White light lateral shear interferometer with holographic shear lenses and spatial Fourier transform.

Lateral shear interferometer is a simple yet powerful method for testing wavefronts or measuring refractive index changes. Previously, we have reported a method of using two holographic lenses to obtain shear and to generate a spatial frequency carrier, which was used for quantitative analysis. This technique has some advantages such as stability and instantaneous measurements. In this Letter, we report a method of using white light with holographic gratings to obtain shear and also to perform wavefront analysis using the spatial carrier fringes generated at a specific selected wavelength from the white light spectrum. We show that the sensitivity of the setup can be changed by selecting different wavelengths from the spectrum.

One-step index-tunable antireflection coatings from aggregated silica nanoparticles.

We demonstrate a method for producing thickness- and refractive index-tunable antireflection coatings utilizing a one-step spin coating procedure with silica nanoparticle solutions. Aging nanoparticle solutions under controlled pH and temperature induces aggregation, allowing precise control of the porosity and refractive index of the spin-processed coating. Coating thickness measurements as a function of solution aging time and temperature allow for determination of the activation energy of the reaction-limited aggregation process. We demonstrate optimization of the antireflection effect for a single-layer silica nanoparticle coating on glass, and suggest that the aggregation method may be generalized to various other nanoparticle-based assemblies.

A portable fiberoptic ratiometric fluorescence analyzer provides rapid point-of-care determination of glomerular filtration rate in large animals.

Measurement of the glomerular filtration rate (GFR) is the gold standard for precise assessment of kidney function. A rapid, point-of-care determination of the GFR may provide advantages in the clinical setting over currently available assays. Here we demonstrate a proof of principle for such an approach in a pig and dogs, two species that approximate the vascular access and GFR results expected in humans. In both animal models, a sub-millimeter optical fiber that delivered excitation light and collected fluorescent emissions was inserted into a peripheral vein (dog) or central venous access (pig) by means of commercial intravenous catheters. A mixture of fluorescent chimeras of a small freely filterable reporter and large non-filterable plasma volume marker were infused as a bolus, excited by light-emitting diodes, and the in vivo signals detected and quantified by photomultiplier tubes in both species in less than 60 min. Concurrent standardized 6-h iohexol plasma kidney clearances validated the accuracy of our results for both physiologic and a chronic kidney disease setting. Thus, our ratiometric technique allows for both measurement of plasma vascular volume and highly accurate real-time GFR determinations, enabling clinical decision making in real time.