Liquid crystal doped photopolymer micro-droplets printed by a simple and clean laser-induced forward transfer process.

We print a tunable photopolymer (photopolymer dispersed liquid crystal -PDLC), using the laser-induced direct transfer technique without absorber layer, which was a challenge for this technique given the low absorption and high viscosity of PDLC, and which had not been achieved so far to our knowledge. This makes the LIFT printing process faster and cleaner and achieves a high-quality printed droplet (aspheric profile and low roughness). A femtosecond laser was needed to reach sufficiently peak energies to induce nonlinear absorption and eject the polymer onto a substrate. Only a narrow energy window allows the material to be ejected without spattering.

Homography estimation from a single-point correspondence using template matching and particle swarm optimization.

Existing feature-based methods for homography estimation require several point correspondences in two images of a planar scene captured from different perspectives. These methods are sensitive to outliers, and their effectiveness depends strongly on the number and accuracy of the specified points. This work presents an iterative method for homography estimation that requires only a single-point correspondence. The homography parameters are estimated by solving a search problem using particle swarm optimization, by maximizing a match score between a projective transformed fragment of the input image using the estimated homography and a matched filter constructed from the reference image, while minimizing the reprojection error. The proposed method can estimate accurately a homography from a single-point correspondence, in contrast to existing methods, which require at least four points. The effectiveness of the proposed method is tested and discussed in terms of objective measures by processing several synthetic and experimental projective transformed images.

Wastewater collection system failures in a capital city: analysis and sustainable prevention.

An analysis of failures in a capital city's wastewater collection system was carried out and recommendations were made for sustainable preventive measures based on a risk of failure assessment. Most failures in sewer lines were associated with blockage caused by sediment accumulation and clogging from fats, oils and/or grease dumped by restaurants along several streets, combined with poor or nonexistent maintenance of the lines. Sewer lines in streets with higher risk levels due to multiple food establishments along those streets experienced most of the failures. Sustainability of the proposed maintenance was evidenced since it reduces costs and exposure to harmful substances and hazardous conditions as well as minimizing environmental impacts.

Influence of temporal averaging in the performance of a rotating retarder imaging Stokes polarimeter.

We study the optimum operating conditions for a rotating retarder fixed polarizer (RRFP) when the measurements are not quasi-instantaneous but time-averaged. We obtain the optimum retardance and retarder orientations as a function of the integrated angle interval. We also study how the increase in the number of time-averaged measurements leads to a better equally weighted variance (EWV) value, and thus, to a better performance of the polarimeter in terms of noise amplification for the case of additive noise. Two different analyzers configurations are studied in this work: uniformly spaced retarder angles and when measurements are taken at optimum angles (non-uniformly spaced angles). We also consider the case of polychromatic illumination. We discuss the best measurement conditions in terms of the signal-to-noise ratio depending on whether there is a fixed or a limited amount of photons per measurement.

Unitary matrix approach for a precise voltage dependent characterization of reflective liquid crystal devices by average Stokes polarimetry.

Precise characterization of parallel-aligned liquid crystal on silicon microdisplays has an important impact in many advanced photonics applications. We show liquid crystal on silicon (LCoS) modeled as a non-absorbent reciprocal device. Combined with time-average Stokes polarimetry, LCoS enables us to demonstrate robust measurements across the whole applied voltage range for the retardance and its flicker, and also as a novelty for the director orientation. We obtain that the director orientation changes across the voltage range, especially at larger applied voltages. This is a small effect, but it may provide a deeper insight into the internal dynamics in the liquid crystal layer, and in sensitive phase-only applications will produce a coupling between amplitude and phase.

Combining average molecular tilt and flicker for management of depolarized light in parallel-aligned liquid crystal devices for broadband and wide-angle illumination.

