421 research outputs found
Ketogenic Diet in the Treatment of Gliomas and Glioblastomas
In recent years, scientific interest in the use of the ketogenic diet (KD) as a complementary approach to the standard cancer therapy has grown, in particular against those of the central nervous system (CNS). In metabolic terms, there are the following differences between healthy and neoplastic cells: neoplastic cells divert their metabolism to anaerobic glycolysis (Warburg effect), they alter the normal mitochondrial functioning, and they use mainly certain amino acids for their own metabolic needs, to gain an advantage over healthy cells and to lead to a pro-oncogenetic effect. Several works in literature speculate which are the molecular targets of KD used against cancer. The following different mechanisms of action will be explored in this review: metabolic, inflammatory, oncogenic and oncosuppressive, ROS, and epigenetic modulation. Preclinical and clinical studies on the use of KD in CNS tumors have also increased in recent years. An interesting hypothesis emerged from the studies about the possible use of a ketogenic diet as a combination therapy along with chemotherapy (CT) and radiotherapy (RT) for the treatment of cancer. Currently, however, clinical data are still very limited but encouraging, so we need further studies to definitively validate or disprove the role of KD in fighting against cancer
Ultrafast control of Rabi oscillations in a polariton condensate
We report the experimental observation and control of space and time-resolved
light-matter Rabi oscillations in a microcavity. Our setup precision and the
system coherence are so high that coherent control can be implemented with
amplification or switching off of the oscillations and even erasing of the
polariton density by optical pulses. The data is reproduced by a fundamental
quantum optical model with excellent accuracy, providing new insights on the
key components that rule the polariton dynamics.Comment: 5 pages, 3 figures, supplementary 7 pages, 4 figures. Supplementary
videos:
https://drive.google.com/folderview?id=0B0QCllnLqdyBNjlMLTdjZlNhbTQ&usp=sharin
Vortex and half-vortex dynamics in a spinor quantum fluid of interacting polaritons
Spinorial or multi-component Bose-Einstein condensates may sustain fractional
quanta of circulation, vorticant topological excitations with half integer
windings of phase and polarization. Matter-light quantum fluids, such as
microcavity polaritons, represent a unique test bed for realising strongly
interacting and out-of-equilibrium condensates. The direct access to the phase
of their wavefunction enables us to pursue the quest of whether half vortices
---rather than full integer vortices--- are the fundamental topological
excitations of a spinor polariton fluid. Here, we are able to directly generate
by resonant pulsed excitations, a polariton fluid carrying either the half or
full vortex states as initial condition, and to follow their coherent evolution
using ultrafast holography. Surprisingly we observe a rich phenomenology that
shows a stable evolution of a phase singularity in a single component as well
as in the full vortex state, spiraling, splitting and branching of the initial
cores under different regimes and the proliferation of many vortex anti-vortex
pairs in self generated circular ripples. This allows us to devise the
interplay of nonlinearity and sample disorder in shaping the fluid and driving
the phase singularities dynamicsComment: New version complete with revised modelization, discussion and added
material. 8 pages, 7 figures. Supplementary videos:
https://drive.google.com/folderview?id=0B0QCllnLqdyBfmc2ai0yVF9fa2g2VnZodGUwemVkLThBb3BoOVRKRDJMS2dUdjlZdkRTQk
The colored Hanbury Brown--Twiss effect
The Hanbury Brown--Twiss effect is one of the celebrated phenomenologies of
modern physics that accommodates equally well classical (interferences of
waves) and quantum (correlations between indistinguishable particles)
interpretations. The effect was discovered in the late thirties with a basic
observation of Hanbury Brown that radio-pulses from two distinct antennas
generate signals on the oscilloscope that wiggle similarly to the naked eye.
