Effect of non-zero relative velocity on the flame speed of two-phase laminar flames

A numerical study of one-dimensional n-heptane/air spray flames is presented. The objective is to evaluate the flame propagation speed in the case where droplets evaporate inside the reaction zone with possibly non-zero relative velocity. A Direct Numerical Simulation approach for the gaseous phase is coupled to a discrete particle Lagrangian formalism for the dispersed phase. A global two-step n-heptane/air chemical mechanism is used. The effects of initial droplet diameter, overall equivalence ratio, liquid loading and relative velocity between gaseous and liquid phases on the laminar spray flame speed and structure are studied. For lean premixed cases, it is found that the laminar flame speed decreases with increasing initial droplet diameter and relative velocity. On the contrary, rich premixed cases show a range of diameters for which the flame speed is enhanced compared to the corresponding purely gaseous flame. Finally, spray flames controlled by evaporation always have lower flame speeds. To highlight the controlling parameters of spray flame speed, approximate analytical expressions are proposed, which give the correct trends of the spray flame propagation speed behavior for both lean and rich mixtures.     

Integrated all-optical pulse regenerator in chalcogenide waveguides

We report a fully integrated, passive, all-optical regenerator capable of terabit per second operation, based on a highly nonlinear chalcogenide (As2S3) glass rib waveguide followed by an integrated Bragg grating bandpass filter. We demonstrate a clear nonlinear power transfer curve with 1.4 ps optical pulses, capable of improving the signal-to-noise ratio and reducing the bit error rate for digital signals.     

Effect of ligand-affinity differences of human hemoglobin variants on electrophoretic behavior and their isolation and functional characterization

A natural sulfated polysaccharide (agaropectin), contained in crude agar, can be used as a medium for electrophoretic separation of hemoglobin mutants, constituting a particular class of protein-ligand interactions. Mutations which either modify the electrostatic charge at the surface of the hemoglobin molecule or not, have been studied according to their putative interaction with the medium. Using conformational specificities of the hemoglobin molecule, we have also demonstrated that isoelectric focusing on a polyacrylamide gel in the absence of heme ligands represents a useful, convenient and rapid procedure for isolating silent Hb variants in their native form, provided that they exhibit an abnormal Bohr effect.     

Ultraviolet Light‐Induced Cyclobutane Pyrimidine Dimers in Rabbit Eyes

Sunlight exposure of the eye leads to pathologies including photokeratitis, cortical cataracts, pterygium, actinic conjunctivitis and age‐related macular degeneration. It is well established that exposure to ultraviolet (UV) radiations leads to DNA damage, mainly cyclobutane pyrimidine dimers (CPDs). CPD formation is the principal factor involved in skin cancer. However, the exact mechanism by which sunlight induces ocular pathologies is not well understood. To shed light on this issue, we quantified the CPD formation onto DNA of rabbit ocular cells following UVB exposure. We found that CPDs were induced only in the structures of the ocular anterior chamber (cornea, iris and lens) and were more concentrated in the corneal epithelium. Residual UVB that pass through the cornea are completely absorbed by the anterior layers of the iris. CPDs were also detected in the central portion of the lens that is not protected by the iris (pupil). By determining the UV‐induced DNA damage formation in eyes, we showed that anterior ocular structures are a reliable physical barrier that protects the subjacent structures from the toxic effects of UV. Although the corneal epithelium is the structure where most of the CPDs were detected, no cancer is related to solar exposure.     

Broadband self-pulsating fiber laser based on soliton self-frequency shift and regenerative self-phase modulation

We demonstrate experimentally and numerically the operation of a self-pulsating fiber laser based on the cascaded effects of soliton self-frequency shift and self-phase modulation spectral broadening. The combination of those two effects triggers and sustains the propagation of picosecond pulses in the cavity. At one of the outputs, the laser emits a supercontinuum with spectral width in excess of 150 nm at the repetition rate of 95 kHz.     

Fabrication and characterization of a pulsed fiber ring laser based on As2S3

We demonstrate the operation of a fiber ring laser using a 19.5 cm segment of As2S3 chalcogenide fiber. The laser is passively mode-locked via nonlinear polarization rotation and provides two different operation regimes of picosecond and noiselike pulses. This ring configuration also enables an accurate measurement of the chromatic dispersion of the chalcogenide fiber.