We demonstrate a complete semiphysical and analytical model describing the angular and wavelength dependencies not only of retardance, but also its flicker, in parallel aligned liquid crystal (PA-LC) devices. It relies on the fitting of the molecules' equivalent tilt angle as a function of applied voltage. The wide range of calculations it offers without requiring extensive characterization makes the model unique. We focus on PA-LCoS application as a polarization state generator across the visible spectrum and for a wide range of incidence angles. This approach offers novel capabilities for managing arbitrary states of both full and partial polarization. To highlight the richness of situations with PA-LCoS devices, we provide results for two different digital addressing sequences producing different levels of flicker.

Simplified physical modeling of parallel-aligned liquid crystal devices at highly non-linear tilt angle profiles.

In recent works, we demonstrated the accuracy and physical relevance of a highly simplified reverse-engineering analytical model for a parallel-aligned liquid crystal on silicon devices (PA-LCoS). Both experimental measurements and computational simulations applying the rigorous split-field finite difference time domain (SF-FDTD) technique led to this conclusion in the low applied voltages range. In this paper, we develop a complete rigorous validation covering the full range of possible applied voltages, including highly non-linear liquid crystal (LC) tilt angle profiles. We demonstrate the applicability of the model for spectral and angular retardation calculations, of interest in spatial light modulation applications. We also show that our analytical model enables the calculation of the retardance for novel PA-LC devices as a function of the LC compound and cell gap, becoming an appealing alternative to the usual numerical approaches for PA-LC devices design.

Reasons for Discontinuation and Adverse Effects of TNFα Inhibitors in a Cohort of Patients With Rheumatoid Arthritis and Ankylosing Spondylitis.

BACKGROUND: The introduction of anti-tumor necrosis factor α (anti-TNFα) drugs has improved the clinical outcomes in rheumatoid arthritis (RA) and ankylosing spondylitis (AS). However, these drugs may cause adverse effects that motivate a change in or discontinuation of the treatment. OBJECTIVE: To evaluate the causes of discontinuation or changes in the dosage regimen in a cohort of patients with RA and AS treated with infliximab, adalimumab, etanercept, and golimumab under clinical practice conditions. METHODS: This was a retrospective observational study that included patients with RA or AS treated with anti-TNFα drugs between 2008 and 2013. Changes in the dosage regimen, reasons for treatment discontinuation, and adverse effects were recorded and analyzed. Time to discontinuation was estimated using Kaplan-Meier survival analysis. RESULTS: A total of 123 patients with RA and 93 patients with AS were treated with anti-TNFα therapy. During the study, 55.3% of RA patients and 41.7% of AS patients had stopped the treatment. The most frequent changes were modifications in the dosing, and the most frequent adverse effects were reactions after the infusion or injection (53.8% and 66.7% in RA and AS, respectively). Drug survival of etanercept in RA (67.9%) is greater than for adalimumab and infliximab, whereas drug survival of infliximab in AS (70.0%) is greater than for etanercept and adalimumab at 5 years, although there were no significant differences ( P = 0.098 in RA and 0.194 in AS). CONCLUSIONS: The main cause of discontinuation of anti-TNFα is therapeutic failure in both diseases. Etanercept and infliximab have the best survival rates in RA and AS, respectively.

Molecular evolution constraints in the floral organ specification gene regulatory network module across 18 angiosperm genomes.

The gene regulatory network of floral organ cell fate specification of Arabidopsis thaliana is a robust developmental regulatory module. Although such finding was proposed to explain the overall conservation of floral organ types and organization among angiosperms, it has not been confirmed that the network components are conserved at the molecular level among flowering plants. Using the genomic data that have accumulated, we address the conservation of the genes involved in this network and the forces that have shaped its evolution during the divergence of angiosperms. We recovered the network gene homologs for 18 species of flowering plants spanning nine families. We found that all the genes are highly conserved with no evidence of positive selection. We studied the sequence conservation features of the genes in the context of their known biological function and the strength of the purifying selection acting upon them in relation to their placement within the network. Our results suggest an association between protein length and sequence conservation, evolutionary rates, and functional category. On the other hand, we found no significant correlation between the strength of purifying selection and gene placement. Our results confirm that the studied robust developmental regulatory module has been subjected to strong functional constraints. However, unlike previous studies, our results do not support the notion that network topology plays a major role in constraining evolutionary rates. We speculate that the dynamical functional role of genes within the network and not just its connectivity could play an important role in constraining evolution.

