ABSTRACT
In this Letter, we demonstrate highly efficient, polarization-insensitive planar lenses (metalenses) at red, green, and blue wavelengths (λ = 660, 532, and 405 nm). Metalenses with numerical apertures (NA) of 0.85 and 0.6 and corresponding efficiencies as high as 60% and 90% are achieved. These metalenses are less than 600 nm-thick and can focus incident light down to diffraction-limited spots as small as â¼0.64λ and provide high-resolution imaging. In addition, the focal spots are very symmetric with high Strehl ratios. The single step lithography and compatibility with large-scale fabrication processes make metalenses highly promising for widespread applications in imaging and spectroscopy.
ABSTRACT
The present investigation confirms that initially implemented procedure to produce poly(methylidene malonate 2.1.2) (PMM 2.1.2) nanoparticles (Lescure et al. Pharm Res 1994;11:1270-77) lead to products mostly containing plasticizing oligomers which strongly lowered glass-transition temperature (Tg), dramatically reduced nanoparticle consistency and rendered them too sensitive to solubilization when diluted in an aqueous medium. From MALDI-TOF spectroscopy analysis, performed on intact colloids, emerged some structural information about these oligomeric species which could result from an intramolecular cyclization mechanism occurring soon in the course of the polymerization process. Thus, with the objective of overcoming these drawbacks, this contribution deals with the variations of manufacturing specifications such as pH and magnetic stirring speed to try and modulate molecular weight (MW) of nanoparticle constituents and reduce oligomer concentration. Although the analyses performed on these new nanoparticles were rather encouraging, the colloid formation yield became so low that it required the development of other methodologies, excluding a previous emulsion step, and allowing a controlled production of PMM 2.1.2-made nanoparticles having better physico-chemical characteristics while keeping good pharmaceutical capabilities.
Subject(s)
Biocompatible Materials/chemistry , Malonates/chemistry , Polyethylenes/chemistry , Biocompatible Materials/chemical synthesis , Calorimetry, Differential Scanning , Chemical Phenomena , Chemistry, Physical , Drug Carriers , Malonates/chemical synthesis , Molecular Weight , Particle Size , Polyethylenes/chemical synthesis , Solubility , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , TemperatureABSTRACT
The viscoelastic properties of three classes of soft relining materials (acrylic resins, silicones, and EVA copolymers) were studied comparatively. Their behaviors were investigated by in vitro tests at a frequency omega = 1 Hz, which stimulates the masticatory cycle. The experimental parameter was the temperature (T). Black graphs giving the variations of the stiffness K--proportional to the complex viscoelastic modulus Ex(T) omega--according to the phase angle delta, were used for a predictive approach to increase the comfort of removable dentures. Cole-Cole diagrams, describing the variation of the loss modulus E"(T) omega in relation to the storage modulus E'(T)omega additionally provide quantitative data. The values obtained were related to the noninteger parameter h used for modelization of the viscoelastic behavior of the materials by means of nonlinear Zener models. An attempt was made to correlate the experimental data to the viscoelastic energy loss observed when instability of the prosthetic structure occurs. This attempt takes into account the formation of "cracks" (areas of inadaptation) between the prosthetic intrados and the mucosa.
