SPRING 2003
COLLOQUIA
DEPARTMENT
OF PHYSICS AND ASTRONOMY
Mondays,
11-12:15 in SLH-050
(Colloquium organizer: Mark Gross, mgross@csulb.edu)
Last updated
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February 3
Douglas
Tobias
Dept. of Chemistry, UCI
http://www.chem.uci.edu/people/faculty/dtobias/
THE SALT WATER/AIR INTERFACE
It's saltier than you think
(and
influences the air you breathe)
Aerosols formed from microscopic droplets of water are the sites of many chemical reactions that influence the composition of the atmosphere. The air/water interface at the surface of aqueous aerosol particles is a unique environment for chemistry that does not take place in bulk solution. A full understanding of the kinetics and mechanisms of aerosol chemistry requires a molecular scale picture of structure and dynamics at the air/water interface that is difficult to obtain experimentally. In my talk, after introducing molecular dynamics simulations (numerical solution of equations of motion for a system of particles), I will illustrate the role that these simulations can play in providing new insights into heterogeneous processes in the atmosphere. Specifically, I will present results from simulations of interfaces of alkali-halide solutions. The traditional picture (based on surface tension data), widely accepted for decades, is that ions are repelled from the air/water interface. Our simulations predict that, while the small, non-polarizable fluoride ion is excluded from the interface, in accord with the traditional picture, all of the larger, polarizable halide ions are present at the interface, and bromide and iodide actually have higher concentrations in the interfacial region than in the bulk. I will present preliminary X-ray scattering data that confirm the predictions of the simulations, and I will discuss the physical basis for ion adsorption to the air/water interface, as well as the implications of the new view of salt water/air interfaces for the reactivity of sea salt aerosols in the marine boundary layer (e.g. the coastal region near Long Beach).
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February 10
C. Kwon
CSULB
http://www.cnsm.csulb.edu/faculty/ckwon/
SCANNING
LASER MICROSCOPY
I will report the progress made during the last year
in the Scanning Laser Microscopy program.
The Variable Temperature Scanning Laser Microscopy (VTSLM) technique
measures the spatial distribution images of critical temperature Tc and critical current Jc. A coated conductor of YBa2Cu3O7
is studied using VTSLM. The images taken
at temperatures over which the sample undergoes the superconducting transition
show that there are three distinctive regions.
In the first region, the transport current flows percolatively. Localized superconducting transition
measurements show that Tc is quite uniform
in this region, suggesting that the percolation path is created due to grain
boundaries. The second region exhibits
extremely non-uniform Tc and non-uniform
current flow. Non-uniform Tc of YBCO clearly indicates materials problems,
and it might be due to poor crystalinity or interdiffusion. The
third region has Tc comparable to the
first region; however there the VTSLM signal is much smaller than in the other
regions. We have also mapped the spatial
distribution of the critical current Jc in
superconducting states, and Jc images show
similar features as Tc images. In this talk, we will present the
relationship between grain boundaries and transport current path imaged by
VTSLM.
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February 17
Ken Ganezer
Department of Physics, CSUDH
http://www.csudh.edu/univadv/mediaexpertweb/experts/Physics.htm
http://www.aip.org/physnews/graphics/html/super-k.htm
NEUTRINO
OSCILLATIONS AND COSMIC RAY NEUTRINO
RESEARCH
AT SUPER-K; WHY ALL THE EXCITEMENT?
In recent years the first solid experimental evidence
for physics beyond the standard model has come to light from measurements of
cosmic ray neutrinos at Super-Kamiokande (Super-K),
the Sudbury Neutrino Observatory (SNO), and other similar projects. These data
have brought the new field of lepton mixing to the forefront of particle
physics. Cosmic ray neutrinos, from the Sun, SN 1987A, and yet to be identified
cosmological sources, have also been used to establish neutrino astrophysics.
In this colloquium we outline results from the first five years of Super-K data
on neutrino oscillations and neutrino astrophysics. Other existing and planned
neutrino experiments will be briefly discussed.
