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Publications

Small-scale anisotropy in turbulent boundary layers

Cornell Affiliated Author(s)
Author
A. Pumir
H. Xu
E.D. Siggia
Abstract

In a channel flow, the velocity fluctuations are inhomogeneous and anisotropic. Yet, the small-scale properties of the flow are expected to behave in an isotropic manner in the very-large-Reynolds-number limit. We consider the statistical properties of small-scale velocity fluctuations in a turbulent channel flow at moderately high Reynolds number , using the Johns Hopkins University Turbulence Database.

Journal
Journal of Fluid Mechanics
Date Published
Research Area

Human talar and femoral cartilage have distinct mechanical properties near the articular surface

Cornell Affiliated Author(s)
Author
C.R. Henak
K.A. Ross
E.D. Bonnevie
L.A. Fortier
Itai Cohen
J.G. Kennedy
L.J. Bonassar
Abstract

Talar osteochondral lesions (OCL) frequently occur following injury. Surgical interventions such as femoral condyle allogeneic or autogenic osteochondral transplant (AOT) are often used to treat large talar OCL. Although AOT aims to achieve OCL repair by replacing damaged cartilage with mechanically matched cartilage, the spatially inhomogeneous material behavior of the talar dome and femoral donor sites have not been evaluated or compared.

Journal
Journal of Biomechanics
Date Published
Funding Source
11-582
CMMI 1536463
1R21-AR062677
Research Area
Group (Lab)
Itai Cohen Group

Imaging chiral symmetry breaking from Kekulé bond order in graphene

Cornell Affiliated Author(s)
Author
Christopher Gutiérrez
C.-J. Kim
L. Brown
T. Schiros
D. Nordlund
E.B. Lochocki
K.M. Shen
J. Park
A.N. Pasupathy
Abstract

Chirality - or handedness' - is a symmetry property crucial to fields as diverse as biology, chemistry and high-energy physics. In graphene, chiral symmetry emerges naturally as a consequence of the carbon honeycomb lattice. This symmetry can be broken by interactions that couple electrons with opposite momenta in graphene. Here we directly visualize the formation of Kekulé bond order, one such phase of broken chiral symmetry, in an ultraflat graphene sheet grown epitaxially on a copper substrate.

Journal
Nature Physics
Date Published
Funding Source
N00014-14-1-0501
FA9550-11-1-0010
DMR-1120296
FA2386-13-1-4118
FA9550-11-1-0033
N00014-12-1-0791
DMR-1420634
2012M3A7B4049887
Group (Lab)
Kyle Shen Group

Origin of the multiple configurations that drive the response of δ-plutonium's elastic moduli to temperature

Cornell Affiliated Author(s)
Author
A. Migliori
Per Söderlind
A. Landa
F.J. Freibert
B. Maiorov
B.J. Ramshaw
Jon Betts
Abstract

The electronic and thermodynamic complexity of plutonium has resisted a fundamental understanding for this important elemental metal. A critical test of any theory is the unusual softening of the bulk modulus with increasing temperature, a result that is counterintuitive because no or very little change in the atomic volume is observed upon heating. This unexpected behavior has in the past been attributed to competing but never-observed electronic states with different bonding properties similar to the scenario with magnetic states in Invar alloys.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Funding Source
DE-SC0001089
DE-AC52-07NA27344
Group (Lab)
Brad Ramshaw Group

Electron Doping of the Parent Cuprate La2CuO4 without Cation Substitution

Cornell Affiliated Author(s)
Author
H.I. Wei
C. Adamo
E.A. Nowadnick
E.B. Lochocki
S. Chatterjee
J.P. Ruf
M.R. Beasley
D.G. Schlom
K.M. Shen
Abstract

In the cuprates, carrier doping of the Mott insulating parent state is necessary to realize superconductivity as well as a number of other exotic states involving charge or spin density waves. Cation substitution is the primary method for doping carriers into these compounds, and is the only known method for electron doping in these materials. Here, we report electron doping without cation substitution in epitaxially stabilized thin films of La2CuO4 grown via molecular-beam epitaxy.

