, which can be used not only to prepare input files for a range of computational chemistry software but also to visualize output files from them. ORCA is an ab initio quantum chemistry program containing modern electronic structure methods, such as density functional theory, many-body perturbation, coupled cluster, multireference methods, and semiempirical quantum chemistry methods. Four introductory level computational chemistry activities are described for use in general chemistry and physical chemistry laboratory courses and all are suitable for virtual learning environments. Details of our implementation and the educational value of this work are discussed. In addition, a Student Assessment of their Learning Gains (SALG) survey was conducted after the implementation and the results are reported.