WASHINGTON, Oct. 20 — Scientists and engineers from around the
world will gather on the shores of Lake Ontario in Rochester, N.Y.
next week to discuss some of the latest breakthroughs in lasers and
optics and their applications to cutting-edge science, the
development of new materials, and medicine.
Journalists are invited to Frontiers in Optics (FiO) 2010/Laser
Science XXVI — the 94th annual meeting of the Optical Society
(OSA), which is being held together with the annual meeting of the
American Physical Society (APS) Division of Laser Science at the
Rochester Riverside Convention Center in Rochester, N.Y., from Oct.
24-28. Registration details are at the end of this press
release.
Many of the presentations at the meeting focus on the most
cutting-edge discoveries in applied optics and fundamental physics.
Some highlights, described below, include:
1) A Technique that Shows Colorful Connections in the
Brain
2) Looking for Osteoporosis with Scattered Light
3) Spotting Suspicious Moles
4) Better Detection for Diagnostics and Biochemical Defense
5) Real-Time Imaging of Stroke Models
6) Direct Laser Cooling of Molecules
7) Making Better Biosensors with Electron Density Waves
8) The Coldest Chemistry
9) Taking a Closer Look at Plaque
10) Best Yet Test of Lorentz Invariance
11) Optofluidics Leads to Better Sensors
Additional research highlights, including new way to treat skin
cancer with LEDs, a novel device for imaging brain activity, and
energy consumption trends in communication networks, can be found
online in the Frontiers in Optics Media Center.
https://www.frontiersinoptics.org/MediaCenter/ConferenceNews/default.aspx
1) A TECHNIQUE THAT SHOWS COLORFUL CONNECTIONS IN THE
BRAIN
The connections between neurons in a young, growing brain are
more dynamic and changeable than previously thought, according to
research based on a new technique that reveals the brain circuitry
of a living mouse.
A neuron looks a bit like a tree: its branches are dendrites,
which accept input and its roots are the axon, which send output.
Where axons and dendrites of different neurons come together, they
can make connections — or synapses — that relay signals and form
circuits in the brain.
To study these connections, scientists have traditionally grown
networks of neurons in petri dishes — but there, networks are
limited in their ability to mimic brain cells in a living,
developing creature. Daniel Kerschensteiner, of Washington
University School of Medicine in St. Louis, is one of the first to
study connections in the nervous system of living mice, by
inserting genes into neurons that cause them to produce fluorescent
molecules.
“The novel thing is that we can label specific pairs of pre- and
post-synaptic cells and their connections in an intact circuit,”
said Kerschensteiner. “No one has really done that before.”
When energized by the imaging technique called two-photon
microscopy, the molecules fluoresce in different colors and reveal
the structure and connectivity of brain circuits.
This approach has already yielded some surprising insights. For
instance, studies of the neurons in the mouse retina have shown
that neural connections can change dramatically fairly late in an
animal’s development — in its second week of life, long after the
arrangement of axons and dendrites has already been laid down.
In ongoing experiments, Kerschensteiner hopes to further refine
science’s understanding of how a developing brain reorganizes its
connections as it grows — as well as the internal mechanisms
behind this rearrangement and how much it is influenced by an
animal’s experiences and external environment.
The presentation, “Imaging the Development of Neural Circuits in
the Mammalian Retina” is at 4 p.m. on Monday, Oct. 25.
2) LOOKING FOR OSTEOPOROSIS WITH SCATTERED LIGHT
Researchers at the University of Rochester in New York are
developing a new way to monitor bone health and search for signs of
osteoporosis, using infrared light. At Frontiers in Optics 2010,
Jason Maher, Andrew Berger, and their colleagues will present
ongoing studies of the effects of steroids on the bones of
mice.
Steroids are commonly prescribed for the treatment of rheumatoid
arthritis. Glucocorticoids reduce inflammation around the joints
and ease pain. But like most treatments, steroids have side
effects. Studies have shown that they raise the risk of developing
osteoporosis.
