42 research outputs found
Invariance of Structure in an Aging Colloidal Glass
We study concentrated colloidal suspensions, a model system which has a glass
transition. The non-equilibrium nature of the glassy state is most clearly
highlighted by aging -- the dependence of the system's properties on the time
elapsed since vitrification. Fast laser scanning confocal microscopy allows us
to image a colloidal glass and track the particles in three dimensions. We
analyze the static structure in terms of tetrahedral packing. We find that
while the aging of the suspension clearly affects its dynamics, none of the
geometrical quantities associated with tetrahedra change with age.Comment: Submitted to the proceedings of "The 3rd International Workshop on
Complex Systems" in Sendai, Japa
Towards Large-Scale Quantum Networks
The vision of a quantum internet is to fundamentally enhance Internet
technology by enabling quantum communication between any two points on Earth.
While the first realisations of small scale quantum networks are expected in
the near future, scaling such networks presents immense challenges to physics,
computer science and engineering. Here, we provide a gentle introduction to
quantum networking targeted at computer scientists, and survey the state of the
art. We proceed to discuss key challenges for computer science in order to make
such networks a reality.Comment: To be presented at the Sixth Annual ACM International Conference on
Nanoscale Computing and Communication, Dublin, Irelan
Correlations of Structure and Dynamics in an Aging Colloidal Glass
We study concentrated colloidal suspensions, a model system which has a glass
transition. Samples in the glassy state show aging, in that the motion of the
colloidal particles slows as the sample ages from an initial state. We study
the relationship between the static structure and the slowing dynamics, using
confocal microscopy to follow the three-dimensional motion of the particles.
The structure is quantified by considering tetrahedra formed by quadruplets of
neighboring particles. We find that while the sample clearly slows down during
aging, the static properties as measured by tetrahedral quantities do not vary.
However, a weak correlation between tetrahedron shape and mobility is observed,
suggesting that the structure facilitates the motion responsible for the sample
aging.Comment: Submitted to Solid State Communication
Direct visualization of aging in colloidal glasses
We use confocal microscopy to directly visualize the dynamics of aging
colloidal glasses. We prepare a colloidal suspension at high density, a simple
model system which shares many properties with other glasses, and initiate
experiments by stirring the sample. We follow the motion of several thousand
colloidal particles after the stirring and observe that their motion
significantly slows as the sample ages. The aging is both spatially and
temporally heterogeneous. Furthermore, while the characteristic relaxation time
scale grows with the age of the sample, nontrivial particle motions continue to
occur on all time scales.Comment: submitted to proceedings for Liquid Matter Conference 200
Designing a Quantum Network Protocol
The second quantum revolution brings with it the promise of a quantum
internet. As the first quantum network hardware prototypes near completion new
challenges emerge. A functional network is more than just the physical
hardware, yet work on scalable quantum network systems is in its infancy. In
this paper we present a quantum network protocol designed to enable end-to-end
quantum communication in the face of the new fundamental and technical
challenges brought by quantum mechanics. We develop a quantum data plane
protocol that enables end-to-end quantum communication and can serve as a
building block for more complex services. One of the key challenges in
near-term quantum technology is decoherence -- the gradual decay of quantum
information -- which imposes extremely stringent limits on storage times. Our
protocol is designed to be efficient in the face of short quantum memory
lifetimes. We demonstrate this using a simulator for quantum networks and show
that the protocol is able to deliver its service even in the face of
significant losses due to decoherence. Finally, we conclude by showing that the
protocol remains functional on the extremely resource limited hardware that is
being developed today underlining the timeliness of this work
Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures
Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo