The NYU team, led by Jasna Brujic, an assistant professor in NYU’s
Department of Physics, developed an innovative way to tabulate the
number of spheres-they created a method for determining how spheres
pack from inside the jar, making it easier to more accurately count
them.
To answer the question of how particles pack in general, the NYU
researchers made a transparent, fluorescent packing of oil droplets in
water, which allowed it to record three-dimensional images and examine
the local geometry of each member of the pack. In other words, what
does a packing look like from the point of view of a grain within-i.e.,
a “granocentric” view?
By tuning the optical lattice
depth or the interaction between cold atoms, a weakly-interacting atomic
bosonic superfluid can be converted into a strongly correlated Mott insulator.
Near the phase boundary, quantum criticality, resembling that of Ising-type
magnetic systems in higher dimensions, is expected to emerge with full
universal behavior. Cold atom researchers in IRG4 have established the first in
situ imaging for bosonic atoms in 2D optical lattices, which provides a
powerful tool to capture the full quantum state of the many-body system, from
the microscopic statistics of site occupancy to the macroscopic thermodynamics. This experimental milestone has also been achieved along with very
interesting findings: observation of the long- sought plateau structure of the
Mott insulator, and the incompressibility of the Mott insulator domains.
New experiments to explore the quantum dynamics of atoms in the quantum
critical regime have shown interesting transport behavior in mass and entropy
flows. In particular, time scales very different from microsopic tunneling and
interaction time scales have been identified in the global equilibration of the
2D system.
Block copolymer/nanoparticle (BCP/NP) composites have attracted interest because of the unique opportunities for tuning the properties of hybrid materials arising from the control of orientation and location of particle fillers within the copolymer matrix. However, quiescent organized block copolymer microstructures are not macroscopically uniform but rather exhibit ‘polycrystal-type’ texture with grain boundary defects that disrupt the long-range periodicity.
In designing new motile materials, much can be learned by studying the
physical mechanisms underlying cell crawling. One important form of
cell crawling is driven by self-assembly of the protein actin. In this
process, energy is supplied and various proteins cooperate to assemble
actin from small proteins into a branched network. We have conducted
the first physically-consistent simulations of this process and have
discovered that the mechanism driving motion of the cell boundary
(modeled in our case by a flat disk) is very simple: the buildup of the
branched actin network behind the disk drives the disk forwards because
the disk is repelled by actin. This is reminiscent of the old joke
about why bagpipe players always walk while they play (to get away from
the noise). Understanding of this mechanism opens the way to the
development of new materials that can move, such as
asymmetrically-coated beads in self-generated concentration gradients.
Silicon/silicon
dioxide is arguably the most important technological interface. With the end of
Moore’s law scaling for silicon fast approaching, alternatives to silicon
dioxide could enable new electronic device architectures. MRSEC researchers
have recently achieved ferroelectric functionality in intimate contact with
silicon by growing SrTiO3 films in an intricate growth process using oxide
molecular-beam epitaxy, producing fully
strained SrTiO3 layers in direct contact with silicon with no
interfacial silicon dioxide. Piezo-force microscopy
sees ferroelectricity in the ultra-thin
SrTiO3 layers. Stable ferroelectric nanodomains, observed at
temperatures as high as 400 K, may form the basis of a new class of
ferroelectric memories, bistable field-effect
transistor devices, and low-power devices operating at room temperature.