It is surprising that we can learn so much about the
smallest and largest objects in the Universe from seemingly innocuous cosmic
ray neutrinos.
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February
24
Shane Ross
Control & Dynamical Systems
Caltech
http://www.cds.caltech.edu/~shane/
Chaotic
Motion in the Solar System:
Mapping the
Interplanetary Transport Network
Where asteroids and comets are concerned, the solar system is more like a
turbulent sea than a shooting gallery. A recent collaboration of workers
from dynamical astronomy, chemistry and fluid dynamics has begun a systematic
study of the chaotic transport of material in the solar system. I will
report our analytical method for describing an asteroid's likelihood of
escaping an orbit around a planet. The result, inspired by work on
transitions between chemical species during reactions, gives researchers a new
tool for analyzing the orbits of the flotsam of the solar system. I will
also describe some work in progress for the analysis of more complicated
orbital situations such as the scattered Kuiper belt,
where we use tools originally designed for use in oceanography.
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March
3
MILLER COLLOQUIUM
Richard
Ellis
Steele Professor of Astronomy, Caltech
Director, Caltech Optical Observatories
http://www.astro.caltech.edu/~rse/
GRAVITATIONAL
LENSING: NATURE’S GIANT TELESCOPES
Ignored for decades after Eddington's verification of General Relativity via the deflection of starlight at the time of a solar eclipse in 1919, gravitational lensing is now one of the most useful tools of the modern cosmologist. In this lecture I will summarize how lensing enables us to map the distribution of dark matter and compare its relative location with respect to that of the radiating baryons, as well as to use its unique magnification properties to gain an early glimpse of the first feeble star-forming systems emerging from the so-called "dark ages". I will discuss the role of future facilities in furthering such studies.
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March 10
Leon Alkalai
Director, Center for Integrated Space
Microsystems
Jet Propulsion Laboratory
California Institute of Technology
http://cism.jpl.nasa.gov/sando/lalkalai.html
DEPENDABLE
COMPUTING FOR SOLAR SYSTEM EXPLORATION
The
firing of Deep Space One’s ion engine
In
this talk, we provide a perspective on one enabling technology aspect of solar
system exploration: Dependable
Computing. Whereas we reflect on the engineering marvels of the Voyager
and other past and present spacecraft, our focus is on the future of solar
system exploration. In particular, we anticipate that solar system missions in
the coming decade will increasingly involve aspects of: a) in-situ exploration
(as in addition to remote sensing); b) advanced surface, sub-surface and aerial
mobility elements such as planetary rovers, surface penetrators
and probes, aerobots, etc.; and c) collecting and
returning samples to Earth. These future mission concepts present a new
engineering and technical challenge for dependable computing in space. Two
aspects are particularly worth noting. First, innovative new power source
capabilities may enable ultra-long life space exploration. Second, all
destinations considered for in-situ exploration of the solar system involve
some aspect of survivability in extreme environments. These conditions include
extreme low-temperatures ranging from Mars, and further out to Jupiter, Europa, Titan, etc. However, suggested explorations of the
Venus surface require survivability in extreme high-temperature environments.
These conditions are further compounded by (in some cases extreme) radiation
exposure as well as hostile atmosphere (including high pressure).
The design of high-performance avionics for autonomous spacecraft control and survivability in extreme environments represents the major challenge for future dependable systems in space. Moreover, future in-situ mobility systems will benefit from the additional technology push towards systems miniaturization and low power. We will describe current on-going efforts for addressing some of these technical challenges for the future of solar system exploration.
