228 research outputs found
Light Engineering of the Polariton Landscape in Semiconductor Microcavities
We demonstrate a method to create potential barriers with polarized light
beams for polaritons in semiconductor microcavities. The form of the barriers
is engineered via the real space shape of a focalised beam on the sample. Their
height can be determined by the visibility of the scattering waves generated in
a polariton fluid interacting with them. This technique opens up the way to the
creation of dynamical potentials and defects of any shape in semiconductor
microcavities.Comment: 4 pages, 5 figure
Enrichment of innate lymphoid cell populations in gingival tissue
Innate lymphoid cells (ILCs) are a population of lymphocytes that act as the first line of immunologic defense at mucosal surfaces. The ILC family in the skin, lungs, and gastrointestinal tissues has been investigated, and there are reports of individual subsets of ILCs in the oral tissues. We sought to investigate the whole ILC population (group 1, 2, and 3 subsets) in the murine gingivae and the lymph nodes draining the oral cavity. We show that ILCs made up a greater proportion of the whole CD45+ lymphocyte population in the murine gingivae (0.356% ± 0.039%) as compared with the proportion of ILCs in the draining lymph nodes (0.158% ± 0.005%). Cytokine profiling of the ILC populations demonstrated different proportions of ILC subsets in the murine gingivae versus the regional lymph nodes. The majority of ILCs in the draining lymph nodes expressed IL-5, whereas there were equal proportions of IFN-γ- and IL-5 expressing ILCs in the oral mucosa. The percentage of IL-17+ ILCs was comparable between the murine gingivae and the oral draining lymph nodes. These data suggest an enrichment of ILCs in the murine gingivae, and these ILCs reflect a cytokine profile discrepant to that of the local draining lymph nodes. These studies indicate diversity and enrichment of ILCs at the oral mucosal surface. The function of ILCs in the oral cavity remains to be determined; here, we provide a premise of ILC populations that merits future consideration in investigations of mouse models and human tissues
Spin rings in bi-stable planar semiconductor microcavities
A unique feature of exciton-polaritons, inherited from their mixed
light-matter origin, is the strongly spin-dependent polariton-polariton
interaction, which has been predicted to result in the formation of spin rings
in real space [Shelykh et al., Phys. Rev. Lett. 100, 116401 (2008)]. Here we
experimentally demonstrate the spin bi-stability of exciton-polaritons in an
InGaAs-based semiconductor microcavity under resonant optical pumping. We
observe the formation of spin rings whose size can be finely controlled in a
spatial scale down to the micrometer range, much smaller than the spot size. We
additionally evaluate the sign and magnitude of the antiparallel polariton spin
interaction constant.Comment: 5 pages, 4 figure
Polarization bistability and resultant spin rings in semiconductor microcavities
The transmission of a pump laser resonant with the lower polariton branch of
a semiconductor microcavity is shown to be highly dependent on the degree of
circular polarization of the pump. Spin dependent anisotropy of
polariton-polariton interactions allows the internal polarization to be
controlled by varying the pump power. The formation of spatial patterns, spin
rings with high degree of circular polarization, arising as a result of
polarization bistability, is observed. A phenomenological model based on spin
dependent Gross-Pitaevskii equations provides a good description of the
experimental results. Inclusion of interactions with the incoherent exciton
reservoir, which provides spin-independent blueshifts of the polariton modes,
is found to be essential.Comment: 5 pages, 3 figure
Anisotropic Optical Spin Hall Effect in Semiconductor Microcavities
Propagating, directionally dependent, polarized spin-currents are created in
an anisotropic planar semiconductor microcavity, via Rayleigh scattering of
optically injected polaritons in the optical spin Hall regime. The influence of
anisotropy results in the suppression or enhancement of the pseudospin
precession of polaritons scattered into different directions. This is exploited
to create intense spin currents by excitation on top of localized defects. A
theoretical model considering the influence of the total effective magnetic
field on the polariton pseudospin quantitatively reproduces the experimental
observations.Comment: 4 pages, 4 figure
Motion of spin polariton bullets in semiconductor microcavities
The dynamics of optical switching in semiconductor microcavities in the strong coupling regime is studied by using time- and spatially resolved spectroscopy. The switching is triggered by polarized short pulses which create spin bullets of high polariton density. The spin packets travel with speeds of the order of 106 m/s due to the ballistic propagation and drift of exciton polaritons from high to low density areas. The speed is controlled by the angle of incidence of the excitation beams, which changes the polariton group velocityWe thank R. Houdré for the microcavity sample. This work was supported by the IFRAF, the Agence Nationale pour la Recherche, the Spanish MEC (MAT2008-01555 and QOIT-CSD2006-00019), CAM (S-2009/ESP-1503) and FP7 ITN’s ‘‘Clermont4’’ (235114), and Spin-optronics (237252). We acknowledge the Institut Universitaire de Franc