Journal
Physical Review Letters
Date Published
Group (Lab)
Kyle Shen Group

Lattice bosons with infinite-range checkerboard interactions

Cornell Affiliated Author(s)
Author
B. Sundar
E.J. Mueller
Abstract

Motivated by experiments performed by Landig et al. [Nature (London) 532, 476 (2016)NATUAS0028-083610.1038/nature17409], we consider a two-dimensional Bose gas in an optical lattice, trapped inside a single mode superradiant Fabry-Perot cavity. The cavity mediates infinite-range checkerboard interactions between the atoms, which produces competition between Mott insulator, charge-density wave, superfluid, and supersolid phases. We calculate the phase diagram of this Bose gas in a homogeneous system and in the presence of a harmonic trap. © 2016 American Physical Society.

Journal
Physical Review A
Date Published
Funding Source
1508300
PHY-1508300

Observation of a new superfluid phase for 3He embedded in nematically ordered aerogel

Cornell Affiliated Author(s)
Author
N. Zhelev
M. Reichl
T.S. Abhilash
E.N. Smith
K.X. Nguyen
E.J. Mueller
J.M. Parpia
Abstract

In bulk superfluid 3He at zero magnetic field, two phases emerge with the B-phase stable everywhere except at high pressures and temperatures, where the A-phase is favoured. Aerogels with nanostructure smaller than the superfluid coherence length are the only means to introduce disorder into the superfluid. Here we use a torsion pendulum to study 3He confined in an extremely anisotropic, nematically ordered aerogel consisting of ∼410 nm-thick alumina strands, spaced by ∼100 nm, and aligned parallel to the pendulum axis.

Journal
Nature Communications
Date Published
Funding Source
DMR 1202991
PHY 1508300
Group (Lab)
Jeevak Parpia Group

Tunable shear thickening in suspensions

Cornell Affiliated Author(s)
Author
N.Y.C. Lin
C. Ness
M.E. Cates
J. Sun
Itai Cohen
Abstract

Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomenon in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allows for tuning of flow properties during shear itself.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Funding Source
1232666
1509308
EP/N025318/1
DMR-1120296
EP/J007404
Group (Lab)
Itai Cohen Group

All-optical vector measurement of spin-orbit-induced torques using both polar and quadratic magneto-optic Kerr effects

Cornell Affiliated Author(s)
Author
Xin Fan
Alex Mellnik
Wenrui Wang
Neal Reynolds
Tao Wang
Halise Celik
Virginia Lorenz
Daniel Ralph
John Xiao
Abstract

We demonstrate that the magneto-optic-Kerr effect with normal light incidence can be used to obtain quantitative optical measurements of both components of spin-orbit-induced torque (both the antidamping and effective-field components) in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the quadratic Kerr effect as well as the polar Kerr effect. The two effects can be distinguished by properly selecting the polarization of the incident light.

Journal
AIP Publishing
Date Published
Funding Source
DMR-1120296
DMR-1505192
DMR-1010768
ECCS-0335765
N66001-11-1-4110

The Chd1 chromatin remodeler can sense both entry and exit sides of the nucleosome

Cornell Affiliated Author(s)
Author
I.M. Nodelman
K.C. Horvath
R.F. Levendosky
J. Winger
R. Ren
A. Patel
M. Li
M.D. Wang
E. Roberts
G.D. Bowman
Abstract

Chromatin remodelers are essential for establishing and maintaining the placement of nucleosomes along genomic DNA. Yet how chromatin remodelers recognize and respond to distinct chromatin environments surrounding nucleosomes is poorly understood. Here, we use Lac repressor as a tool to probe how a DNA-bound factor influences action of the Chd1 remodeler. We show that Chd1 preferentially shifts nucleosomes away from Lac repressor, demonstrating that a DNA-bound factor defines a barrier for nucleosome positioning.

Journal
Nucleic Acids Research
Date Published
Research Area
Group (Lab)
Michelle Wang Group