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March 17
Melanie
Martin
California Institute of Technology
http://bioimaging.caltech.edu/
MEASUREMENTS
OF RESTRICTED DIFFUSION OF WATER IN TISSUE USING NMR
I
will describe nuclear magnetic resonance measurements of restricted diffusion
of water in biological samples. I will focus on, and discuss the
importance of, measurements of the rates of diffusion apparent at short
diffusion times, in particular using the oscillating gradient spin echo (OGSE)
sequence proposed by Gross and Kosfeld in 1969 and an
imaging form of the sequence, echo planar imaging labeled with oscillating
gradients (EPILOG). Experimental as well as Monte Carlo computer
simulation data obtained with the OGSE sequence in water samples, packed beads
in water, vascular bundles of celery, the core of carrots and in in situ and in vivo rat brain, will be compared and
discussed. Structural information such as surface-to-volume ratios for
water compartments in such samples may be determined from the OGSE
measurements. Applications to disease studies will also be discussed.
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March 24
Fengyuan Yang
http://www.pha.jhu.edu/~fyyang/
SPIN
STRUCTURES IN MAGNETIC THIN FILMS
à from half-metallic ferromagnet to
exchange bias ß
Spin structure in magnetic thin films and
nanostructures is crucial for both fundamental physics and technological
applications, such as spintronics or
magneto-electronics. In this talk, I
will discuss three topics about the spin structures in magnetic thin
films. The first is the intrinsic
magnetic properties in epitaxial films of
half-metallic ferromagnet (FM), CrO2,
which has been predicted to be 100% spin polarized The magnetic switching behavior in CrO2
is significantly different from most ferromagnetic films due to its intrinsic magnetocrystalline anisotropy. Using point-contact Andreev
reflection, we have determined the spin polarization of CrO2 to be
nearly 100%. This is the first and only
experimentally confirmed half-metallic ferromagnet by
transport measurements. The second topic
is the spiraling spin structure in exchange-biased antiferromagnet
(AF). The AF spin structure is the key
to the understanding of exchange bias in FM/AF systems. We designed a trilayer
system of Co/FeMn/Py to investigate the spin
structure in the antiferromagnetic FeMn. A spiral of AF
spins is revealed by magnetometry measurement. The last topic is the oscillatory exchange
bias in exchange-coupled itinerant AF, Cr.
Almost all exchange bias systems studied to date use conventional AFs with localized moments.
Using epitaxial (100)Cr/Py
bilayer, we discovered for the first time an
oscillatory exchange bias with temperature and pronounced effect due to the
spin flip transition in Cr. All of these
phenomena can be attributed to the spin density wave antiferromagnetism
in Cr.
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March 31
CAMPUS
CLOSED – NO COLLOQUIUM
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April 7
Yoseph Bar-Cohen
NDEAA Technologies,
JPL/Caltech/NASA
http://ndeaa.jpl.nasa.gov/nasa-nde/yosi/yosi.htm
ELECTROACTIVE POLYMERS (EAP) AS ARTIFICIAL MUSCLES
Human with bionic muscles is synonymous with science fiction or a
superhuman actor in a TV series. With bionic muscles, the character is
portrayed as capable of strength and speeds that are far superior to
human. Recent development in EAP with large electrically induced strain
may one day be used to make such bionics possible. Meanwhile, as this
technology evolves novel mechanisms that are biologically inspired are expected
to emerge. EAP materials can potentially provide actuation with lifelike
response and more flexible configurations. Even though the actuation
force and robustness require further improvement, there have been already
several reported successes. In this seminar the current and future
efforts will be reviewed.
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April 14
SPRING BREAK
– NO COLLOQUIUM
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April 21
Joseph L. Kirschvink
Professor of Geobiology,
Caltech
http://www.gps.caltech.edu/users/jkirschvink/
MARS, PANSPERMIA, AND THE
ORIGIN OF LIFE:
WHERE DID IT ALL BEGIN?
Recent paleomagnetic
studies on the Martian meteorite ALH84001 have shown that this rock traveled
from Mars to Earth with an internal temperature entirely below 40ºC.
Dynamical studies indicate that the transfer of rocks from Mars to Earth (and
to a limited extent, vice versa) can proceed on a biologically-short
time scale, making it likely that organic hitchhikers have traveled between
these planets many times during the history of the Solar system. These
results demand a re-evaluation of the long-held assumption that terrestrial
life first evolved on Earth.
