4,320 research outputs found
Periodisme cientĂfic i relacions pĂşbliques
Les empreses farmacèutiques, laboratoris, centres d'investigació, editorials, fundacions
hospitalà ries, autors, experts i investigadors, universitats i centres tecnològics tenen
l'obligació d'executar amb professionalitat les tècniques i procediments de relació
amb els mitjans de comunicaciĂł. Si pretenen arribar a l'opiniĂł pĂşblica, si pretenen difondre
coneixement més enllà de les seves fronteres internes, han de treballar a través
dels professionals experts que els poden oferir el seu coneixement, la seva experiència
i la seva agenda de mitjans. No Ă©s suficient amb l'ediciĂł d'un descobriment o un treball
d'investigació en un format digne, trucar als periodistes i esperar que vinguin. És necessari
crear un interès en els professionals de la comunicació perquè aquesta informació
s'entengui com a «oportuna» i «inèdita», per damunt de centenars d'altres informacions
que tenen entre mans. I la ciència no n'és una excepció. Hi ha molt material que pot i
vol convertir-se en fet noticiable. Les dificultats de fer bon periodisme cientĂfic sĂłn,
doncs, evidents. Les tècniques de relacions públiques «ben fetes» poden facilitar el treball
dels periodistes en el complex context del periodisme cientĂfic.The pharmaceutical companies, laboratories, investigation centers, publishing houses,
hospital foundations, authors, experts and researchers, universities and technological
centers must carry out with professionalism techniques and methods of the relationship
with the media. If they seek to arrive to the public opinion, if they seek to
diffuse knowledge beyond their internal frontiers, they should work through the expert
professionals who can provide them their knowledge, experience and agenda-setting. It is not enough publicizing a discovery or an investigation in a worthy format, calling to the
journalists and waiting for them. It is necessary to create an interest among the communication
professionals so that information is understood as «opportune» and «unpublished».
And science is not an exception. Journalists have much science material that they can
transform into a piece of news. The problems to do a good scientific journalism are evident.
«Well made» techniques of public relations can facilitate the journalists work
in the complex context of scientific journalism
Localized and extended states in a disordered trap
We study Anderson localization in a disordered potential combined with an
inhomogeneous trap. We show that the spectrum displays both localized and
extended states, which coexist at intermediate energies. In the region of
coexistence, we find that the extended states result from confinement by the
trap and are weakly affected by the disorder. Conversely, the localized states
correspond to eigenstates of the disordered potential, which are only affected
by the trap via an inhomogeneous energy shift. These results are relevant to
disordered quantum gases and we propose a realistic scheme to observe the
coexistence of localized and extended states in these systems.Comment: Published versio
Localization from quantum interference in one-dimensional disordered potentials
We show that the tails of the asymptotic density distribution of a quantum
wave packet that localizes in the the presence of random or quasiperiodic
disorder can be described by the diagonal term of the projection over the
eingenstates of the disordered potential. This is equivalent of assuming a
phase randomization of the off-diagonal/interference terms. We demonstrate
these results through numerical calculations of the dynamics of ultracold atoms
in the one-dimensional speckle and quasiperiodic potentials used in the recent
experiments that lead to the observation of Anderson localization for matter
waves [Billy et al., Nature 453, 891 (2008); Roati et al., Nature 453, 895
(2008)]. For the quasiperiodic case, we also discuss the implications of using
continuos or discrete models.Comment: 5 pages, 3 figures; minor changes, references update
Anderson localization of matter waves in tailored disordered potentials
We show that, in contrast to immediate intuition, Anderson localization of
noninteracting particles induced by a disordered potential in free space can
increase (i.e., the localization length can decrease) when the particle energy
increases, for appropriately tailored disorder correlations. We predict the
effect in one, two, and three dimensions, and propose a simple method to
observe it using ultracold atoms placed in optical disorder. The increase of
localization with the particle energy can serve to discriminate quantum versus
classical localization
Smoothing effect and delocalization of interacting Bose-Einstein condensates in random potentials
We theoretically investigate the physics of interacting Bose-Einstein
condensates at equilibrium in a weak (possibly random) potential. We develop a
perturbation approach to derive the condensate wavefunction for an amplitude of
the potential smaller than the chemical potential of the condensate and for an
arbitrary spatial variation scale of the potential. Applying this theory to