One way to study this problem is to treat laboratory mice with
steroids and with various interventions meant to counteract the
side effect. A key challenge is how to assess a bone’s structural
integrity. The gold standard, removing the bone and measuring the
amount of force needed to snap it in half, can only be performed by
sacrificing the animal. Standard X-ray techniques can noninvasively
determine bone mineral density, but this has proven to be a poor
predictor of fracture risk in humans with steroid-induced
osteoporosis.
The Rochester team is developing a new technique that promises
to be non-invasive, based on a technique called Raman spectroscopy.
By measuring how light scatters off the materials inside bone, they
have been able to calculate the relative amounts of mineral and
protein matrix of intact bones. They hope to find new and better
indicators of bone strength in the chemical information that Raman
spectroscopy provides about both the bone mineral and collagen
matrix that make up bone.
“Our ultimate goal is to be able to measure the properties of a
bone within an intact mouse limb,” said Berger. “We hope to develop
a better way to spot osteoporosis early in its onset.”
The presentation, “Steroid Induced Osteoporosis Detected by
Raman Spectroscopy” is at 3:15 p.m. on Monday, Oct. 25.
3) SPOTTING SUSPICIOUS MOLES
Most of the spots on our skin are perfectly harmless moles,
collections of cells called melanocytes. But occasionally, these
melanocytes turn cancerous, creating the potentially deadly skin
tumor melanoma.
At Frontiers in Optics 2010, scientists at Duke University in
Durham, N.C., will present a new technique that aims to help
doctors distinguish melanomas from harmless moles using
high-resolution snapshots of suspicious spots.
To visually inspect the surface of the skin, doctors can use a
hand-held lens and a bright light or microscopes and a technique
called dermoscopy. But recent studies have found that diagnoses
based on these images are often incorrect, because only the surface
is visible, and the dangerous changes take place too deep to be
seen. “There’s quite a bit of variability in the diagnoses provided
this way,” said Thomas Matthews, a researcher at Duke. The best way
to diagnose melanoma is still a biopsy — the removal and analysis
of a chunk of tissue from a growth — but even then, experienced
doctors often disagree on the diagnosis. This disagreement leads to
false positives (which force unnecessary procedures and drive up
healthcare costs) or false negatives (which can have fatal
consequences).
Matthews and his colleagues at Duke’s Center for Molecular and
Biomolecular Imaging are adapting a laboratory imaging technique to
provide new information about suspicious moles, both in vivo and in
biopsy specimens. Skin contains two kinds of pigments, or melanins:
pheomelanin, which is reddish or yellow, and eumelanin, which is
dark and brownish. Some studies have suggested that a change in the
ratio of these two pigments could signal that a harmless mole has
turned malignant. Matthews’ two-photon microscopy technique pumps a
small amount of energy into the pigments (using much less power
than a laser pointer), then watches the energy redistribute to give
high-resolution images of their distributions in a spot of
skin.
“No one has been able to look at where different melanins are
organized in skin,” said Matthews. “This opens up a whole new
pathway of looking for melanoma.” The most immediate application
would be to reduce false positives and false negatives in
interpreting biopsies; with further research, the scientists hope
to better define how this information can be used to avoid biopsies
altogether.
The presentation, “Nonlinear High-Resolution Imaging of
Eumelanin and Pheomelanin Distributions in Normal Skin Tissue and
Melanoma” is at 8:45 a.m. on Tuesday, Oct. 26.
4) BETTER DETECTION FOR DIAGNOSTICS AND BIOCHEMICAL
DEFENSE
Current detection methods for chemical and biological molecules
involve using tiny, molecular “labels,” typically fluorescent or
radioactive entities, which can be a time-consuming and expensive
process. A University of Michigan research team headed by Associate
Professor Xudong (Sherman) Fan, recently developed a system for
detecting chemical and biological molecules without labels, and
they expect the technology to have broad applications ranging from
clinical diagnostics to drug development, as well as homeland
security and environmental monitoring for biological and chemical
weapons.
