Research
Roundup
Designing
Accessible Passenger Trains
As
the deadline for compliance with the Americans
with Disabilities Act draws closer, the commuter
and passenger trains used in large swaths of
the United States remain inaccessible to passengers
in wheelchairs. Meanwhile, the elevated platforms
many regional rail systems have erected to address
this problem have created another, forcing bulky
freight shipments off the rails and onto some
of the busiest roadways in the nation.
Dr.
Edward K. Morlok, professor of transportation
and systems engineering, has designed
a new train car that's fully accessible
to disabled passengers, compatible
with freight trains and spacious enough
to carry nearly 40 percent more passengers.
Penn has filed for patent protection.
Problems
arise when two different levels of
platforms are found alongside the
same set of tracks, a situation common
in the northeastern U.S. Older low-level
platforms deny access to disabled
passengers, who cannot mount stairs
to enter cars. Newer high-level platforms
block the passage of freight trains,
funneling truck traffic onto congested
highways.
Dr.
Morlok's answer to this dilemma is
a split-level car divided into three
sections, with the two ends at the
level of a high platform (four feet
above the rails) and the longer middle
portion accessible from lower platforms
(eight inches above the rails). Doors
are situated at both levels, opening
only at the appropriate stations,
and a small lift within the car permits
disabled passengers to move between
levels.
Because
the central portion of the car is
lower, a second level can be added
above it. To fit within railroad height
restrictions in the Northeast, the
double-deck levels are nested together
to yield full headroom over aisles.
The tri-level configuration carries
some 130 passengers, compared to about
94 in current-generation cars with
similarly wide seats.
Dr.
Morlok estimates that by more rapidly
loading and unloading passengers,
his design could shave six percent
off the time it takes a commuter train
to run its route and boost ridership
two to four percent. Because fewer
staffers would be required to assist
passengers as they board and alight,
the new design could slash train staffing
costs by up to a third.
Dr.
Morlok has also developed a second
car design whose vestibule features
a stairwell that can rotate for access
to either high or low platforms. Such
a design would save considerable time
for trains stopping at both types
of platform; currently most such trains
have to be reconfigured manually by
conductors.
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Giant
Self-assembled Liquid Crystal
Lattice
A
new liquid crystal lattice created by scientists at Penn and the University
of Sheffield may be invisible to the naked eye, but it's a giant in its
own way.
Uniting
hundreds of thousands of atoms, this
supramolecular structure is one of
the most complex ever made via self-assembly,
where molecules organize themselves
into larger structures. It's the first
organic compound to assume an intricate
structure previously seen only in
metals such as uranium and various
metal alloys.The work is described
in a paper published on the web site
of the journal Science.
Among
self-assembled structures, bigger
is better. Dr. Virgil Percec, professor
of chemistry, says if this lattice
can attain dimensions equaling the
wavelength of light the material could
represent a new class of photonic
crystals and a new approach to telecommunications.
Such work could also yield molecular-scale
electronics.
To
create these large nanostructures,
Dr. Percec and his colleagues started
with a supersized building block:
a carefully designed, well-defined
and highly branched molecule referred
to as a dendron. When thousands of
these tree-like molecules come together,
they organize themselves, unaided,
into discrete microscopic spheres.
In
the liquid crystal phase, each sphere
consists of 12 tapered dendrons linked
at their narrow end. Dr. Percec and
his colleagues observed 30 of these
globular structures arrange themselves
into a tetragonal lattice whose repeat
unit is a rectangular prism containing
255,240 atoms and measuring 169 by
169 by 88 angstroms. This repeat unit
size is comparable to the crystal
form of some spherical virus particles
isolated from plants.
Using
increasingly sophisticated techniques,
scientists engineer self-assembling
molecules to arrange themselves into
much larger, functioning objects.
The field draws inspiration from nature,
where proteins and cells are genetically
encoded to arrange themselves into
functional entities.
Self-assembly
may prove useful in a wide range of
fields, many involving encapsulation
of materials: drug delivery, adhesives,
pesticides, composites, coatings and
paints, photographic and imaging media,
catalysis, microfabrication and microelectronics.
Dr. Percec's group is now tweaking
the structure of their dendron molecules
so they might assemble into hollow
spheres.
Dr.
Percec is joined in the Science paper
by co-authors Wook-Dong Cho at Penn
and Goran Unger, Yongsong Liu and
Xiangbing Zeng at the University of
Sheffield. The research was funded
by the UK Engineering and Physical
Sciences Research Council and the
NSF.
