Optical Crosstalk in InGaAs/InP SPAD Array: Analysis and Reduction with FIB-Etched Trenches

This letter describes the reduction of optical crosstalk by means of focused ion beam-etched trenches in InGaAs/InP single-photon avalanche diode arrays. Platinum-filled trenches have been fabricated in a linear array in order to limit the direct optical crosstalk between neighboring pixels. Experimental measurements prove that optical crosstalk has been reduced by ∼60 % thanks to a strong suppression of direct optical paths. An optical model is introduced in order to describe the main contributions to crosstalk and to validate measurements

Recent Advances in Time-resolved Nir Spectroscopy for Nondestructive Assessment of Fruit Quality

Non-destructive monitoring of food internal attributes by near infrared spectroscopy (NIRS) is typically performed by the continuous wave (CW) technique, where steady state light sources (e.g. lamp or LED with constant intensity in time) and photodetectors (e.g. photodiode or charge coupled device camera) are used to measure light attenuation. Indeed light scattering can largely affect light attenuation resulting in the need of calibration for each new batch of samples. To tackle this effect time-resolved NIRS (TRS) has been proposed to improve the classical CW approach to NIRS. The main feature of TRS is its ability to retrieve information on photon path-length in a diffusive medium (generally much larger than the geometrical distance between source and detector). The use of TRS in combination with proper physical models for photon migration allows for the complete optical characterisation with the simultaneous non-destructive measurement of the optical properties (absorption and scattering) of a diffusive medium. This can be of special interest for most fruits and vegetables as well as for other foods (e.g. meat, fish, and cheese), because information derived by TRS refers to the internal properties of the medium, and is not so much affected by surface features as is the case for CW spectroscopy. In the past TRS measurements were possible only with complex laboratory instrumentation consisting of picosecond pulsed lasers, water cooled photomultiplier tubes, and electronic chain for timecorrelated single photon counting. In this work we present the recent advances in TRS technology (laser, detectors and acquisition electronics) that allow the design of portable instrumentation for use in the preharvest (i.e. in the field) and post-harvest

Vortex stability and permanent flow in nonequilibrium polariton condensates

The following article appeared in Journal of Applied Physics 109.10 (2011): 102406 and may be found at http://scitation.aip.org/content/aip/journal/jap/109/10/10.1063/1.3576151We study the effects of imprinting a single-quantized vortex on the steady state of a microcavity exciton-polariton condensate generated via parametric scattering. Interestingly we observe two distinct regimes: In the first case, at low polariton densities, the effect of the pulsed probe, containing the vortex state, is to generate a gain response in the condensate lasting for tens of picoseconds during which no dissipation of the circulating currents is detected. In the second regime, at higher densities, the gain lasts much less and the circulation is imprinted directly into the steady state, which acquires permanent rotation for as long as the vortex remains within the condensate. We use two different ways of measuring the circulation of the condensate and demonstrate that in both cases, polariton condensation in the parametric scattering regime can sustain permanent supercurrentsThis work was partially supported by the Spanish MEC (MAT2008-01555 and QOIT-CSD2006-00019), the CAM (S2009/ESP-1503) and FP7 ITNs “Clermont4” (235114). D.S. acknowledges financial support from the Ramón y Cajal program. G.T. is grateful for the FPI scholarship from the Ministerio de Ciencia e Innovació

Fast-Gated Single-Photon Avalanche Diode for Wide Dynamic Range Near Infrared Spectroscopy

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Solitary fibrous tumor of the pleura presenting with syncope episodes when coughing

<p>Abstract</p> <p>Background</p> <p>Solitary fibrous tumor of the pleura is a rarely encountered clinical entity which may have different clinical pictures. Although the majority of these neoplasms have a benign course, the malignant form has also been reported.</p> <p>Case presentation</p> <p>We herein describe a case of 72 year-old man with head, facial, and thoracic traumas caused by neurally-mediated situational syncope when coughing. The diagnostic work-up including chest x-ray, CT and PET, revealed a large solitary mass of the left hemithorax. Radical surgical resection of the mass was performed through a left lateral thoracotomy and completed with a wedge resection of the lingula. Hystological examination of the surgical specimen showed an encapsulated mass measuring 12 × 11.5 × 6 cm consistent with a solitary fibrous tumor of the pleura. It's surgical removal definitively resolved the neurologic manifestations. The patient had no postoperative complications. At two years follow-up the patient is free from recurrence and without clinical manifestations.</p> <p>Conclusion</p> <p>In our case its resection definitively resolved the episodes of situational syncope due, in our opinion, to the large thoracic mass compressing the phrenic nerve</p

