  The "Wind" spacecraft carrying the Transient Gamma Spectrometer (TGRS) moves
in an extremely elliptical orbit that largely avoids Earth's trapped radiation
belts and albedo gamma-radiation. The TGRS therefore enjoys a relatively low
level of background that is also extremely stable. We show how this stability
enables modeling of the time variability of background lines, which in turn
enables a novel technique of background subtraction to be used in the detection
of transient astrophysical lines. We apply a simple version of this method to
the line at 478 keV that is expected to arise from nucleosynthesis of 7Be in
nearby novae. This search covers the entire southern ecliptic hemisphere during
1995-1997, including five known individual events, and possible undiscovered
individual events. The TGRS design also uses "Wind"'s 3 s rotation period to
modulate signals from the Galactic Center (GC). We use this feature of the
instrument to search for a quasi-constant level of 478 keV emission from the
accumulation of 7Be from several novae that are expected to occur in the
direction of the GC during that isotope's 53 d half-life. We derive upper
limits on the transient (single-nova) emission which improve on previous limits
by about an order of magnitude, and limits on the steady (many-nova) emission
which represent a factor 2 improvement. Only weak limits can be placed on the
key parameters in the nucleosynthesis and ejection of 7Be, however.