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Insect
Antibiotics: A Model for
Therapeutic Agents
For
antibiotics, the best way to beat bacterial defenses may be to avoid them
altogether. Researchers at the School of Medicine have discovered that
Cecropin A, a member of a family of antibiotic proteins produced by insects,
may kill bacteria and avoid resistance by entering bacterial cells and
taking control of their genetic machinery.
While
most antibiotics kill bacteria by
attacking critical enzyme systems,
Cecropin A somehow slips inside the
bacteria and turns specific genes
on and off. The findings challenge
conventional thinking on how these
antibiotics function, and may aid
in turning antimicrobial peptides
like Cecropin A into therapeutic agents.
"For
decades, researchers have studied
Cecropin A and focused on its obvious
effects against bacterial cell walls
and membranes. These antibiotics certainly
do disrupt outer structures of the
bacterial cell, but there's much more
to the story," said Dr. Paul
H. Axelsen, associate professor of
pharmacology and infectious diseases. "Before
the bacterial cell dies, Cecropin
A enters the cell and alters the way
its genes are regulated. It's like
sneaking over the castle wall and
opening the gates from the inside.
We need to understand this mechanism
of action because it may explain why
bacteria are unable to develop resistance
to this family of antibiotics."
Dr.
Axelsen's findings were described
in the January issue of the Antimicrobial
Agents and Chemotherapy, a publication
of the American Society for Microbiology.
In their study, Dr. Axelsen and his
colleagues treated E. coli with small
doses of Cecropin A--not enough to
kill the bacteria, but enough to see
what genes are affected when bacteria
are exposed to the antibiotic. They
found that transcript levels for 26
genes are affected, 11 of which code
for proteins whose functions are unknown.
Even more surprising for the researchers,
the genes are not the same as the
ones affected when bacteria experience
nutritional, thermal, osmotic, or
oxidative stress.
Despite
years of research, there remains much
to know about the antibiotics produced
by insects. Cecropin A was discovered
in the Cecropia moth, also known as
the silkworm moth, the largest moth
in North America. Since insects do
not have an immune system as humans
do, they rely on polypeptide antibiotics
like Cecropin A to fight off infections.
These proteins are highly selective--they
readily kill bacteria, but are harmless
to human and other animal cells. Moreover,
bacteria that are susceptible initially
stay susceptible--researchers have
not seen bacteria develop resistance
to their action. For this reason,
these antibiotics offer a potentially
invaluable model for new therapeutic
agents.
This
research was supported by grants from
NIH, American Heart Association, and
from Affymetrix's donation of E. coli
GeneChip Microarrays.
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Women
in Region: Facing Significant
Inequality
The
women's movement has shattered some glass ceilings, but full-time working
women in Philadelphia still earn 25 percent less than men, with the wage
disparity for women in "pink collar jobs" even greater.
Researchers
from Penn and Solutions for Progress
joined leaders from Women's Way in
releasing the Women's Way report, A
Change of Pace: Accelerating Women's
Progress.
According
to the report, women working full-time
in 2001 in the Philadelphia region
of Bucks, Chester, Delaware, Montgomery
and Philadelphia counties earned a
median income of $31,375 while men
working full-time earned a median
income of $42,050, or $10,675 more
than women.
Further,
women were overrepresented in "pink
collar jobs" such as personal
care, health-care support and administrative
support. These occupations represent
the lowest paying jobs in the workforce
with median hourly wages ranging from
$7.40 to $10.18.
Dr.
Dana L. Barron, associate director
of the Alice Paul Center for Research
on Women and Gender, in collaboration
with Laryssa Mykyta, senior policy
analyst with Solutions for Progress,
collected and analyzed data from federal
agencies including the Census Bureau
and the U.S. Department of Labor,
and from published reports.
Their
report covers income and occupations,
poverty and economic security, housing,
responsibility for care giving, work/family
balance, assets and wealth, influence,
aging and retirement and reproductive
rights. It offers policy recommendations
designed to accelerate the pace of
women's progress in achieving fair
and equitable compensation for their
work.
Between
September 2001 and August 2002, researchers
conducted a telephone survey of residents
in the Philadelphia metropolitan area
to determine public attitudes and
priorities. The research team also
interviewed leaders of women's non-profit
groups, directors of community organizations
and academic experts on gender and
wage issues.
Dr.
Barron said that the report definitively
demonstrates that area residents are
aware of gender inequalities and adamant
that their public officials take action
to remedy them. Copies of the report
are available at www.sas.upenn.edu/wstudies/alicepaul.
See
more Research Roundup from other Almanac issues.
Almanac, Vol. 49, No. 25, March 18, 2003
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