According to Fan, the new method has the additional benefit of
not altering the molecules of interest. “We just measure the
molecules directly,” he says, adding that labeling “is a
time-consuming and costly process… and may affect the biological
functions of the molecule” being examined.
Fan and his colleagues built their system by adapting an optical
sensing device known as a ring resonator, which has greater
sensitivity than traditional optical fiber or waveguide sensors.
The team partnered the ring device with a capillary-based fluidic
system, creating a “unique integration of capillary fluidics with
ring resonator technology,” according to Fan.
The capillary system can be used for the introduction of either
liquid or gas to the sensor, giving the new device a broad spectrum
of potential applications. In a clinical diagnostic setting, for
example, body fluids such as blood and saliva can be used.
Alternatively, vapor analysis can also be performed on exhaled
breath for early and non-invasive diagnosis of diseases such as
cancers. For homeland security and environmental monitoring
purposes, volatile organic compounds, such as explosives, are
typically of interest. Particularly for gaseous compounds, most
current systems suffer from a lack of specificity. The combined
device developed by Fan’s group, however, can be built into a
so-called “micro GC” (gas chromatography), which enables highly
specific identification of compounds.
The talk, “Optical Ring Resonator Based Biological and Chemical
Sensors,” is at 11 a.m. on Tuesday, Oct. 26.
5) REAL-TIME IMAGING OF STROKE MODELS
One of the major impediments to understanding how brain cells
die during a stroke and identifying new ways to protect them has
been the long-standing inability to image strokes, or “ischemic
events” in living tissue. Now researchers at Cornell University,
led by Research Associate Nozomi Nishimura, have developed methods
to induce strokes in animal models and image the events as they
unfold.
“We can see the dynamics of interaction,” Nishimura says, adding
that some neurons most likely die due to interactions with many
different types of cells, including immune system cells, vascular
cells, astrocytes and glial cells. She and her colleagues visualize
intercellular dynamics via two-photon excited fluorescence (2PEF)
microscopy, which is able to image individual cells and
capillaries. Employing relatively long wavelengths of light,
Nishimura and her colleagues have succeeded in imaging at greater
depths into tissue than has been possible to date.
Nishimura and her colleagues have also developed a method to
induce localized lesions within rodent models. They adapted a
technology, femtosecond laser ablation, typically used in
micromachining of solid materials, for a novel biological use. This
ability to induce specific small lesions is particularly important
to creating viable models in which to study the progression typical
of dementia. According to Nishimura, it is becoming clear that many
elderly people suffering from dementia have experienced a series of
microstrokes, triggering cumulative damage. “How is it that these
small bleeds or blood clots affect neurons?” she asks, adding that
the ability to introduce and then image microstrokes in a model
system should shed light on how damage might best be mitigated.
The laser ablation system is also being explored for use in
surgical manipulation and in examining tumor migration,
specifically, how cells shed from tumors might also block blood
vessels.
The presentation, “Nonlinear Optical Tools for Studying
Small-Stroke at Microscopic Scales” is at 8 a.m. on Tuesday, Oct.
26.
6) DIRECT LASER COOLING OF MOLECULES
Cooling molecules with lasers is harder than cooling individual
atoms with lasers. The very process of laser cooling, in which
atoms are buffeted by thousands of photons, was thought by many to
be impossible for molecules since photons, instead of slowing and
cooling the molecules, could actually excite internal motions such
as rotations and vibrations. Consequently, to get cold molecules
one method is to first cool atoms and then combine them into
molecules.
Now Yale physicist David DeMille and his team have developed a
way to cool molecules directly with laser light using three lasers
instead of the two typically needed for atoms. By choosing the
molecular species carefully –they experiment with SrF molecules–
and choosing the photon energies to avoid unwanted excitation of
rotational motion, the cooling process can proceed. In this way,
molecular temperatures of 300 micro-K have been achieved, the
lowest ever for direct cooling of molecules. This temperature
pertains so far to motion along one selected dimension only, much
as for the initial demonstrations of laser cooling for atoms.