Exploring binary and ternary modulations on a PA-LCoS device for holographic data storage in a PVA/AA photopolymer.

We focus on the novelty of three elements in holographic data storage systems (HDSS): the data pager, where we introduce a parallel-aligned liquid crystal on silicon (PA-LCoS) microdisplay; the recording material, where we consider the highly versatile PVA/AA photopolymer; and also in the architecture of the object arm, where a convergent correlator system is introduced. We show that PA-LCoS devices cannot implement pure hybrid-ternary modulated (HTM) data pages but a rather close approximation. Validation of the HDSS expressions for the convergent correlator and comparison with the widespread 4-f system is performed. Experimental results with PVA/AA material showing bit-error rates (BER) in the range of 10-3, further show its potential application for HDSS, and also demonstrate the validity of the testing platform and PA-LCoS calibration and optimization.

Interferometric characterization of the structured polarized light beam produced by the conical refraction phenomenon.

The interest on the conical refraction (CR) phenomenon in biaxial crystals has revived in the last years due to its prospective for generating structured polarized light beams, i.e. vector beams. While the intensity and the polarization structure of the CR beams are well known, an accurate experimental study of their phase structure has not been yet carried out. We investigate the phase structure of the CR rings by means of a Mach-Zehnder interferometer while applying the phase-shifting interferometric technique to measure the phase at the focal plane. In general the two beams interfering correspond to different states of polarization (SOP) which locally vary. To distinguish if there is an additional phase added to the geometrical one we have derived the appropriate theoretical expressions using the Jones matrix formalism. We demonstrate that the phase of the CR rings is equivalent to that one introduced by an azimuthally segmented polarizer with CR-like polarization distribution. Additionally, we obtain direct evidence that the Poggendorff dark ring is an annular singularity, with a π phase change between the inner and outer bright rings.

Predictive capability of average Stokes polarimetry for simulation of phase multilevel elements onto LCoS devices.

Parallel-aligned (PA) liquid-crystal on silicon (LCoS) microdisplays are especially appealing in a wide range of spatial light modulation applications since they enable phase-only operation. Recently we proposed a novel polarimetric method, based on Stokes polarimetry, enabling the characterization of their linear retardance and the magnitude of their associated phase fluctuations or flicker, exhibited by many LCoS devices. In this work we apply the calibrated values obtained with this technique to show their capability to predict the performance of spatially varying phase multilevel elements displayed onto the PA-LCoS device. Specifically we address a series of multilevel phase blazed gratings. We analyze both their average diffraction efficiency ("static" analysis) and its associated time fluctuation ("dynamic" analysis). Two different electrical configuration files with different degrees of flicker are applied in order to evaluate the actual influence of flicker on the expected performance of the diffractive optical elements addressed. We obtain a good agreement between simulation and experiment, thus demonstrating the predictive capability of the calibration provided by the average Stokes polarimetric technique. Additionally, it is obtained that for electrical configurations with less than 30° amplitude for the flicker retardance, they may not influence the performance of the blazed gratings. In general, we demonstrate that the influence of flicker greatly diminishes when the number of quantization levels in the optical element increases.

Averaged Stokes polarimetry applied to evaluate retardance and flicker in PA-LCoS devices.

