Findings
Software to Encourage Structural Innovation
A free computer program developed by Hopkins
civil engineering
professor Benjamin W. Schafer allows designers of thin-walled
structures, including buildings and bridges, to test the
structures' stability and safety before a single beam is put into
place.
Currently, civil engineers must adhere to rigid building
codes that severely limit their design options, Schafer says.
These rules were adopted to ensure that structures are safe and
to maintain a level playing field among competitors. "These
highly prescriptive building codes accomplished that, but they
also took away the opportunity for structural innovation,"
Schafer says. "My software can help bring it back by giving
engineers a way to predict buckling for structures that don't
fall within the rules."
Schafer's software, called CUFSM, is available for free
downloading on his Web site
www.ce.jhu.edu/bschafer. --Phil Sneiderman
A New Spin on Frustrated Magnets
Physicists at Johns Hopkins and the National Institute of
Standards and Technology (NIST) have found a surprise lurking at
the heart of geometrically frustrated magnets. The odd class of
materials has tantalized condensed matter physicists for years
with puzzling properties and hopes of new insights into the basic
structure and organization of matter.
The surprise is connected to spin, a characteristic of
electrons and the basis of magnetism in solids. When scientists
cool a magnetic material sufficiently, electronic spins typically
"freeze" into a periodic pattern throughout the material. Spins
on neighboring atoms are usually either parallel or in opposition
(antiparallel). Materials whose crystal structure is formed from
square unit cells can readily achieve spin order, but in
materials with a crystal structure that has triangular
components, it can be geometrically impossible to achieve uniform
global spin order, producing what physicists call a frustrated
magnet.
Seung-Hun Lee, a Hopkins alumnus now working at NIST, and
Hopkins physics professor
Collin Broholm learned how such a
material relieves its frustration by bombarding a frustrated
magnet, zinc-chromite, with neutrons. They found that the spins
organize locally, rather than globally, with hexagonal groups of
six atoms acting together to achieve local magnetic order without
order on larger-length scales.
According to Lee, identification of this new, higher-order
organizing pattern could be helpful to scientists working to
advance their understanding of a variety of scientific topics,
including how high-temperature superconductivity works, how
proteins fold, and how subatomic particles like quarks come
together to form the components of atoms. The scientists reported
on their findings in the August 22 issue of Nature.
--MP