116 research outputs found
Modelling Processes for Flexible Packaging
The paper explains that progress in flexible packaging technology can benefit from detailed modeling of processes and/or material properties. The example of film blowing is developed in some detail in view of its simplicity. It is shown that useful information on the molecular orientation in the produced film can be obtained by using the known values of the process variables, plus the outcome of a simple experiment that can be performed while the film is being produced, without disturbing the process. Molecular orientations are important in determining the film mechanical and barrier properties. Other examples are briefly discussed
Free-space quantum key distribution by rotation-invariant twisted photons
Twisted photons are photons carrying a well-defined nonzero value of orbital
angular momentum (OAM). The associated optical wave exhibits a helical shape of
the wavefront (hence the name) and an optical vortex at the beam axis. The OAM
of light is attracting a growing interest for its potential in photonic
applications ranging from particle manipulation, microscopy and
nanotechnologies, to fundamental tests of quantum mechanics, classical data
multiplexing and quantum communication. Hitherto, however, all results obtained
with optical OAM were limited to laboratory scale. Here we report the
experimental demonstration of a link for free-space quantum communication with
OAM operating over a distance of 210 meters. Our method exploits OAM in
combination with optical polarization to encode the information in
rotation-invariant photonic states, so as to guarantee full independence of the
communication from the local reference frames of the transmitting and receiving
units. In particular, we implement quantum key distribution (QKD), a protocol
exploiting the features of quantum mechanics to guarantee unconditional
security in cryptographic communication, demonstrating error-rate performances
that are fully compatible with real-world application requirements. Our results
extend previous achievements of OAM-based quantum communication by over two
orders of magnitudes in the link scale, providing an important step forward in
achieving the vision of a worldwide quantum network
Wall slip in primitive chain network simulations of shear startup of entangled polymers and its effect on the shear stress undershoot
In some recent experiments on entangled polymers of stress growth in startup
of fast shear flows an undershoot in the shear stress is observed following the
overshoot, i.e., before approaching the steady state. Whereas tumbling of the
entangled chain was proposed to be at its origin, here we investigate another
possible cause for the stress undershoot, i.e., slippage at the interface
between polymer and solid wall. To this end, we extend the primitive chain
network model to include slip at the interface between entangled polymeric
liquids and solid walls with grafted polymers. We determine the slip velocity
at the wall, and the shear rate in the bulk, by imposing that the shear stress
in the bulk polymers is equal to that resulting from the polymers grafted at
the wall. After confirming that the predicted results for the steady state are
reasonable, we examine the transient behavior. The simulations confirm that
slippage weakens the magnitude of the stress overshoot, as reported earlier.
The undershoot is also weakened, or even disappears, because of a reduced
coherence in molecular tumbling. In other words, the disentanglement between
grafted and bulk chains, occurring throughout the stress overshoot region, does
not contribute to the stress undershoot.Comment: 38 pages and 9 figure
Mechanical Properties of End-crosslinked Entangled Polymer Networks using Sliplink Brownian Dynamics Simulations
The mechanical properties of a polymeric network containing both crosslinks
and sliplinks (entanglements) are studied using a multi-chain Brownian dynamics
simulation. We coarse-grain at the level of chain segments connecting
consecutive nodes (cross- or sliplinks), with particular attention to the
Gaussian statistics of the network. Affine displacement of nodes is not
imposed: their displacement as well as sliding of monomers through sliplinks is
governed by force balances. The simulation results of stress in uniaxial
extension and the full stress tensor in simple shear including the (non-zero)
second normal stress difference are presented for monodisperse chains with up
to 18 entanglements between two crosslinks. The cases of two different force
laws of the subchains (Gaussian chains and chains with finite extensibility)
for two different numbers of monomers in a subchain (no = 50 and no = 100) are
examined. It is shown that the additivity assumption of slip- and crosslink
contribution holds for sufficiently long chains with two or more entanglements,
and that it can be used to construct the strain response of a network of
infinitely long chains. An important consequence is that the contribution of
sliplinks to the small-strain shear modulus is about ⅔ of the
contribution of a crosslink
Generation of an induced pluripotent stem cell line (UCSCi002-A) from a patient with a variant in TARDBP gene associated with familial amyotrophic lateral sclerosis and frontotemporal dementia
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively affects motor neurons. In 20% of cases, ALS appears in comorbidity with frontotemporal dementia (FTD). We generated patient-derived-induced Pluripotent Stem Cells (iPSCs), from an ALS/FTD patient. The patient had a familial form of the disease and a missense variant in TARDBP gene. We used an established protocol based on Sendai virus to reprogram fibroblasts. We confirmed the stemness and the pluripotency of the iPSC clones, thus generating embryoid bodies. We believe that the iPSC line carrying a TARDBP mutation could be a valuable tool to investigate TDP-43 proteinopathy linked to ALS
First observation of the quantized exciton-polariton field and effect of interactions on a single polariton.
© 2018 The Authors. Published by Science. This is an open access article available under a Creative Commons licence.
The published version can be accessed at the following link on the publisherâs website: https://doi.org/10.1126/sciadv.aao6814Polaritons are quasi-particles that originate from the coupling of light with matter and that demonstrate quantum phenomena at the many-particle mesoscopic level, such as Bose-Einstein condensation and superfluidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behavior has remained fully accounted for by classical and mean-field theories. We report the first experimental demonstration of a genuinely quantum state of the microcavity polariton field, by swapping a photon for a polariton in a two-photon entangled state generated by parametric downconversion. When bringing this single-polariton quantum state in contact with a polariton condensate, we observe a disentangling with the external photon. This manifestation of a polariton quantum state involving a single quantum unlocks new possibilities for quantum information processing with interacting bosons
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