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## New insight into cataract formation -- enhanced stability through mutual attraction

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 24/08/2007

Relevância na Pesquisa

55.57%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Materials Science#Condensed Matter - Statistical Mechanics

Small-angle neutron scattering experiments and molecular dynamics simulations
combined with an application of concepts from soft matter physics to complex
protein mixtures provide new insight into the stability of eye lens protein
mixtures. Exploring this colloid-protein analogy we demonstrate that weak
attractions between unlike proteins help to maintain lens transparency in an
extremely sensitive and non-monotonic manner. These results not only represent
an important step towards a better understanding of protein condensation
diseases such as cataract formation, but provide general guidelines for tuning
the stability of colloid mixtures, a topic relevant for soft matter physics and
industrial applications.; Comment: 4 pages, 4 figures. Accepted for publication on Phys. Rev. Lett

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## Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 12/09/2013

Relevância na Pesquisa

55.58%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Condensed Matter - Statistical Mechanics#Quantum Physics

Einstein realised that the fluctuations of a Brownian particle can be used to
ascertain properties of its environment. A large number of experiments have
since exploited the Brownian motion of colloidal particles for studies of
dissipative processes, providing insight into soft matter physics, and leading
to applications from energy harvesting to medical imaging. Here we use
optically levitated nanospheres that are heated to investigate the
non-equilibrium properties of the gas surrounding them. Analysing the sphere's
Brownian motion allows us to determine the temperature of the centre-of-mass
motion of the sphere, its surface temperature and the heated gas temperature in
two spatial dimensions. We observe asymmetric heating of the sphere and gas,
with temperatures reaching the melting point of the material. This method
offers new opportunities for accurate temperature measurements with spatial
resolution on the nanoscale, and a new means for testing non-equilibrium
thermodynamics; Comment: 5 pages, 4 figures, supplementary material available upon request

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## Thermotropic nematic order upon nano-capillary filling

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 05/04/2013

Relevância na Pesquisa

55.57%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Physics - Chemical Physics

Optical birefringence and light absorption measurements reveal four regimes
for the thermotropic behavior of a nematogen liquid (7CB) upon sequential
filling of parallel-aligned capillaries of 12 nm diameter in a monolithic,
mesoporous silica membrane. No molecular reorientation is observed for the
first adsorbed monolayer. In the film-condensed state (up to 1 nm thickness) a
weak, continuous paranematic-to-nematic (P-N) transition is found, which is
shifted by 10 K below the discontinuous bulk transition at T_IN=305K. The
capillary-condensed state exhibits a more pronounced, albeit still continuous
P-N reordering, located 4 K below T_IN. This shift vanishes abruptly on
complete filling of the capillaries, which we tentatively trace to a 10 MPa
tensile pressure release associated with the disappearance of concave menisci
in the confined liquid.; Comment: 6 pages, 3 figures

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## Polymorphism of the glass former ethanol confined in mesoporous silicon

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 12/05/2010

Relevância na Pesquisa

55.59%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Disordered Systems and Neural Networks#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Physics - Chemical Physics

X-ray diffraction patterns of ethanol confined in parallel-aligned channels
of approx. 10 nm diameter and 50 micrometer length in mesoporous silicon have
been recorded as a function of filling fraction, temperature and for varying
cooling and heating rates. A sorption isotherm, recorded in the liquid state,
indicates a three monolayer thick, strongly adsorbed wall layer and a capillary
condensed fraction of molecules in the pore center. Though the strongly
adsorbed film remains in an amorphous state for the entire temperature range
investigated, the capillary condensed molecules reproduce the polymorphism of
bulk solid ethanol, that is the formation of either crystalline or glass-like
states as a function of cooling rate. The critical rate necessary to achieve a
vitrification in the mesopores is, however, at least two orders of magnitude
smaller than in the bulk state. This finding can be traced both to pure
geometrical constraints and quenched disorder effects, characteristic of
confinement in mesoporous silicon.; Comment: 6 pages, 4 figures

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## From adhesion to wetting of a soft particle

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/09/2013

Relevância na Pesquisa

55.57%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Physics - Chemical Physics#Physics - Classical Physics

Using a thermodynamical approach, we calculate the deformation of a spherical
elastic particle placed on a rigid substrate, under zero external load, and
including an ingredient of importance in soft matter: the interfacial tension
of the cap. In a first part, we limit the study to small deformation. In
contrast with previous works, we obtain an expression for the energy that
precisely contains the JKR and Young-Dupr\'e asymptotic regimes, and which
establishes a continuous bridge between them. In a second part, we consider the
large deformation case, which is relevant for future comparison with numerical
simulations and experiments on very soft materials. Using a fruitful analogy
with fracture mechanics, we derive the exact energy of the problem and thus
obtain the equilibrium state for any given choice of physical parameters.; Comment: Accepted for publication in Soft Matter

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## Inhomogeneous Relaxation Dynamics and Phase Behaviour of a Liquid Crystal Confined in a Nanoporous Solid

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 19/04/2015

Relevância na Pesquisa

55.59%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Physics - Chemical Physics

We report filling-fraction dependent dielectric spectroscopy measurements on
the relaxation dynamics of the rod-like nematogen 7CB condensed in 13 nm silica
nanochannels. In the film-condensed regime, a slow interface relaxation
dominates the dielectric spectra, whereas from the capillary-condensed state up
to complete filling an additional, fast relaxation in the core of the channels
is found. The temperature-dependence of the static capacitance, representative
of the averaged, collective molecular orientational ordering, indicates a
continuous, paranematic-to-nematic (P-N) transition, in contrast to the
discontinuous bulk behaviour. It is well described by a Landau-de-Gennes free
energy model for a phase transition in cylindrical confinement. The large
tensile pressure of 10 MPa in the capillary-condensed state, resulting from the
Young-Laplace pressure at highly curved liquid menisci, quantitatively accounts
for a downward-shift of the P-N transition and an increased molecular mobility
in comparison to the unstretched liquid state of the complete filling. The
strengths of the slow and fast relaxations provide local information on the
orientational order: The thermotropic behaviour in the core region is
bulk-like, i.e. it is characterized by an abrupt onset of the nematic order at
the P-N transition. By contrast...

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## Stable circulation modes in a dual-core matter-wave soliton laser

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 16/05/2006

Relevância na Pesquisa

65.49%

We consider a model of a matter-wave laser generating a periodic array of
solitary-wave pulses. The system, a general version of which was recently
proposed in Ref. [5], is composed of two parallel tunnel-coupled cigar-shaped
traps (a reservoir and a lasing cavity), solitons being released through a
valve at one edge of the cavity. We report a stable lasing mode accounted for
by circulations of a narrow soliton in the cavity, which generates an array of
strong pulses (with 1,000 - 10,000 atoms in each, the array's duty cycle ~ 30%)
when the soliton periodically hits the valve.; Comment: J. of Physics B: At. Mol. Opt. Physics, in press

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## Rotational microrheology of Maxwell fluids using micron-sized wires

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 16/12/2013

Relevância na Pesquisa

55.58%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Mesoscale and Nanoscale Physics#Condensed Matter - Materials Science#Condensed Matter - Statistical Mechanics

We demonstrate a simple method for rotational microrheology in complex
fluids, using micrometric wires. The three-dimensional rotational Brownian
motion of the wires suspended in Maxwell fluids is measured from their
projection on the focal plane of a microscope. We analyze the mean-squared
angular displacement of the wires of length between 1 and 40 microns. The
viscoelastic properties of the suspending fluids are extracted from this
analysis and found to be in good agreement with macrorheology data. Viscosities
of simple and complex fluids between 0.01 and 30 Pa.s could be measured. As for
the elastic modulus, values up to ~ 5 Pa could be determined. This simple
technique, allowing for a broad range of probed length scales, opens new
perspectives in microrheology of heterogeneous materials such as gels, glasses
and cells.; Comment: to appear in Soft Matter

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## The Nature of Superfluidity in Ultracold Fermi Gases Near Feshbach Resonances

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

55.58%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Quantum Gases#Condensed Matter - Strongly Correlated Electrons#Condensed Matter - Superconductivity

We study the superfluid state of atomic Fermi gases using a BCS-BEC crossover
theory. Our approach emphasizes non-condensed fermion pairs which strongly
hybridize with their (Feshbach-induced) molecular boson counterparts. These
pairs lead to pseudogap effects above $T_c$ and non-BCS characteristics below.
We discuss how these effects influence the experimental signatures of
superfluidity.; Comment: 4 pages, 3 figures, submitted to PRA Rapid Communications;
introduction rewritten, figure replaced

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## Formation of soliton trains in Bose-Einstein condensates as a nonlinear Fresnel diffraction of matter waves