In this lecture, I will review first the current controversies about
what we do and do not know about the direct fossil record of life in the Solar
System, including early Archean microfossils and stromatolites from Australia and putative magnetofossils in the ALH84001 meteorite.
Finally, I will try to compare the probable environments of the early
Earth with that of early Mars in order to evaluate which of these two bodies,
during the first half-billion years of the solar system, might have produced an
environment most suitable for the origin of life and the evolution of
biochemical electron transport chains based on redox
chemistry.
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April 28
MIKE TIERNEY
Intuitive Surgical, Inc.
http://www.intuitivesurgical.com
ADVANCING THE ART OF MINIMALLY INVASIVE SURGERY
THROUGH TELEROBOTICS
Telerobotics
is the enabling technology that is permitting a wider number of surgical
procedures, classically considered only for open surgery, to now be performed
as minimally invasive surgery (MIS) in today’s operating rooms. Moving such
technology from concept to practice required the resolution of a large number
of diverse technical challenges. From an engineering perspective, this lecture
will focus on the key system design issues that had to be solved to overcome
the limitations of existing MIS techniques, to gain initial FDA clearance, and
to be readily accepted by surgeons.
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May 5
Hong Tang
Caltech
http://nano.caltech.edu/research.html
GIANT PLANAR
HALL EFFECT AND DOMAIN
WALL
DYNAMICS IN (Ga,Mn)As
DEVICES
We have discovered a giant planar Hall
effect (GPHE) in (Ga,Mn)As epilayers that is four orders of magnitude larger than
previously-observed phenomena in metallic ferromagnets.
This effect opens new possibilities for realizing new, robust spintronic sensors and devices. In our present work we have
employed the GPHE to provide the first complete and quantitative
characterization of the in-plane magnetic properties of (Ga,Mn)As. The dominant cubic anisotropy field, as well
as a weak uniaxial anisotropy field, are deduced and
compared with theoretical predictions. Using GPHE sensors we have also realized
direct, real-time monitoring of the propagation of individual magnetic domain
walls (DW) in (Ga,Mn)As
devices. This allows us to explore the nucleation and field-induced propagation
of individual DW within.
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May 12
William M. Gelbart
Department of Chemistry and Biochemistry
UCLA
http://www.chem.ucla.edu/dept/Faculty/gelbart/
PHYSICAL
ASPECTS OF VIRAL INFECTION
Viruses are arguably the
simplest biological systems and yet are highly evolved and exquisitely
effective in performing their task of delivering genetic material to host
cells. In my talk I discuss selected examples of the basic physics
underlying viral "life cycles", including: self-assembly of capsid protein and RNA or DNA into infectious viruses;
passage of viral particles through cell membranes; and calculation and
measurement of the forces and pressures inside viral capsids
which drive the ejection of their genomes.
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Information for speakers
Please plan on reaching campus by about 10 a.m. in order to have time to hit traffic, get lost, park, find and reach my office, and then set up for the talk. Enter campus on State University Drive from Bellflower Blvd. to pick up your day pass at the Visitor’s Kiosk (refer to the maps below). Park in Lot 1 and walk to my office, PH3-114, which is in the hallway connecting PH2 and PH3.
A typical audience consists of ~5-10 faculty and 5-10 (mostly M.S.) students, and they tend to ask a lot of questions both during and after the talk. The colloquia begin at 11 a.m. and we encourage speakers to end their presentation at noon. Most speakers use computer displays, though we have many plastic and even some blackboard talks as well. If you want to show a VCR tape or DVD, or use a slide projector, please let me know in advance.
After the
talk, a handful of us will take you to the ‘Chartroom’ for lunch, if your
schedule permits. Typically lunch ends
about
Mark Gross
Directions:
http://daf.csulb.edu/maps/freeway/index.html
http://daf.csulb.edu/maps/parking/index.html