332 research outputs found
Optical sectioning in induced coherence tomography with frequency-entangled photons
We demonstrate a different scheme to perform optical sectioning of a sample
based on the concept of induced coherence [Zou et al., Phys. Rev. Lett. 67, 318
(1991)]. This can be viewed as a different type of optical coherence tomography
scheme where the varying reflectivity of the sample along the direction of
propagation of an optical beam translates into changes of the degree of
first-order coherence between two beams. As a practical advantage the scheme
allows probing the sample with one wavelength and measuring photons with
another wavelength. In a bio-imaging scenario, this would result in a deeper
penetration into the sample because of probing with longer wavelengths, while
still using the optimum wavelength for detection. The scheme proposed here
could achieve submicron axial resolution by making use of nonlinear parametric
sources with broad spectral bandwidth emission.Comment: Published version. 11 pages, 9 figure
Coherent delocalization: Views of entanglement in different scenarios
The concept of entanglement was originally introduced to explain correlations
existing between two spatially separated systems, that cannot be described
using classical ideas. Interestingly, in recent years, it has been shown that
similar correlations can be observed when considering different degrees of
freedom of a single system, even a classical one. Surprisingly, it has also
been suggested that entanglement might be playing a relevant role in certain
biological processes, such as the functioning of pigment-proteins that
constitute light-harvesting complexes of photosynthetic bacteria. The aim of
this work is to show that the presence of entanglement in all of these
different scenarios should not be unexpected, once it is realized that the very
same mathematical structure can describe all of them. We show this by
considering three different, realistic cases in which the only condition for
entanglement to exist is that a single excitation is coherently delocalized
between the different subsystems that compose the system of interest
Spatial mode detection by frequency upconversion
The efficient creation and detection of spatial modes of light has become
topical of late, driven by the need to increase photon-bit-rates in classical
and quantum communications. Such mode creation/detection is traditionally
achieved with tools based on linear optics. Here we put forward a new spatial
mode detection technique based on the nonlinear optical process of
sum-frequency generation. We outline the concept theoretically and demonstrate
it experimentally with intense laser beams carrying orbital angular momentum
and Hermite-Gaussian modes. Finally, we show that the method can be used to
transfer an image from the infrared band to the visible, which implies the
efficient conversion of many spatial modes.Comment: Published version, 4 pages, 5 figure
Complementarity relationship between first-order coherence and path distinguishability in an interferometer based on induced coherence
We consider an interferometer based on the concept of induced coherence,
where two signal photons that originate in different second-order nonlinear
crystals can interfere. We derive a complementarity relationship that links the
first-order coherence between the two interfering signal photons with a
parameter that quantifies the distinguishing information regarding the
nonlinear crystal where they originated. Astonishingly, the derived
relationship goes beyond the single-photon regime and is valid for any photon
flux rate generated. We show experimental results in the low photon-flux regime
that confirm the validity of the derived complementarity relationship.Comment: 6 pages, 6 figure
Driven Diffusive Systems: How Steady States Depend on Dynamics
In contrast to equilibrium systems, non-equilibrium steady states depend
explicitly on the underlying dynamics. Using Monte Carlo simulations with
Metropolis, Glauber and heat bath rates, we illustrate this expectation for an
Ising lattice gas, driven far from equilibrium by an `electric' field. While
heat bath and Glauber rates generate essentially identical data for structure
factors and two-point correlations, Metropolis rates give noticeably weaker
correlations, as if the `effective' temperature were higher in the latter case.
We also measure energy histograms and define a simple ratio which is exactly
known and closely related to the Boltzmann factor for the equilibrium case. For
the driven system, the ratio probes a thermodynamic derivative which is found
to be dependent on dynamics
Self-assembly of Clicked Star-Shaped Triazines into Functional Nanostructures
Two non-amphiphilic star-shaped 2, 4, 6-tris(1, 2, 3-triazol-4-yl)-1, 3, 5-triazines showing different behavior in terms of self-assembly and luminescent properties are described. They aggregate in the liquid phase to form low-dimensional nanostructures with a variety of morphologies, such as spherical particles, one-hole hollow spheres, toroids, twisted fibers or helical nanotubes, just by varying the conditions of a straightforward reprecipitation method. Aggregation has an opposite effect concerning the fluorescent properties of the proposed compounds, either causing the enhancement or the quenching of the emission after the self-assembly. Quantum chemical calculations have been also performed to assist in the structural and electronic characterization of the two star-shaped compounds
Phagocytic glioblastoma-associated microglia and macrophages populate invading pseudopalisades
Altres ajuts: This project was supported by grants from the Spanish Ministry of Economy and Competitiveness, and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER;), Generalitat de Catalunya, Spanish Ministry of Science, Innovation and Universities and by the Asociación Española Contra el Cancer (AECC).Hypoxic pseudopalisades are a pathological hallmark of human glioblastoma, which is linked to tumour malignancy and aggressiveness. Yet, their function and role in the tumour development have scarcely been explored. It is thought that pseudopalisades are formed by malignant cells escaping from the hypoxic environment, although evidence of the immune component of pseudopalisades has been elusive. In the present work, we analyse the immunological constituent of hypoxic pseudopalisades using high-resolution three-dimensional confocal imaging in tissue blocks from excised tumours of glioblastoma patients and mimic the hypoxic gradient in microfluidic platforms in vitro to understand the cellular motility. We visualize that glioblastoma-associated microglia and macrophages abundantly populate pseudopalisades, displaying an elongated kinetic morphology across the pseudopalisades, and are oriented towards the necrotic focus. In vitro experiments demonstrate that under hypoxic gradient, microglia show a particular motile behaviour characterized by the increase of cellular persistence in contrast with glioma cells. Importantly, we show that glioblastoma-associated microglia and macrophages utilize fibres of glioma cells as a haptotactic cue to navigate along the anisotropic structure of the pseudopalisades and display a high phagocytic activity at the necrotic border of the pseudopalisades. In this study, we demonstrate that glioblastoma-associated microglia and macrophages are the main immune cells of pseudopalisades in glioblastoma, travelling to necrotic areas to clear the resulting components of the prothrombotic milieu, suggesting that the scavenging features of glioblastoma-associated microglia and macrophages at the pseudopalisades serve as an essential counterpart for glioma cell invasion. In this article, Saavedra-Lopez and colleagues described that glioblastoma-associated microglia and macrophages infiltrate hypoxic pseudopalisades, a well-known invading niche of extremely aggressive brain tumours. They show these highly motile immune cells with great phagocytic capacity as a counterpart of the glioma cell invasion
UHMWPE/HDPE in-reactor blends, prepared by in situ polymerization: synthetic aspects and characterization
This work covers the synthesis and characterization of in-reactor Ultra-High Molecular Weight Polyethylene/
High Density Polyethylene, UHMWPE/HDPE, blends by in situ polymerization in a single reactor, through dual catalyst
immobilization. These blends are synthesized combining two different catalysts (one for each targeted molar mass) co-immobilized
in mesoporous Santa Barbara Amorphous, SBA-15, particles. First, the ethylene polymerization behavior is investigated,
under different polymerization conditions. Then, studies on the thermal, mechanical and rheological characteristics
of the produced in-reactor blends are presented and their performance is compared and discussed in a comprehensive way.
Moreover, the effect of different filler contents on the properties exhibited by the resulting materials is investigated.
Results have shown that these in-reactor UHMWPE/HDPE blends exhibit a complex thermal, mechanical and rheological
behavior, which depends mainly on the proportion between the two polymer components and on the amount of SBA-15.info:eu-repo/semantics/publishedVersio
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