185 research outputs found
Cell therapies for pancreatic beta-cell replenishment.
The current treatment approach for type 1 diabetes is based on daily insulin injections, combined with blood glucose monitoring. However, administration of exogenous insulin fails to mimic the physiological activity of the islet, therefore diabetes often progresses with the development of serious complications such as kidney failure, retinopathy and vascular disease. Whole pancreas transplantation is associated with risks of major invasive surgery along with side effects of immunosuppressive therapy to avoid organ rejection. Replacement of pancreatic beta-cells would represent an ideal treatment that could overcome the above mentioned therapeutic hurdles. In this context, transplantation of islets of Langerhans is considered a less invasive procedure although long-term outcomes showed that only 10 % of the patients remained insulin independent five years after the transplant. Moreover, due to shortage of organs and the inability of islet to be expanded ex vivo, this therapy can be offered to a very limited number of patients. Over the past decade, cellular therapies have emerged as the new frontier of treatment of several diseases. Furthermore the advent of stem cells as renewable source of cell-substitutes to replenish the beta cell population, has blurred the hype on islet transplantation. Breakthrough cellular approaches aim to generate stem-cell-derived insulin producing cells, which could make diabetes cellular therapy available to millions. However, to date, stem cell therapy for diabetes is still in its early experimental stages. This review describes the most reliable sources of stem cells that have been developed to produce insulin and their most relevant experimental applications for the cure of diabetes
Room temperature Bloch surface wave polaritons
Polaritons are hybrid light-matter quasi-particles that have gathered a
significant attention for their capability to show room temperature and
out-of-equilibrium Bose-Einstein condensation. More recently, a novel class of
ultrafast optical devices have been realized by using flows of polariton
fluids, such as switches, interferometers and logical gates. However, polariton
lifetimes and propagation distance are strongly limited by photon losses and
accessible in-plane momenta in usual microcavity samples. In this work, we show
experimental evidence of the formation of room temperature propagating
polariton states arising from the strong coupling between organic excitons and
a Bloch surface wave. This result, which was only recently predicted, paves the
way for the realization of polariton devices that could allow lossless
propagation up to macroscopic distances
Ultrafast flow of interacting organic polaritons
The strong-coupling of an excitonic transition with an electromagnetic mode
results in composite quasi-particles called exciton-polaritons, which have been
shown to combine the best properties of their bare components in semiconductor
microcavities. However, the physics and applications of polariton flows in
organic materials and at room temperature are still unexplored because of the
poor photon confinement in such structures. Here we demonstrate that polaritons
formed by the hybridization of organic excitons with a Bloch Surface Wave are
able to propagate for hundreds of microns showing remarkable third-order
nonlinear interactions upon high injection density. These findings pave the way
for the studies of organic nonlinear light-matter fluxes and for a
technological promising route of dissipation-less on-chip polariton devices
working at room temperature.Comment: Improved version with polariton-polariton interactions. 13 pages, 4
figures, supporting 6 pages, 6 figure
Full-Bloch beams and ultrafast Rabi-rotating vortices
Strongly-coupled quantum fields, such as multi-component atomic condensates,
optical fields and polaritons, are remarkable systems where the simple dynamics
of coupled oscillators can meet the intricate phenomenology of quantum fluids.
When the coupling between the components is coherent, not only the particles
number, but also their phase texture that maps the linear and angular momentum,
can be exchanged. Here, on a system of exciton-polaritons, we have realized a
so-called full-Bloch beam: a configuration in which all superpositions of the
upper and the lower polariton -- all quantum states of the associated Hilbert
space -- are simultaneously present at different points of the physical space,
evolving in time according to Rabi-oscillatory dynamics. As a result, the light
emitted by the cavity displays a peculiar dynamics of spiraling vortices
endowed with oscillating linear and angular momentum and exhibiting ultrafast
motion of their cores with striking accelerations to arbitrary speeds. This
remarkable vortex motion is shown to result from distortions of the
trajectories by a homeomorphic mapping between the Rabi rotation of the full
wavefunction on the Bloch sphere and Apollonian circles in the real space where
the observation is made. Such full-Bloch beams offer new prospects at a
fundamental level regarding their topological properties or in the
interpretation of quantum mechanics, and the Rabi-rotating vortices they yield
should lead to interesting applications such as ultrafast optical tweezers.Comment: Published version, 18 pages, 8 figures, 4 ancillary movie
The sternum reconstruction: Present and future perspectives
Sternectomy is a procedure mainly used for removing tumor masses infiltrating
the sternum or treating infections. Moreover, the removal of the sternum
involves the additional challenge of performing a functional reconstruction.
Fortunately, various approaches have been proposed for improving the
operation and outcome of reconstruction, including allograft transplantation,
using novel materials, and developing innovative surgical approaches, which
promise to enhance the quality of life for the patient. This review will highlight
the surgical approaches to sternum reconstruction and the new perspectives in
the current literature
Topologically driven Rabi-oscillating interference dislocation
Quantum vortices are the quantized version of classical vortices. Their
center is a phase singularity or vortex core around which the flow of particles
as a whole circulates and is typical in superfluids, condensates and optical
fields. However, the exploration of the motion of the phase singularities in
coherently-coupled systems is still underway. We theoretically analyze the
propagation of an interference dislocation in the regime of strong coupling
between light and matter, with strong mass imbalance, corresponding to the case
of microcavity exciton-polaritons. To this end, we utilize combinations of
vortex and tightly focused Gaussian beams, which are introduced through
resonant pulsed pumping. We show that a dislocation originates from
self-interference fringes, due to the non-parabolic dispersion of polaritons
combined with moving Rabi-oscillating vortices. The morphology of singularities
is analyzed in the Poincar\'{e} space for the pseudospin associated to the
polariton states. The resulting beam carries orbital angular momentum with
decaying oscillations due to the loss of overlap between the normal modes of
the polariton system.Comment: 9 pages, 6 figure
Interactions and scattering of quantum vortices in a polariton fluid
Quantum vortices, the quantized version of classical vortices, play a
prominent role in superfluid and superconductor phase transitions. However,
their exploration at a particle level in open quantum systems has gained
considerable attention only recently. Here we study vortex pair interactions in
a resonant polariton fluid created in a solid-state microcavity. By tracking
the vortices on picosecond time scales, we reveal the role of nonlinearity, as
well as of density and phase gradients, in driving their rotational dynamics.
Such effects are also responsible for the split of composite spin-vortex
molecules into elementary half-vortices, when seeding opposite vorticity
between the two spinorial components. Remarkably, we also observe that vortices
placed in close proximity experience a pull-push scenario leading to unusual
scattering-like events that can be described by a tunable effective potential.
Understanding vortex interactions can be useful in quantum hydrodynamics and in
the development of vortex-based lattices, gyroscopes, and logic devices.Comment: 12 pages, 7 figures, Supplementary Material and 5 movies included in
arXi
- …