Quantitative and Rapid In Vivo Imaging of Human Lenticular Fluorescence.

Purpose: To quantitatively investigate the chemical origins of near-UV excited fluorescence in the crystalline lens, and demonstrate the potential usefulness of a rapid and noninvasive diagnostic approach for screening and monitoring of lens damage.

Methods: Anterior segment UV fluorescence imaging was applied to a population of 30 healthy adults, ages 18 to 64 years. Absolute fluorescence intensities and intensity ratios were compared across the population as a function of age.

Droplet attraction and coalescence mechanism on textured oil-impregnated surfaces.

Droplets residing on textured oil-impregnated surfaces form a wetting ridge due to the imbalance of interfacial forces at the contact line, leading to a wealth of phenomena not seen on traditional lotus-leaf-inspired non-wetting surfaces. Here, we show that the wetting ridge leads to long-range attraction between millimeter-sized droplets, which coalesce in three distinct stages: droplet attraction, lubricant draining, and droplet merging. Our experiments and model show that the magnitude of the velocity and acceleration at which droplets approach each other horizontally is the same as the vertical oil rise velocity and acceleration in the wetting ridge.

Quantitative Spectroscopic Characterization of Near-UV/visible E. coli (pYAC4), B. subtilis (PY79), and Green Bread Mold Fungus Fluorescence for Diagnostic Applications.

Ultraviolet (UV)-excited visible fluorescence is an attractive option for low-cost, low-complexity, rapid imaging of bacterial and fungal samples for imaging diagnostics in the biomedical community. While several studies have shown there is potential for identification of microbial samples, very little quantitative information is available in the literature for the purposes of diagnostic design. In this work, two non-pathogenic bacteria samples (E.

Assessing the Relative Climate Impact of Carbon Utilization for Concrete, Chemical, and Mineral Production.

Estimates show that 6.2 gigatons of carbon dioxide (CO) can be captured and utilized across three pathways, concrete, chemical, and minerals, by 2050. However, it is difficult to compare the climate benefit across these three carbon capture and utilization (CCU) pathways to determine the most effective use of captured CO.

Spiers Memorial Lecture: CO utilization: why, why now, and how?

This introduction to the Faraday Discussion on carbon dioxide utilization (CDU) provides a framework to lay out the need for CDU, the opportunities, boundary conditions, potential pitfalls, and critical needs to advance the required technologies in the time needed. CDU as a mainstream climate-relevant solution is gaining rapid traction as measured by the increase in the number of related publications, the investment activity, and the political action taken in various countries.

Carbon dioxide utilization in concrete curing or mixing might not produce a net climate benefit.

Carbon capture and utilization for concrete production (CCU concrete) is estimated to sequester 0.1 to 1.4 gigatons of carbon dioxide (CO) by 2050.

Human iris three-dimensional imaging at micron resolution by a micro-plenoptic camera.

A micro-plenoptic system was designed to capture the three-dimensional (3D) topography of the anterior iris surface by simple single-shot imaging. Within a depth-of-field of 2.4 mm, depth resolution of 10 µm can be achieved with accuracy (systematic errors) and precision (random errors) below 20%.

High-speed particle image velocimetry near surfaces.

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms.

Single-camera, three-dimensional particle tracking velocimetry.

This paper introduces single-camera, three-dimensional particle tracking velocimetry (SC3D-PTV), an image-based, single-camera technique for measuring 3-component, volumetric velocity fields in environments with limited optical access, in particular, optically accessible internal combustion engines. The optical components used for SC3D-PTV are similar to those used for two-camera stereoscopic-µPIV, but are adapted to project two simultaneous images onto a single image sensor. A novel PTV algorithm relying on the similarity of the particle images corresponding to a single, physical particle produces 3-component, volumetric velocity fields, rather than the 3-component, planar results obtained with stereoscopic PIV, and without the reconstruction of an instantaneous 3D particle field.

High-speed laser-induced fluorescence and spark plug absorption sensor diagnostics for mixing and combustion studies in engines.

Simultaneous high-speed in-cylinder measurements of laser-induced fluorescence of biacetyl as a fuel tracer and mid-infrared broadband absorption of fuel and combustion products (water and carbon dioxide) using a spark plug probe are compared in an optical engine. The study addresses uncertainties and the applicability of absorption measurements at a location slightly offset to the spark plug when information about mixing at the spark plug is desired. Absorbance profiles reflect important engine operation events, such as valve opening and closing, mixing, combustion, and outgassing from crevices.

Attenuation effects on imaging diagnostics of hollow-cone sprays.