While these temperatures are less than a thousandth of a degree
above absolute zero, they are for now orders of magnitude hotter
than the cold molecules that can be made by first chilling
individual atoms and then combining them. With the latter approach,
however, the choice of molecules is presently limited to only those
that can be made with alkali atoms. The SrF molecules used in the
Yale experiment, by contrast, possess an unpaired electron. This
makes them potentially useful as quantum bits or in various studies
of fundamental physics. In addition, the results from DeMille’s
group indicate that laser cooling to yet lower temperatures is
likely possible for SrF and other, similar molecules.
“The technique of laser cooling,” says DeMille, “which has led
to a revolution in atomic physics, has now been shown to also apply
to (at least some) molecules. This significantly expands the range
of molecules for which ultracold temperatures can be reached, which
in turn opens a route to many new scientific applications.”
The presentation, “Laser Cooling of a Diatomic Molecule,” is at
1:30 p.m. on Thursday, Oct. 28.
7) MAKING BETTER BIOSENSORS WITH ELECTRON DENSITY
WAVES
An emerging field with the tongue-twisting name of “optofluidic
plasmonics” promises a new way to detect and analyze biological
molecules for drug discovery, medical diagnostics, and the
detection of biochemical weapons. Investigators at the University
of California, San Diego led by Yeshaiahu Fainman have succeeded in
merging a microfluidics system with plasmonics — sometimes called
“light on a wire” — onto a single platform. Plasmonics is based on
electron waves on a metal surface excited by incoming light
waves.
According to Fainman, tapping the potential of plasmonics for
biomolecule detection systems has been a challenge, because
localized optical field scales are usually much larger than the
molecules in question. In order to make a useful optical biosensor,
he says, “We need to increase the interaction cross-section by
finding ways to localize optical interrogation fields ideally to
the scales comparable to those of biomolecules.” Since that is not
currently possible, he and his team used an approach of integrating
microfluidics and plasmonics on single chips, allowing fluid to
ferry the molecules into the cross-section of the optical
field.
Fainman expects the system to be particularly useful in studying
large arrays of protein-protein interactions for identifying
potential drugs that bind to specific target molecules, which may
lead to earlier cancer diagnoses and faster discovery of new drugs.
Unlike most current methods, optical detection does not require
labeling of molecules with fluorescent or radioactive entities —
labels often hinder interaction by covering up or blocking binding
surfaces.
The new platform also carries the advantage of being high
throughput and multiplexed, offering researchers an opportunity to
examine thousands of arrayed compounds simultaneously, which, he
says, “biologists and physicians get very excited about.”
The presentation, “Optofluidic Nano-Plasmonics for Biochemical
Sensing” is at 4 p.m. on Tuesday, Oct. 26.
8) THE COLDEST CHEMISTRY
Chemical reactions tend to slow down as temperature is lowered,
but this isn’t always true. Deborah Jin,Jun Ye, and their
colleagues at the National Institute of Standards and Technology
(NIST) and the University of Colorado have shown that chemical
reactions can continue even at temperatures just a fraction of a
degree above absolute zero. In recent experiments, they took
diatomic potassium and rubidium molecules, each in their ground
states (lowest-possible energy), and found that when mixed, the
molecules dissociated and combined into KRb — molecules with one
potassium and one rubidium atom.
Furthermore, the reaction rates could be slowed considerably by
applying an electric field, which orients the molecules in such a
way as to suppress chemical reactions. The reason for this is that
the KRb molecules are fermions and obey the Pauli Exclusion
Principle, just like where two electrons of the same quantum energy
and spin are forbidden to lie in a single quantum state –
just operated at the level of whole molecules. When applied
electric fields oriented the KRb molecules so as to have the same
spin state (they would already have the same energy state, being in
the ground state to start with) chemical reactions were greatly
suppressed. NIST physicist John Bohn has now provided the
theoretical underpinnings for the ultracold chemical behavior. He
will describe how spin-dependent chemistry, or “stereodynamics,”
will operate in future experiments.
The Presentation, “Manipulation of Ultracold Chemistry” is at 8
a.m. on Thursday, Oct. 28.