When Hanbury Brown and his mathematician colleague Twiss took the obvious step
to propose bringing the effect in the optical range, they met with considerable
opposition as single-photon interferences were deemed impossible. The Hanbury
Brown--Twiss effect is nowadays universally accepted and, being so fundamental,
embodies many subtleties of our understanding of the wave/particle dual nature
of light. Thanks to a novel experimental technique, we report here a
generalized version of the Hanbury Brown--Twiss effect to include the frequency
of the detected light, or, from the particle point of view, the energy of the
detected photons. In addition to the known tendencies of indistinguishable
photons to arrive together on the detector, we find that photons of different
colors present the opposite characteristic of avoiding each others. We
postulate that fermions can be similarly brought to exhibit positive
(boson-like) correlations by frequency filtering.Comment: 18 pages, includes supplementary material of the derivation
Electrically controlled waveguide polariton laser
Exciton-polaritons are mixed light-matter particles offering a versatile
solid state platform to study many-body physical effects. In this work we
demonstrate an electrically controlled polariton laser, in a compact,
easy-to-fabricate and integrable configuration, based on a semiconductor
waveguide. Interestingly, we show that polariton lasing can be achieved in a
system without a global minimum in the polariton energy-momentum dispersion.
The surface cavity modes for the laser emission are obtained by adding couples
of specifically designed diffraction gratings on top of the planar waveguide,
forming an in-plane Fabry-Perot cavity. It is thanks to the waveguide geometry,
that we can apply a transverse electric field in order to finely tune the laser
energy and quality factor of the cavity modes. Remarkably, we exploit the
system sensitivity to the applied electric field to achieve an electrically
controlled population of coherent polaritons. The precise control that can be
reached with the manipulation of the grating properties and of the electric
field provides strong advantages to this device in terms of miniaturization and
integrability, two main features for the future development of coherent sources
from polaritonic technologies.Comment: 11 pages, 5 figures. Supplementary: 6 pages, 7 figure
Oxidative stress and multi-organel damage induced by two novel phytocannabinoids, cbdb and cbdp, in breast cancer cells
Over the last few years, much attention has been paid to phytocannabinoids derived from Cannabis for their therapeutic potential. ∆9-tetrahydrocannabinol (∆9-THC) and cannabidiol (CBD) are the most abundant compounds of the Cannabis sativa L. plant. Recently, novel phytocannabinoids, such as cannabidibutol (CBDB) and cannabidiphorol (CBDP), have been discovered. These new molecules exhibit the same terpenophenolic core of CBD and differ only for the length of the alkyl side chain. Roles of CBD homologs in physiological and pathological processes are emerging but the exact molecular mechanisms remain to be fully elucidated. Here, we investigated the biological effects of the newly discovered CBDB or CBDP, compared to the well-known natural and synthetic CBD (nat CBD and syn CBD) in human breast carcinoma cells that express CB receptors. In detail, our data demonstrated that the treatment of cells with the novel phytocannabinoids affects cell viability, increases the production of reactive oxygen species (ROS) and activates cellular pathways related to ROS signaling, as already demonstrated for natural CBD. Moreover, we observed that the biological activity is significantly increased upon combining CBD homologs with drugs that inhibit the activity of enzymes involved in the metabolism of endocannabinoids, such as the monoacylglycerol lipase (MAGL) inhibitor, or with drugs that induces the activation of cellular stress pathways, such as the phorbol ester 12-myristate 13-acetate (PMA)
Multicomponent polariton superfluidity in the optical parametric oscillator regime
Superfluidity, the ability of a liquid or gas to flow with zero viscosity, is one of the most remarkable
implications of collective quantum coherence. In equilibrium systems like liquid 4He and ultracold
atomic gases, superfluid behaviour conjugates diverse yet related phenomena, such as persistency
of metastable flow in multiply connected geometries and the existence of a critical velocity for
frictionless flow when hitting a static defect. The link between these different aspects of superfluid
behaviour is far less clear in driven-dissipative systems displaying collective coherence, such as
microcavity polaritons, which raises important questions about their concurrency. With a joint
theoretical and experimental study, we show that the scenario is particularly rich for polaritons
driven in a three-fluid collective coherent regime so-called optical parametric oscillator. On the one
hand, the spontaneous macroscopic coherence following the phase locking of the signal and idler
fluids has been shown to be responsible for their simultaneous quantized flow metastability. On the
other hand, we show here that pump, signal and idler have distinct responses when hitting a static
defect; while the signal displays hardly appreciable modulations, the ones appearing in pump and
idler are determined by their mutual coupling due to nonlinear and parametric processes
- …