Detrimental effects to quantitative interpretation of Mie and laser-induced fluorescence images of hollow-cone sprays were investigated. The attenuation of the laser beam leads to locally unknown intensities rendering it impossible to obtain high-fidelity images of these sprays. Two strategies that use bidirectional illumination of the spray are discussed and evaluated.

Investigation of spatially resolved light absorption in a spark-ignition engine fueled with propane/air.

UV absorption in the combustion phase of spark-ignition engines strongly influences laser-induced-fluorescence measurements and flame-emission techniques because of the attenuation of a laser and/or signal light. This absorption was assessed with spatial, spectral, and temporal resolutions in an optically accessible research engine. Absorption was measured along a line for different crank-angle positions throughout the combustion phase of the engine by use of spectrally resolved transmittance measurements of both broadband illumination from a deuterium lamp and emission of laser-excited hot oxygen.

Quantification of NO A-X (0, 2) laser-induced fluorescence: investigation of calibration and collisional influences in high-pressure flames.

Laser-induced-fluorescence techniques have been used successfully for quantitative two-dimensional measurements of nitric oxide. NO A-X(0, 2) excitation at 248 nm recently found applications in internal-combustion engines. We assess the collisional processes that influence quantification of signal intensities in terms of saturation, rotational energy transfer, and line broadening, using laminar high-pressure methane/air and n-heptane/air flames at pressures as high as 80 bars (8 x 10(6) Pa).

Laser applications to chemical and environmental analysis: introduction to the feature issue.

This issue of Applied Optics features 16 papers describing chemical and environmental measurements made possible by lasers. Many of these contributions were presented at the Optical Society of America Topical Meeting on Laser Applications to Chemical and Environmental Analysis, held in Orlando, Florida, 9-11 March 1998.

Branching ratios for quenching of nitric oxide A 2Sigma+ (nu' = 0) to X 2Pi(nu' = 0).

We describe experiments designed to measure the fraction of nitric oxide molecules that undergo quenching from A 2Sigma+ (nu' = 0) directly to X 2Pi(nu" = 0). This quenching channel was investigated for room temperature collisions with O2, CO, CO2, and H2O by measuring recovery of the ground-state population following intense laser excitation. Experiments were conducted in a room temperature flow cell containing dilute mixtures of NO, N2, and the quenching gases.

High-speed fuel tracer fluorescence and OH radical chemiluminescence imaging in a spark-ignition direct-injection engine.

An innovative technique has been demonstrated to achieve crank-angle-resolved planar laser-induced fluorescence (PLIF) of fuel followed by OH* chemiluminescence imaging in a firing direct-injected spark-ignition engine. This study used two standard KrF excimer lasers to excite toluene for tracking fuel distribution. The intensified camera system was operated at single crank-angle resolution at 2000 revolutions per minute (RPM) for 500 consecutive cycles.

Laser-induced-fluorescence detection of nitric oxide in high-pressure flames with A-X(0, 2) excitation.

Laser-induced fluorescence techniques have been used successfully for quantitative two-dimensional measurements of nitric oxide. The commonly applied D-X(0, 1) or A-X(0, 0) schemes are restricted to atmospheric-pressure flames and engines driven with gaseous fuels because of strong attenuation of the exciting laser beam by combustion intermediates. The properties of a detection scheme for which excitation in the nitric oxide A-X(0, 2) band was used were investigated.

Tunable KrCI excimer-laser operation for combustion diagnostics.

Operating conditions for a tunable XeCl excimer laser have been optimized for tunable narrow-band operation at 222 nm with KrCl, formed in Kr/He/Ne/HCl gas mixtures. This wavelength is interesting for detection of nitric oxide (NO) in combustion environments. The laser emission coincides with the (1, 1) and (2, 2) bands of the NO A-X system.

Detection of methyl radicals in a flat flame by degenerate four-wave mixing.

We report the spatially resolved detection of methyl radicals in a methane-air flat flame, using degenerate four-wave mixing (DFWM). A frequency-tripled dye laser pumped with a frequency-doubled Nd:YAG laser was used to access the Herzberg beta(1) band of methyl near 216 nm. Using a nearly phase-conjugate geometry, we detected methyl with high spatial resolution [0.

Laser in situ monitoring of combustion processes.

Several examples of laser in situ monitoring of combustion processes are presented. Using a frequency modulated (13)CO(2) waveguide laser, in situ concentrations of NH(3) down to 1 ppm were measured at temperatures up to 600 degrees C in waste incinerators and power or chemical plants. Following ignition of CH(3)OH-O(2) mixtures by a TEA CO(2) laser, gas temperature profiles were measured using rapid scanning tunable diode laser spectroscopy of CO molecules.