9) TAKING A CLOSER LOOK AT PLAQUE
A team of University of Rochester scientists is using the
technique of Raman spectroscopy to study two common dental plaque
bacteria, Streptococcus sanguis and mutans. The relative balance of
the two may be an indicator of a patient’s oral health and risk for
tooth decay — Streptococcus sanguis is associated with “healthy”
plaque, while mutans is associated with tooth decay.
Raman spectroscopy offers the potential to analyze samples of
the bacterium in a simple, rapid and quantitative manner as
compared to microbiology techniques, including the ability to study
spatial distributions of bacterial species, living or dead, within
samples.
“We’re using Raman spectroscopy to study these oral bacterial
biofilms, essentially observing how two species scatter light into
shifted wavelengths in a unique way. We can then use these
characteristic spectra to identify ‘unknown’ samples of these
species,” says Brooke Beier, a Ph.D. candidate at the University of
Rochester’s Institute of Optics. “Studying the spatial
distributions of the good vs. bad bacteria under various growth
conditions may help scientists determine more effective treatments
to prevent tooth decay.”
With the ability to identify biofilm samples by species, the
researchers can now move on to the study of biofilms grown from a
mixture of liquid cultures, where the two species may interact as
they grow together.
The talk, “Confocal Raman Microspectroscopy of Streptococcus
sanguis and mutans,” is at 9:45 a.m. on Tuesday, Oct. 26.
10) BEST YET TEST OF LORENTZ INVARIANCE
The more crucial a physical law is, the more important it is to
keep testing it. One of the most important laws formulated in the
last century or so is Albert Einstein’s principle of invariance,
which says that there is no preferred reference system or
orientation in the universe. A hypothetical violation of this
principle might come about through the intervention of some
not-yet-known force field. The field would manifest itself by the
simultaneous violation of three basic symmetries in nature, called
CPT: charge conjugation (a symmetry which says that nature treats
matter and antimatter alike), parity inversion (which says that
nature can’t differentiate between left and right), and time
inversion (a symmetry which holds that movies of microscopic
interactions should look alike even if you reverse the order
running from front to back). In other words, looking for violation
of Lorentz invariance is equivalent to looking for violations of
CPT invariance.
Michael Romalis and his colleagues at Princeton look for the
faint magnetic influence the hypothetical field would have on
matter by watching two species of atoms – potassium and
helium-3 – which are contained in a rotating vessel. The
whole lab is of course attached to the Earth, which itself rotates
daily and orbits the Sun. All of these motions, carefully accounted
for, should leave behind a trace of a difference for the two atomic
species if an extra field exists.
The result of the latest round of observations improves by a
factor of 30 the constraint on the existence of the hypothetical
Lorentz-violating field.
“This is a rather dramatic improvement in CPT and Lorentz
tests,” says Romalis. “Our new technique also has the potential for
much larger improvements in the future, so there are more limits to
come.”
The presentation, “New Limit on Lorentz and CPT Violation for
Neutrons,” is at 1:30 p.m. on Thursday, Oct. 28.
11) OPTOFLUIDICS LEADS TO BETTER SENSORS
Optofluidics is the marriage of photonics and microfluidics in a
lab-on-a-chip setting. Only about a decade old, the subject answers
the need for producing all the optical components — lenses,
diffraction gratings, switches, mirrors, microscopes, lasers, and
so forth — needed for processing light waves or photons, but in a
liquid environment, specifically in the fluid-filled channels of a
microfluidic chip.
Andreas Vasdekis, a scientist at the Ecole Polytechnique
Federale de Lausanne, in Switzerland, will report on the effect of
surfactants (chemicals at the surface layer between the solid
channel and the fluid) on producing a number of optical effects,
such as in contriving diffraction gratings for producing laser
light in the fluid, or in producing all-optical switching, or in
sensing and analyzing DNA and other bio-molecules.
The presentation, “Surface Optofluidics” is at 2:30 p.m. on
Tuesday, Oct. 26.