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 13/10/2003

Relevância na Pesquisa

65.49%

The problem of generation of atomic soliton trains in elongated Bose-Einstein
condensates is considered in framework of Whitham theory of modulations of
nonlinear waves. Complete analytical solution is presented for the case when
the initial density distribution has sharp enough boundaries. In this case the
process of soliton train formation can be viewed as a nonlinear Fresnel
diffraction of matter waves. Theoretical predictions are compared with results
of numerical simulations of one- and three-dimensional Gross-Pitaevskii
equation and with experimental data on formation of Bose-Einstein bright
solitons in cigar-shaped traps.; Comment: 8 pages, 3 figures

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## Light-matter interaction in Mie nanolasers

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

65.49%

By deriving a three dimensional vector set of Maxwell-Bloch equations, we
report on an ab-initio investigation of a spherical Mie nanolaser. Parallel
numerical simulations predict a rich physical scenario, ranging from a
nontrivial vectorial energy-matter interplay in the initial stage of evolution
to mode competition and dynamical frequency pulling effects. Application of
these effects could favor the realization of nonlinearly-controlled
largely-tunable nanolaser devices.; Comment: Slightly revised version with some typos corrected and figure 3
changed. 4 pages, 5 figures

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## Hydrodynamic effects in driven soft matter

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/03/2012

Relevância na Pesquisa

65.49%

Recent theoretical works exploring the hydrodynamics of soft material in
non-equilibrium situations are reviewed. We discuss the role of hydrodynamic
interactions for three different systems: i) the deformation and orientation of
sedimenting semiflexible polymers, ii) the propulsion and force-rectification
with a nano-machine realized by a rotating elastic rod, and iii) the
deformation of a brush made of grafted semiflexible polymers in shear flows. In
all these examples deformable polymers are subject to various hydrodynamic
flows and hydrodynamic interactions. Perfect stiff nano-cylinders are known to
show no orientational effects as they sediment through a viscous fluid, but it
is the coupling between elasticity and hydrodynamic torques that leads to an
orientation perpendicular to the direction of sedimentation. Likewise, a
rotating stiff rod does not lead to a net propulsion in the Stokes limit, but
if bending is allowed an effective thrust develops whose strength and direction
is independent of the sense of rotation and thus acts as a rectification
device. Lastly, surface-anchored polymers are deformed by shear flows, which
modifies the effective hydrodynamic boundary condition in a non-linear fashion.
All these results are obtained with hydrodynamic Brownian dynamics simulation
techniques...

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## Metastabilities in vortex matter

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/12/1999

Relevância na Pesquisa

65.49%

We extend the classical theory for supercooling across first order phase
transitions to the case when both density and temperature are control
variables. The observable region of metastability then depends on the path
followed in this space of two variables. Since the density of vortex matter in
superconductors can be easily varied over a wide range by varying applied
field, it is ideal for experimental tests. We found, in our studies on the
`peak effect' in the mixed state of superconducting CeRu$_2$, supercooled
states whose observable region of metastability depends on the path followed in
(H,T) space, consistent with our predictions. We also discuss phenomena in hard
superconductors that are well understood within Bean's critical state model. We
conclude that the path dependence of metastablity associated with hindered
kinetics may be opposite to that predicted for metastability associated with
supercooling across a first order transition.; Comment: Submitted to DAE(India) Solid state physics symposium. 11
pages(preprint) and 2 figures

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## Particle Density Distributions in Fermi Gas Superfluids: Molecular Boson Effects

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

55.6%

#Condensed Matter - Soft Condensed Matter#Condensed Matter - Quantum Gases#Condensed Matter - Statistical Mechanics#Condensed Matter - Strongly Correlated Electrons#Condensed Matter - Superconductivity

We show how to describe the $T \neq 0$ behavior associated with the usual
BCS- Bose Einstein condensation (BEC) crossover ground state. We confine our
attention here to the BEC and near-BEC regime where analytical calculations are
possible. At finite $T$, non-condensed fermion pairs must be included, although
they have been generally ignored in the literature. Within this BEC regime we
compute the equations of state for the one and two channel models; these two
cases correspond to whether Feshbach resonance effects are omitted or included.
Differences between these two cases can be traced to differences between the
nature of a Cooper pair and bosonic condensate. Our results are also compared
with the Gross Pitaevskii equations of state for true bosons. Differences found
here are associated with the underlying fermionic character of the system.
Finally, the particle density distribution functions for a trap containing
superfluid fermionic atoms are computed using a Thomas-Fermi approach. The one
and two channel behavior is found to be very different; we find a narrowing of
the density profile as a result of Feshbach resonance effects. Importantly, we
infer that the ratio between bosonic and fermionic scattering lengths depends
on the magnetic detuning and is generally smaller than 2. Future experiments
will be required to determine to what extent this ratio varies with magnetic
fields.; Comment: 8 pages...