The Molecular and Cellular Basis of Tumor Rejection After Vaccination With Mammary Adenocarcinoma Cells Transduced With the MHC Class II Transactivator CIITA

CD8+ T cell responses are major players of tumor eradication in various vaccination protocols. However, an optimal stimulation of CD4+ T helper cells is required for both priming and maintenance of the effector CTL response against the tumor. In this study we show that the murine mammary adenocarcinoma cell line TS/A, a highly malignant MHC-II-negative tumor, is rejected in vivo if genetically engineered to express MHC-II molecules by transfer of the MHC-II transactivator CIITA. TS/ACIITA cells are fully rejected by 93% of the syngeneic recipients and have a significantly lower growth rate in the remaining 7% of animals. Rejection requires CD4+ and CD8+ cells. CD4+ T cells are fundamental in the priming phase, whereas CTLs are the major anti-tumor effectors. All tumor rejecting animals are protected against rechallenge with the parental TS/A tumor. Immunohistochemical data at day 5 post-inoculation showed an higher infiltrate of CD4+ T cells in mice bearing TS/A-CIITA, than in mice bearing the TS/A tumor. Subsequently, from day 7 trough day 10, TS/A-CIITA tumors showed higher number of both CD4+ and CD8+ cells, dendritic cells, together with massive necrosis. The frequency of IFN-αsecreting splenocytes early after inoculations was also assessed by an ex vivo ELISPOT assay. Only the rejecting TS/A-CIITA animals showed an high frequency of IFN-αsecreting cells (between 80 and 120/106 splenocytes). Importantly, CD4 and CD8 depletion experiments revealed that at the time of tumor resolution the major cell population recognizing the TS/A-CIITA cells was of CD4 origin. This is the first example of successful tumor vaccination by genetic transfer of CIITA. These results open the way to a possible use of CIITA for increasing both the inducing and the effector phase of the anti-tumor response. from 2005 International Meeting of The Institute of Human Virology Baltimore, USA, 29 August – 2 September 200

Non-contact time-resolved diffuse reflectance imaging at null source-detector separation

We report results of the proof-of-principle tests of a novel non-contact tissue imaging system. The system utilizes a quasi-null source-detector separation approach for time-domain near-infrared spectroscopy, taking advantage of an innovative state-of-the-art fast-gated single photon counting detector. Measurements on phantoms demonstrate the feasibility of the non-contact approach for the detection of optically absorbing perturbations buried up to a few centimeters beneath the surface of a tissue-like turbid medium. The measured depth sensitivity and spatial resolution of the new system are close to the values predicted by Monte Carlo simulations for the inhomogeneous medium and an ideal fast-gated detector, thus proving the feasibility of the non-contact approach for high density diffuse reflectance measurements on tissue. Potential applications of the system are also discussed. © 2011 Optical Society of America

Effects of time-gated detection in diffuse optical imaging at short source-detector separation

The adoption of a short source-detector distance, combined with a time-resolved acquisition, can be advantageous in diffuse optical imaging due to the stricter spatial localization of the probing photons, provided that the strong burst of early photons is suppressed using a time-gated detection scheme. We propose a model for predicting the effect of the time-gated measurement system using a time-variant operator built on the system response acquired at different gate delays. The discrete representation of the system operator, termed Spread Matrix, can be analyzed to identify the bottlenecks of the detection system with respect to the physical problem under study. Measurements performed on tissue phantoms, using a time-gated single-photon avalanche diode and an interfiber distance of 2 mm, demonstrate that inhomogeneities down to 3 cm can be detected only if the decay constant of the detector is lower than 100 ps, while the transient opening of the gate has a less critical impact