Home' Technology Review : November December 2006 Contents From the Labs
84 FROM THE LABS
TECHNOLOGY REVIEW /
researchers looked for sequences that
had changed significantly between
chimpanzees and humans, indicating
that those changes played a crucial role
in human evolution.
NEXT STEPS: Researchers will try
to better understand the RNA gene s
role in brain development and cogni-
tion by creating a mouse that expresses
the human form of the gene.
Gadgets That Know
Your Next Move
Researchers have developed a model
that predicts people s daily activities
SOU RCE: "Eigenbehaviors: Identifying
Structure in Routine"
Nathan Eagle et al.
MIT Media Lab Vision and Modeling Technical
RESULTS: Using location data, call logs,
and other infor mation collected from
mobile phones, Nathan Eagle and
Sandy Pentland of MIT s Media Labo-
ratory have developed a new data-
analysis technique that, with only
limited initial information, can predict
the daily behavior and determine the
social allegiances of study participants.
By looking at a few early-morning
activities and locations, the research-
ers can forecast a person s remaining
daily activities, associations, and loca-
tions with 79 percent accuracy. They
can also identify group a liations with
96 percent accuracy.
WHY IT MATTERS: As mobile devices
generate increasingly immense
amounts of behavioral data---about
whom we call, where we go, and who
is around us---they could learn to sched-
ule meetings or recommend activities.
But that will require new techniques to
make sense of the data. Current com-
puter models that predict behavior are
complex and sometimes miss patterns
that are simple for humans to see. The
researchers approach can characterize
and predict behavior more easily.
METHODS: During the 2004--2005
school year, the researchers logged
more than 350,000 hours of behavioral
data collected from the mobile phones
of 100 students and faculty members
at MIT. The data included infor-
mation on where participants were,
whom they talked to on the phone,
and which other participants were
nearby. From this information, Eagle
and Pentland extracted fundamental
that succinctly describe a person s or
a group s daily activities. For example,
sleeping late in the mor ning is part of
the same eigenbehavior as going out
that evening. Although the connec-
tion between these two behaviors may
seem obvious to a person, it is di cult
for a computer to spot using traditional
NEXT STEPS: The researchers are
looking beyond individual behav-
iors and group a liations to explore
people s in uences on one another.
They will test how well they can deter-
mine the satisfaction of people work-
ing on projects in groups, with an eye
toward predicting which groups will
be more e cient.
A new device that tightly focuses
laser light could increase the density
of optical data storage
SOU RC E: "Plasmonic Laser Antenna"
Ertugrul Cubukcu et al.
Applied Physics Letters 89: 093120
RESULTS: By building a nano antenna
directly onto a commercial semi-
conductor laser, Ken Crozier and
Federico Capasso of Har vard Uni-
versity were able to focus light with a
wavelength of 830 nanometers to a spot
40 nanometers wide. The experimen-
tal work was done by graduate students
Ertugrul Cubukcu and Eric Kort.
WHY IT MATTERS: Optical discs such
as CDs and DVDs are written and read
using laser light. A smaller wavelength
produces a smaller spot size, which
allows more data to be crammed onto
a disc. For instance, CDs are writ-
ten and read using light with a wave-
length of 780 nanometers; for DVDs,
the wavelength is 650 nanometers, and
for Blu-ray discs, it s 405 nanometers.
That s why Blu-ray discs store so much
data---up to 50 gigabytes for dual-layer
discs. Traditional optical techniques
use mirrors and lenses to further
shrink the spot, but at best they can
shrink it to half the light s wavelength.
The researchers antenna sidesteps
the limits of traditional optics to pro-
duce ultrasmall spots of light that could
increase storage density to about three
terabytes (3,000 gigabytes) on a disc
the size of a CD. Moreover, the fabri-
cation process they developed makes
it easy and inexpensive to integrate the
antenna into a commercial laser.
METHODS: The antenna is made of
two gold-coated nanosize rods sepa-
rated by a 30-nanometer-wide gap.
When light from the laser hits the
nano rods, it applies a force to the elec-
trons in the gold, nudging them out
of place. The electrons oscillate back
and forth, causing electrical charges
to build up on both sides of the gap---
positive charges on one side and nega-
tive charges on the other. The rods and
the gap act as a tiny capacitor, which
effectively concentrates the energy
from the laser light into a spot about
the size of the gap.
A computer simulation of the optical nano
antenna that Harvard researchers have
fabricated shows two gold-coated nano
rods separated by a 30-nanometer gap.
Links Archive September October 2006 January February 2007 Navigation Previous Page Next Page