Recently we proposed a novel polarimetric method, based on Stokes polarimetry, enabling the characterization of the linear retardance and its flicker amplitude in electro-optic devices behaving as variable linear retarders. In this work we apply extensively the technique to parallel-aligned liquid crystal on silicon devices (PA-LCoS) under the most typical working conditions. As a previous step we provide some experimental analysis to delimitate the robustness of the technique dealing with its repeatability and its reproducibility. Then we analyze the dependencies of retardance and flicker for different digital sequence formats and for a wide variety of working geometries.

Retardance and flicker modeling and characterization of electro-optic linear retarders by averaged Stokes polarimetry.

A polarimetric method for the measurement of linear retardance in the presence of phase fluctuations is presented. This can be applied to electro-optic devices behaving as variable linear retarders. The method is based on an extended Mueller matrix model for the linear retarder containing the time-averaged effects of the instabilities. As a result, an averaged Stokes polarimetry technique is proposed to characterize both the retardance and its flicker magnitude. Predictive capability of the approach is experimentally demonstrated, validating the model and the calibration technique. The approach is applied to liquid crystal on silicon displays (LCoS) using a commercial Stokes polarimeter. Both the magnitude of the average retardance and the amplitude of its fluctuation are obtained for each gray level value addressed, thus enabling a complete phase characterization of the LCoS.

Linearity in the response of photopolymers as optical recording media.

Photopolymer are appealing materials for diffractive elements recording. Two of their properties when they are illuminated are useful for this goal: the relief surface changes and the refractive index modifications. To this goal the linearity in the material response is crucial to design the optimum irradiance for each element. In this paper we measured directly some parameters to know how linear is the material response, in terms of the refractive index modulation versus exposure, then we can predict the refractive index distributions during recording. We have analyzed at different recording intensities the evolution of monomer diffusion during recording for photopolymers based on PVA/Acrylamide. This model has been successfully applied to PVA/Acrylamide photopolymers to predict the transmitted diffracted orders and the agreement with experimental values has been increased.

See-through display based on commercial photopolymer: Optimization and shrinkage effects.

Nowadays augmented reality, 3D Image, mixed reality and see-through applications are very attractive technologies due to their great potential. Holographic optical elements can provide interesting solutions for injection and extraction of the image in the waveguides that are part of the see-through devices. We have developed a coupled waveguide system based on slanted transmission gratings recorded in manufactured photopolymers. In this work we optimize our schedule to a commercial photopolymer for this high demanded application. We demonstrate that high diffraction efficiencies can be obtained if we optimize the recording geometry, recording intensity and recording time for this material. In addition, we study the effects of shrinkage in our holographic system. In general shrinkage is an important drawback for holographic applications, nevertheless we demonstrate how shrinkage can help these systems open new possibilities. Lastly, we show how to significantly improve the quality of the guided image.

Metafiber transforming arbitrarily structured light.

Structured light has proven useful for numerous photonic applications. However, the current use of structured light in optical fiber science and technology is severely limited by mode mixing or by the lack of optical elements that can be integrated onto fiber end-faces for wavefront engineering, and hence generation of structured light is still handled outside the fiber via bulky optics in free space. We report a metafiber platform capable of creating arbitrarily structured light on the hybrid-order Poincaré sphere. Polymeric metasurfaces, with unleashed height degree of freedom and a greatly expanded 3D meta-atom library, were 3D laser nanoprinted and interfaced with polarization-maintaining single-mode fibers. Multiple metasurfaces were interfaced on the fiber end-faces, transforming the fiber output into different structured-light fields, including cylindrical vector beams, circularly polarized vortex beams, and arbitrary vector field. Our work provides a paradigm for advancing optical fiber science and technology towards fiber-integrated light shaping, which may find important applications in fiber communications, fiber lasers and sensors, endoscopic imaging, fiber lithography, and lab-on-fiber technology.

Adsorption of Pb (II) ions on variable charge oxidic calcined substrates with chemically modified surface.