Interleukin 18 maintains a long-standing inflammation in coeliac disease patients
Producción CientíficaDietary gluten induces an early response in the intestine of coeliac disease
patients (CD), within a few hours, and this is driven by high levels of proinflammatory
cytokines, including IFNg and IL-15, as has been thoroughly
shown by gluten stimulation of biopsy explants. Our aim was to identify the
immune mediators involved in the long-standing inflammation in untreated
CD patients at diagnosis. mRNA and protein levels of TNFa, IL-12(p35),
IL-12(p40), IL-15, IL-18 and IL-23(p19) were quantified in biopsies from
active CD patients, CD patients on a gluten-free diet (GFD), healthy controls,
and patients with non-CD inflammation and mild histological changes in the
intestine. Biopsies from CD patients on a GFD were also stimulated in vitro
with gliadin, and protein expression of IL-15 and IL-18 was analysed. Levels of
IL-12 and IL-23 mRNA are nearly absent, and TNFa levels remain unchanged
among different groups. Both the active and inactive forms of IL-18 protein
have been found in all samples from active CD, and protein expression was
only localized within the crypts. Levels of IL-15 mRNA remain unchanged,
and protein expression, localized within the lamina propria, is found in a
small number of samples. In vitro stimulation with gluten induces the expression
of IL-15 and IL-18. In active CD, the early response following gluten
intake characterized by high IFNg levels is driven by IL-18, and probably
IL-15, and this alternates with periods of long-standing inflammation with
moderate IFNg levels, maintained by IL-18 alone
Discriminant Analysis of Geographical Origin of Cork Planks and Stoppers by Near Infrared Spectroscopy
The objective of this study was to assess the potential of visible and near infrared spectroscopy (VIS+NIRS) combined with multivariate analysis for identifying the geographical origin of cork. The study was carried out on cork planks and natural cork stoppers from the most representative cork-producing areas in the world. Two training sets of international and national cork planks were studied. The first set comprised a total of 479 samples from Morocco, Portugal, and Spain, while the second set comprised a total of 179 samples from the Spanish regions of Andalusia, Catalonia, and Extremadura. A training set of 90 cork stoppers from Andalusia and Catalonia was also studied. Original spectroscopic data were obtained for the transverse sections of the cork planks and for the body and top of the cork stoppers by means of a 6500 Foss-NIRSystems SY II spectrophotometer using a fiber optic probe. Remote reflectance was employed in the wavelength range of 400 to 2500 nm. After analyzing the spectroscopic data, discriminant models were obtained by means of partial least square (PLS) with 70% of the samples. The best models were then validated using 30% of the remaining samples. At least 98% of the international cork plank samples and 95% of the national samples were correctly classified in the calibration and validation stage. The best model for the cork stoppers was obtained for the top of the stoppers, with at least 90% of the samples being correctly classified. The results demonstrate the potential of VIS + NIRS technology as a rapid and accurate method for predicting the geographical origin of cork plank and stopper
Field sampling of cork value before extraction in Portuguese "montados"
The assessment of cork quality and the
estimation of cork value are very important to forest
landowners, for management purposes and for cork
commercialisation. The Forest Producers Associations
have been using a sampling scheme with the objective
of estimating cork value (price per unit of weight,
usually kg) before extraction, based on the sampling of
individual trees along a zigzag transect that covers the
entire stand. The sampling error is usually too high,
but, from a practical standpoint, it is difficult to
increase the sampling intensity if it would imply an
increase in sampling costs. The aim of this work was to
propose, from data collected in six stands representative
of the cork oak stands in Portugal, an alternative
sampling methodology with a more efficient precision/
cost ratio. Precision and costs of alternative sampling
designs based on clusters of different sizes, complemented
with analysis of the intracluster correlation
coefficient, were studied in order to propose the most
adequate sampling strategy. Single-stage cluster sampling
with clusters of 5–7 trees guarantees a reasonable
sampling error (10–15%) and can be conducted
without a large increase in cos
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