ScienceCache
Vol. 177
July 12, 2004
NANOTECHNOLOGIES HIT A NOT-SO-NANO BUMP
The rage to exploit all things quantum may have hit a snag. Quantum nanorods,
atomic structures that have been heralded as the key to everything
from super-efficient solar cells to an elusive white laser, appear
to have an inherent surface charge that may tarnish their gleaming
image, according to a report by scientists in a recent issue of Physical
Review Letters. “We’ve found that while perfect nanorods
have all this wonderful potential, in reality the current manufacturing
process has a serious flaw that gives the rods a charge, and it is
this charge that we expect will seriously degrade their usefulness,” says
Todd Krauss, assistant professor of chemistry. Quantum rods are lengths
of latticed atoms of cadmium and selenium that ought to have no overall
charge, but Krauss has discovered that while textbook physics says
rods should not have a permanent surface charge, in reality they do.
Ideally, quantum nanorods would be constructed of identical layers
of bonded atoms. In reality, however, the lattice of cadmium and selenium
is skewed, and this imperfect fabrication process creates slightly
varied layers that build up to create large disturbances in the overall
surface charge profile. Imagine a stack of books where one in the middle
is not placed exactly on the one below it; its spine protrudes out
one side and its leafed side is sunken into the stack on the other.
The overhang allows some of the cover of the book to be visible; in
the quantum rod, that visible part of the layer is made of charge-carrying
atoms, and their charge disrupts the overall surface charge neutrality
of the rod. Improperly stack enough layers in the rod and an appreciable
surface charge builds up.
Full story
YOUNGER PATIENTS, WOMEN ANTICIPATE SIDE EFFECTS TO CANCER TREATMENT
Age, gender and educational background influence what side effects a
patient expects from their cancer treatment, according to a study of
938 people published today in the online edition of CANCER. Patients
under 60 expected more side effects than others over 60; women expected
more symptoms than men; and patients with a college education anticipated
more side effects than those who had a high school education. Researchers
suspect the differences between age groups are tied to natural aging. “Some
older people already have seen more symptoms from other illnesses and
take the cancer treatment side effects in stride,” says Maarten
Hofman of the James P. Wilmot Cancer Center. “For example, older
people may have already lost some or all of their hair and don’t
see this cancer-related side effect as a problem.” More and more
literature has found that a patient’s expectation for a side effect,
such as nausea, predicts the development of the symptom. While much time
and effort is expended characterizing the side effects of cancer therapies,
little is known about what side effects patients expect to experience
and what type of patient anticipates them. “We suspect there is
a powerful link between the side effect expectations a patient has and
the experiences they have. If we are able to provide them with more information
and ease their concerns, their cancer treatment experience may be better,” says
Hofman.
Full story
KEEPING SUPER-FAST COMPUTERS OUT OF EACH OTHER’S
WAY
Sun Microsystems Laboratories has donated over $500,000 in computer equipment
to computer scientists in support of efforts to make high-speed computers
run faster. Michael Scott, professor of computer science, will use a
newly donated 16-processor SunFire 6800 machine to develop synchronization
algorithms that allow the processors to coordinate their activities efficiently,
loosening a bottleneck that has plagued multiprocessor machines since
their invention. “One of the ironies of computing is that when
you add more processors, they start to get in each other’s way
and slow things down,” says Scott. “The goal of our research
is to get these multiprocessor machines to share information in ways
that are both correct and fast. A lot of companies use multiprocessors
to manage huge databases, but even desktop computers are starting to
go multi-processor now, making synchronization more important than ever.” Different
processors of a multiple-processor machine often need to read the same
section of memory. If one processor needs to update that memory, synchronization
can ensure that no other processor sees data in an inconsistent, mid-write
state, which could lead to serious errors. Conventionally, the memory
would be “locked” until the writer finishes its update, but
this has the potential to slow down the entire system if the writer is
delayed for any reason. Scott and his students are working with colleagues
in the Scalable Synchronization group at Sun Labs to explore alternatives.
Full story
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