Denis Gagnon

Prostaglandins and enzyme secretion from dispersed rat pancreatic acinar cells.

Abstract The role of prostaglandins in exocrine pancreatic enzyme secretion was studied. The effects of three inhibitors of prostaglandin and thromboxane syntheses, were evaluated on release of amylase from dispersed rat pancreatic acinar cells. Mepacrine inhibited, while indomethacin and imidazole had no effect on basal or carbachol or cholecystokinin stimulated enzyme release. Exogenous arachidonic acid or various prostaglandins (E 1 , E 2 , F 2α , I 2 ), also did not affect the secretory process. Acinar cells actively incorporated radioactive arachidonic acid, principally into phospholipids (especially phosphatidylcholine), however release of the free fatty acid and subsequent synthesis of radioactive endogenous prostaglandins was not stimulated by the presence of different pancreatic stimulants. Pancreatic microsomes were found to be lacking in cyclo-oxygenase, an enzyme involved in endegenous synthesis of prostaglandins. The data suggest that prostaglandins are not involved directly in excitation-secretion coupling in the exocrine pancreas.

Beam shaping using genetically optimized two-dimensional photonic crystals.

We propose the use of two-dimensional (2D) photonic crystals (PhCs) with engineered defects for the generation of an arbitrary-profile beam from a focused input beam. The cylindrical harmonics expansion of complex-source beams is derived and used to compute the scattered wave function of a 2D PhC via the multiple scattering method. The beam shaping problem is then solved using a genetic algorithm. We illustrate our procedure by generating different orders of Hermite-Gauss profiles, while maintaining reasonable losses and tolerance to variations in the input beam and the slab refractive index.

Ab initio investigation of lasing thresholds in photonic molecules

We investigate lasing thresholds in a representative photonic molecule composed of two coupled active cylinders of slightly different radii. Specifically, we use the recently formulated steady-state ab initio laser theory (SALT) to assess the effect of the underlying gain transition on lasing frequencies and thresholds. We find that the order in which modes lase can be modified by choosing suitable combinations of the gain center frequency and linewidth, a result that cannot be obtained using the conventional approach of quasi-bound modes. The impact of the gain transition center on the lasing frequencies, the frequency pulling effect, is also quantified.

Toward the formation of crossed laser-induced periodic surface structures

The formation of a new type of laser-induced periodic surface structures using a femtosecond pulsed laser is studied on the basis of the Sipe-Drude theory solved with a FDTD scheme. Our numerical results indicate the possibility of coexisting structures parallel and perpendicular to the polarization of the incident light for low reduced collision frequency (

Multiobjective optimization in integrated photonics design

\gamma/\omega \lesssim 1/4

Pulse shape optimization for electron-positron production in rotating fields

, where

Constructive feedback for the growth of laser‐induced periodic surface structures

\omega

Optimization of integrated polarization filters

is the laser frequency). Moreover, these structures have a periodicity of

Phase space engineering in optical microcavities II. controlling the far-field

\Lambda \sim \lambda

Suppression of Multiphoton Resonances in Driven Quantum Systems via Pulse Shape Optimization

in both orientations. To explain this behavior, light-matter interaction around a single surface inhomogeneity is also studied and confirms the simultaneous presence of surface plasmon polaritons and radiation remnants in orthogonal orientations at low