Background: The paper describes lead ion adsorption on variable charge oxidic calcined substrates with chemically modified surfaces. Amphoteric oxides of iron, aluminum, titanium, and manganese, change their surface electric charge after acid or alkaline treatment, letting cationic or anionic adsorption reactions from aqueous solutions. This property allows using them as adsorbing substrate for heavy metals retention in water treatment systems. Methods: Substrate was prepared by extruding cylindrical strips from a saturate paste of the oxidic lithological material-OLM; dries it up and thermally treated by calcination. The study was performed by triplicated trial, on batch mode, using 2 grams samples of treated with NaOH 0.1N and non-treated substrate. Lead analysis was performed by AAS-GF. Freundlich and Langmuir models were used to fit results. Comparing differential behavior between treated and non-treated substrates showed the variable charge nature of the OLM. Results: Results show L-type isotherms for the adsorption of Pb(II) ions on the activated substrate, suggesting good affinity between Pb(II) ions and OLM's surface. Average value of adsorption capacity ( K) for activated substrate (1791.73±13.06), is around four times greater than the non-activated substrate (491.54±31.97), during the adsorption reaction, 0.35 and 0.26 mmolH + of proton are produced on the activated and non-activated substrate respectively using a 1 mM Pb(II) solution and 72.2 and 15.6 mmolH + using a 10 mM Pb(II) solution. This acidification agrees with the theoretic model of transitional metals chemisorption on amphoteric oxides, present in lithological material used for the preparation of adsorbent substrates, confirming the information given by the L-type isotherms. Conclusions: Results suggest that these variable charge oxidic adsorbent substrate show great potential as an alternative technique for water treatment at small and medium scale using granular filtration system. The easiness and low price make them suitable to apply in rural media where no treating water systems is available.

Laser transfer for circulating tumor cell isolation in liquid biopsy.

75Cancer research has found in the recent years a formidable ally in liquid biopsy, a noninvasive technique that allows the study of circulating tumor cells (CTCs) and biomolecules involved in the dynamics of cancer spread like cell-free nucleid acids or tumor-derived extracellular vesicles. However, single-cell isolation of CTCs with high viability for further genetic, phenotypic, and morphological characterization remains a challenge. We present a new approach for single CTC isolation in enriched blood samples using a liquid laser transfer (LLT) process, adapted from standard laser direct write techniques. In order to completely preserve the cells from direct laser irradiation, we used an ultraviolet laser to produce a blister-actuated laser-induced forward transfer process (BA-LIFT). Using a plasma-treated polyimide layer for blister generation, we completely shield the sample from the incident laser beam. The optical transparency of the polyimide allows direct cell targeting using a simplified optical setup, in which the laser irradiation module, standard imaging, and fluorescence imaging share a common optical path. Peripheral blood mononuclear cells (PBMCs) were identified by fluorescent markers, while target cancer cells remained unstained. As a proof of concept, we were able to isolate single MDA-MB-231 cancer cells using this negative selection process. Unstained target cells were isolated and culture while their DNA was sent for single-cell sequencing (SCS). Our approach appears to be an effective approach to isolate single CTCs, preserving cell characteristics in terms of cell viability and potential for further SCS.

Precise-Integration Time-Domain Formulation for Optical Periodic Media.

A numerical formulation based on the precise-integration time-domain (PITD) method for simulating periodic media is extended for overcoming the Courant-Friedrich-Levy (CFL) limit on the time-step size in a finite-difference time-domain (FDTD) simulation. In this new method, the periodic boundary conditions are implemented, permitting the simulation of a wide range of periodic optical media, i.e., gratings, or thin-film filters. Furthermore, the complete tensorial derivation for the permittivity also allows simulating anisotropic periodic media. Numerical results demonstrate that PITD is reliable and even considering anisotropic media can be competitive compared to traditional FDTD solutions. Furthermore, the maximum allowable time-step size has been demonstrated to be much larger than that of the CFL limit of the FDTD method, being a valuable tool in cases in which the steady-state requires a large number of time-steps.