disordered potentials, we find in particular that, if the healing length is
smaller than the correlation length of the disorder, the condensate assumes a
delocalized Thomas-Fermi profile. In the opposite situation where the
correlation length is smaller than the healing length, we show that the random
potential can be significantly smoothed and, in the meanfield regime, the
condensate wavefunction can remain delocalized, even for very small correlation
lengths of the disorder.Comment: The word "screening" has been changed to "smoothing" to avoid
confusions with other effects discussed in the literature. This does not
affect the content of paper, nor the results, nor the physical discussio
Localization of a matter wave packet in a disordered potential
We theoretically study the Anderson localization of a matter wave packet in a
one-dimensional disordered potential. We develop an analytical model which
includes the initial phase-space density of the matter wave and the spectral
broadening induced by the disorder. Our approach predicts a behavior of the
localized density profile significantly more complex than a simple exponential
decay. These results are confirmed by large-scale and long-time numerical
calculations. They shed new light on recent experiments with ultracold atoms
and may impact their analysis
Experimental study of the transport of coherent interacting matter-waves in a 1D random potential induced by laser speckle
We present a detailed analysis of the 1D expansion of a coherent interacting
matterwave (a Bose-Einstein condensate) in the presence of disorder. A 1D
random potential is created via laser speckle patterns. It is carefully
calibrated and the self-averaging properties of our experimental system are
discussed. We observe the suppression of the transport of the BEC in the random
potential. We discuss the scenario of disorder-induced trapping taking into
account the radial extension in our experimental 3D BEC and we compare our
experimental results with the theoretical predictions
Brillouin propagation modes in optical lattices: Interpretation in terms of nonconventional stochastic resonance
We report the first direct observation of Brillouin-like propagation modes in a dissipative periodic optical lattice. This has been done by observing a resonant behavior of the spatial diffusion coefficient in the direction corresponding to the propagation mode with the phase velocity of the moving intensity modulation used to excite these propagation modes. Furthermore, we show theoretically that the amplitude of the Brillouin mode is a nonmonotonic function of the strength of the noise corresponding to the optical pumping, and discuss this behavior in terms of nonconventional stochastic resonance
Anderson Localization of Bogolyubov Quasiparticles in Interacting Bose-Einstein Condensates
We study the Anderson localization of Bogolyubov quasiparticles in an
interacting Bose-Einstein condensate (with healing length \xi) subjected to a
random potential (with finite correlation length \sigma_R). We derive
analytically the Lyapunov exponent as a function of the quasiparticle momentum
k and we study the localization maximum k_{max}. For 1D speckle potentials, we
find that k_{max} is proportional to 1/\xi when \xi is much larger than
\sigma_R while k_{max} is proportional to 1/\sigma_R when \xi is much smaller
than \sigma_R, and that the localization is strongest when \xi is of the order
of \sigma_R. Numerical calculations support our analysis and our estimates
indicate that the localization of the Bogolyubov quasiparticles is accessible
in current experiments with ultracold atoms.Comment: published version (no significant changes compared to last version
Effective tumor immunotherapy: start the engine, release the brakes, step on the gas pedal,...and get ready to face autoimmunity
Cellular immune responses can destroy cancer cells, achieving the cure of experimental malignancies. An expanding wealth of knowledge on the molecular basis of how to prime and amplify a T cell response has fueled a number of strategies successful at treating established tumors (rather than merely preventing tumor grafting). The most efficacious approaches operate at different stages, including: 1) priming the immune response using tumor antigen-expressing dendritic cells or tumor cells transfected with genes that render them immunogenic, 2) sustaining and amplifying immunity using agonistic monoclonal antibodies against costimulatory molecules or immune-potentiating cytokines, and 3) eliminating mechanisms that self-regulate the strength of the immune response, such as inhibitory receptors or regulatory T cells. A rational combination of such approaches holds great hope for cumulative and synergistic effects, but there is also evidence that they can open the flood-gates for unwanted inflammatory reactions. The next decade can be envisioned as the time when the first reproducibly efficacious combination regimes for cancer immunotherapy will become available and widely used in the clinic, as clinicians learn the best strategies and try to harness their potentially damaging effects
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