TO THE COLD OR TO THE WARM? A THERMOELECTRIC EFFECT IN COLLOIDAL SUSPENSIONS
When applying a temperature gradient to an aqueous colloidal suspension,
one observes a flow of its components, or "thermophoresis". Recent
experiments on solutions of lysozyme protein, polystyrene beads, micelles,
DNA, and Ludox particles revealed surprising dependencies on solvent
temperature, acidity, and salinity. In all cases, the solute diffuses to
the warm at low T and to the cold at higher T; a change of sign occurs at
some intermediate temperature. A similar behavior as a function of salt
content was observed for a suspension of charged latex spheres at low
acidity; the particles migrate to the cold at low salinity and to the warm
upon adding NaCl.
In the present paper, we explain these observations in terms of the
thermoelectric effect of the electrolyte: the temperature gradient induces
an electric field of the order of 100 V/m which, in turn, drives the
charged colloidal particles to the cold or to the warm, depending on the
sign of their charge.
***
LB11269
HUNTING QUANTUM BUTTERFLIES
There is a paradox at the heart of quantum mechanics, stemming from the
classical phenomenon of chaos. Large everyday (macroscopic) systems,
which are described by classical mechanics and are generally nonlinear,
can manifest chaos, including sensitive dependence on initial conditions
(the "butterfly effect"). Microscopic systems, e.g. atomic and nuclear
systems, are described by quantum mechanics which is a linear theory,
where chaos is not possible. But classical mechanics is supposed to
emerge from quantum mechanics! Recently, an understanding has evolved
that the theory of open quantum systems, which accounts for local and
random interactions with other nearby systems, is generally non-linear,
and can manifest chaos. However, it has been generally assumed that as
you go to smaller scales, chaos is suppressed. Kapulkin and Pattanayak
present theoretical evidence to the contrary: it is possible to take a
macroscopic system with regular (non chaotic) dynamics, scale it down,
and obtain a mesoscopic system which manifests chaos due to quantum
effects. Scaling the system down further results in a microscopic system
which is strongly quantum mechanical and the chaos manifested in the
transition regime gets washed away by the quantum fluctuations. Thus the
quantum to classical transition is, in general, qualitatively
non-monotonic, and quantum effects can induce chaos in a regular
classical system, contrary to folk wisdom. This should be generic and
beyond fundamental questions of theoretical principle has implications
for quantum control, quantum computing, and nanotechnology. The
transition from quantum to classical behavior continues to yield much
counterintuitive and beautiful physics.
***
LS11482
Oscillating reaction in advanced materials synthesis
The unusual phenomenon of a chemical reaction that oscillates in time has
been observed during synthesis of indium nitride (InN), an advanced
semiconductor material for optoelectronics. Previously, oscillating
chemistry had been found only in reactions of certain molecules in solution
or on surfaces, and in complex living systems such as microbe colonies
and heart muscle. This new oscillatory system is the first one discovered
that involves reactions and transformations between bulk condensed materials
(solids and liquids). When a GaN surface is exposed to a steady vapor flow
of ammonia and an indium compound at high temperature, we observe that a
film of particles forms and then repeatedly transforms back and forth
between crystalline InN and liquid elemental indium, alternately absorbing
and releasing nitrogen to and from the vapor. The oscillatory behavior
indicates that the production of active nitrogen by catalytic decomposition
of ammonia at the surface is key to forming InN. This may help solve the
longstanding problem of synthesis of this important material.
***
LT11043
NEW STRUCTURE(s) OR EFFECTS ON HADRON PRODUCTION
psi(3770) is a bound state of the c and anti-c quarks. It can be
produced in e+e- annihilation. It is believed to be the only observed
structure in the energy range from 3.700 to 3.872 GeV, and almost entirely
to decay to D and anti-D meson pair. However, the BES Collaboration found
that (15+-5)% of psi(3770) does not decay to D and anti-D pair in
assumption of that there is only one psi(3770) in the energy range.
Recently, the BES Collaboration report an anomalous line-shape of cross
sections for e+e- --> hadrons in the energy range, indicating that either
there is likely a new structure in addition to psi(3770) around 3.773 GeV,
or there are some new physics effects reflecting the D and anti-D
production dynamics. This information is important in the understanding of
the QCD and the potential models based on the QCD theory, and even more
important in guiding experimental physicists to search for new kind of
particles such as glueball, hybrid, multiquarks and molecule states
predicted by the QCD theory.
***
ES10437
Hydrostatic and frictionless behavior in loaded granular materials
Granular materials have a reputation for weird phenomena, acting out
somewhere in between solid-like and liquid-like behaviors and sometimes
elsewhere. How loose granular material such as well sorted sands, behave
under loading and unloading cycles reveals unexpected brands of behavior
such as friction free points and stress anisotropies perpendicular to
the loading direction. Hysteresis, consisting of different physical
paths for a system when you load it versus when you unload it, is a well
known phenomenon in rock and soil mechanics. Recent research results, in
two and three dimensional granular systems, have demonstrated that a
peculiar force network supports an externally applied stress. Such a
network consists of a backbone of highly strained grains, that
percolates parallel to the direction of applied stress (positive
anisotropy) and a weak network strained in the perpendicular direction
(negative anisotropy). In this work we find that the unloading stage is
considerably more complex as the two previous subnetworks release the
stress. The most unusual feature of the unloading path is that one
reaches a point, before complete unloading, where the subnetwork stress
anisotropies switch sign and the system is both hydrostatic, like a
liquid, and macroscopically frictionless as seen by an external agent
applying stress, even though the grains themselves interact through
frictional forces. An interplay between microscopic friction and the
stress pattern within the granular medium is proposed as the mechanism
for the emergence of a macroscopic friction.
***
LT11307
Short Ranged Electric Fields Emanating from Molecules: A Novel Approach for Controlling Current Flow in Nanoscale Circuitry at Extreme Packing Densities
We have demonstrated experimentally and theoretically a novel principle for controlling electric currents flowing in the smallest nanoelectronic circuits that can potentially be realized. Our new approach takes advantage of the very short range of the electric fields emanating from molecules. These fields are obvious and forceful to atoms and electrons positioned nearby (within a nanometer), but are effectively cloaked or invisible beyond that. This is not down-sizing of standard methods: The field patterns generated by molecules cannot be emulated by conventional electrodes, not even by the smallest solid state transistor nano-gates currently realized under ideal laboratory conditions. Nanomolecular circuits exploiting this principle should operate without interfering with each other even at the extraordinarily high packing densities achieved by molecular self-assembly. The short range of these electric fields also implies greatly reduced energy dissipation associated with switching of circuits and therefore much less undesirable heating of electronic devices. The extremely small sizes of molecular devices also imply extremely fast communication between active entities. This work opens the way to begin imagining new information processing architectures not previously accessible.
