Newsbriefs

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University shows surplus for second straight year
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     The university closed out budget year 1995 with a small
surplus, its second straight after finishes in the red four out
of the previous five years.
     The $6 million surplus--admittedly a razor-thin margin,
percentage-wise, in a total budget of nearly $1.5 billion--was
nevertheless nearly $11 million better than the small deficit the
university had projected when fiscal 1995 started in July 1994.
     The university's chances of recording a third straight
surplus in the current budget year are far from certain, Eugene
S. Sunshine, senior vice president for administration, reported
to the trustees at their October meeting. 
     Threats to federal funding and changes in the health care
marketplace, which affect the university's clinical care
revenues, are both causes for concern, Sunshine said. The
university's 1996 fiscal year runs through June.
     Below-budget spending accounted for about two-thirds of the
$11 million spending in fiscal 1995, with better-than-expected
revenues making up the rest.
     "This is a wonderful performance," interim president Daniel
Nathans said at a meeting of deans and senior administrators a
week before the trustee meeting. 
     The $11 million improvement from the budgeted deficit  was
about evenly divided between the Applied Physics Laboratory and
the rest of the university. APL accounted for roughly 30 percent
of university spending.


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Lazer light 'tweezers': Magic meets physics
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     A Hopkins biomedical engineer is levitating particles within
living cells, pulling on a cell's membranes and even playing
tug-of-war with protein molecules--without ever touching them or
freeing them from a sterile container under a microscope.
     What seems like magic is old-fashioned physics, using light
from a 10-watt Nd:YAG laserlike "tweezers" to grab hold of
cellular particles.
     "Light has momentum, and it can move objects," said Scot
Kuo, an assistant professor of biomedical engineering. "The force
is very, very weak. It can't detach an entire cell. But the laser
light is strong enough to move single molecules within cells."
     The Hopkins optical tweezers--also known as a single-beam
optical gradient force trap--operates by a joystick, and users
can watch the magnified image of the microscopic action on a
video monitor.
     "The ability to go hands-on inside a cell is something
researchers have wanted for a very long time," Kuo said. "With
the optical tweezers, they have that capability."
     Kuo said the device he built--there are others available
commercially--depends on the tendency of molecules to seek the
center of a focused light beam. The laser's momentum is enough to
move these particles once they are inside the beam.
     Kuo, who published a practical guide to laser tweezers in a
recent issue of the Journal of the Microscopy Society of America,
is using the device to study subcellular movement, particularly
of microtubules, long chains of protein molecules that help
maintain the cell's shape. Other proteins called "molecular
motors" carry substances to various destinations within the cell,
Kuo said. For example, the tubules move chromosomes during cell
division so that each daughter cell gets an equal share of genes.
Kuo studies a molecular motor called kinesin.