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## Statistical Mechanics of Jammed Matter

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 03/03/2005

Relevância na Pesquisa

65.49%

A thermodynamic formulation of jammed matter is reviewed. Experiments and
simulations of compressed emulsions and granular materials are then used to
provide a foundation for the thermodynamics.; Comment: 51 pages, 21 figures

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## Particle dynamics and effective temperature of jammed granular matter in a slowly sheared 3D Couette cell

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

65.49%

We report experimental measurements of particle dynamics on slowly sheared
granular matter in a three-dimensional (3D) Couette cell. A closely-packed
ensemble of transparent spherical beads is confined by an external pressure and
filled with fluid to match both the density and refractive index of the beads.
This allows us to track tracer particles embedded in the system and obtain
three-dimensional trajectories as a function of time. We study the PDF of the
vertical and radial displacements, finding Gaussian and exponential
distributions, respectively. For slow shear rates, the mean-square fluctuations
in all three directions are found to be dependent only on the angular
displacement of the Couette cell. Both the diffusivity and mobility of tracer
particles are proportional to the shear rate, giving rise to a constant
effective temperature, characteristic of the jammed system.; Comment: 17 pages, 19 figures

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## Friction and dilatancy in immersed granular matter

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 10/06/2008

Relevância na Pesquisa

65.49%

The friction of a sliding plate on a thin immersed granular layer obeys
Amonton-Coulomb law. We bring to the fore a large set of experimental results
which indicate that, over a few decades of values, the effective dynamical
friction-coefficient depends neither on the viscosity of the interstitial fluid
nor on the size of beads in the sheared layer, which bears out the analogy with
the solid-solid friction in a wide range of experimental parameters. We
accurately determine the granular-layer dilatancy, which dependance on the
grain size and slider velocity can be qualitatively accounted by considering
the rheological behaviour of the whole slurry. However, additional results,
obtained after modification of the grain surface by a chemical treatment,
demonstrate that the theoretical description of the flow properties of granular
matter, even immersed, requires the detailed properties of the grain surface to
be taken into account.; Comment: 4 pages, 4 figures

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## Matter-wave interferometry in periodic and quasi-periodic arrays

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/04/2004

Relevância na Pesquisa

65.49%

We calculate within a Bose-Hubbard tight-binding model the matter-wave flow
driven by a constant force through a Bose-Einstein condensate of Rb 87 atoms in
various types of quasi-onedimensional arrays of potential wells. Interference
patterns are obtained when beam splitting is induced by creating energy
minigaps either through period doubling or through quasi-periodicity governed
by the Fibonacci series. The generation of such condensate modulations by means
of optical-laser structures is also discussed.; Comment: 11 pages, 6 figures. To appear in Opt. Comm

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## Electrostatics in soft matter

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 27/11/2008

Relevância na Pesquisa

65.49%

Recent progress in the understanding of the effect of electrostatics in soft
matter is presented. A vast amount of materials contains ions ranging from the
molecular scale (e.g., electrolyte) to the meso/macroscopic one (e.g., charged
colloidal particles or polyelectrolytes). Their (micro)structure and
physicochemical properties are especially dictated by the famous and
redoubtable long-ranged Coulomb interaction. In particular theoretical and
simulational aspects, including the experimental motivations, will be
discussed.; Comment: Topical review

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## Continuous theory of active matter systems with metric-free interactions

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/03/2012

Relevância na Pesquisa

65.49%

We derive a hydrodynamic description of metric-free active matter: starting
from self-propelled particles aligning with neighbors defined by "topological"
rules, not metric zones, -a situation advocated recently to be relevant for
bird flocks, fish schools, and crowds- we use a kinetic approach to obtain
well-controlled nonlinear field equations. We show that the density-independent
collision rate per particle characteristic of topological interactions
suppresses the linear instability of the homogeneous ordered phase and the
nonlinear density segregation generically present near threshold in metric
models, in agreement with microscopic simulations.; Comment: Submitted to Physical Review Letters

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