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The clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with one C4 and two C3 plants. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate the important roles of the Δ47 value of CO2 entering the leaf, kinetic fractionation as CO2 diffuses into, and out of the leaf and CO2–H2O isotope exchange with leaf water. We experimentally confirm the previously suggested dependence of Δ47 of CO2 in the air surrounding a leaf on the stomatal conductance and back-diffusion flux. Gas exchange can enrich or deplete the Δ47 of CO2 depending on the Δ47 of CO2 entering the leaf and the fraction of CO2 exchanged with leaf water and diffused back to the atmosphere, but under typical ambient conditions, it will lead to a decrease in Δ47. [ABSTRACT FROM AUTHOR]

Optimizing upconversion (UC) composites is challenging as numerous effects influence their unique emission mechanism. Low scattering mediums increase the number of dopants excited, however, high scattering mediums increase the UC efficiency due to its non-linear power dependency. Scattering also leads to greater thermal effects and emission saturation at lower excitation power density (PD). In this work, a photoluminescence quantum yield (PLQY) increase of 270% was observed when hexagonal NaYF4:(18%)Yb3+,(2%)Er3+ phosphor is in air compared to a refractive index-matched medium. Furthermore, the primary inner-filter effect causes a 94% PLQY decrease when the excitation focal point is moved from the front of the phosphor to 8.4 mm deep. Increasing this effect limits the maximum excitation PD, reduces thermal effects, and leads to emission saturation at higher excitation PDs. Additionally, self-absorption decreases the PLQY as the phosphor's thickness increases from 1 to 9 mm. Finally, in comparison to a cuboid cuvette, a 27% PLQY increase occurs when characterizing the phosphor in a cylindrical cuvette due to a lensing effect of the curved glass, as supported by simulations. Overall, addressing the effects presented in this work is necessary to both maximize UC composite performance as well as report their PLQY more reliably. [ABSTRACT FROM AUTHOR]

This paper presents a new air-bubble free microfluidic blood cuvette for the measurement of hemoglobin concentration. The microfluidic blood cuvette was filled with blood samples by capillary force, and hemoglobin levels in the blood were determined by measuring absorbance at the wavelength of 530 nm. Two different microfluidic blood cuvettes with dual and single sidewall microchannels were investigated. The microfluidic blood cuvette was fabricated using a polymethyl methacrylate substrate and a dry film photoresist. During the blood-filling process, air was trapped in the dual-sided wall-type cuvettes, while no air trapping occurred in the single sidewall-type cuvettes. The sensitivity of the hemoglobin measurements was more linear in a 105 μm deep microchannel than in a 35 μm deep microchannel. [ABSTRACT FROM AUTHOR]

An inexpensive photoreactor using LED light sources and a fibre-optic CCD spectrophotometer as a detector was built by designing a special cell holder for standard 1.000 cm cuvettes. The use of this device was demonstrated by studying the aqueous photochemical reaction of 2,5-dichloro-1,4-benzoquinone. The developed method combines the highly quantitative data collection of CCD spectrophotometers with the possibility of illuminating the sample independently of the detecting light beam, which is a substantial improvement of the method using diode array spectrophotometers as photoreactors. [ABSTRACT FROM AUTHOR]

A modernized device intended for diagnosing the temperature-dependent activity of cells is described. The activity of cells was determined by finding the correlation coefficient of optical signals in speckle patterns recorded at different moments of time. It is shown that, as the temperature increases from 26 to 36°C, variations in the optical paths in cells increase from 16 to 26 nm. This is probably associated with the physiological activity of cells-trapping of large molecules or their conglomerates. In contrast to the previous variant of the device design, instead of a lipid membrane, a cell monolayer was used, which was cultivated on a plane-parallel glass plate. In order to reduce variations in the optical path lengths in a nutrient solution, a 1.7-mm-thick plane-parallel glass plate was additionally inserted into the cuvette. The modernization of the device also includes heating of the cuvette with hot air flows. [ABSTRACT FROM AUTHOR]

We report a multiplexed capillary electrophoresis system employing an array of 32 capillaries with a micromachined sheath-flow cuvette as the detection chamber. The sample streams were simultaneously excited with a 473-nm laser beam, and the fluorescence emission was imaged on a CCD camera with a pair of doublet achromat lens. The instrument produced mass detection limits of 380 ± 120 yoctomoles for fluorescein in zone electrophoresis. Capillary isoelectric focusing of fluorescent standards produced peaks with an average width of 0.0029 ± 0.0008 pH. Capillary coating stability limits the reproducibility of the analysis. [ABSTRACT FROM AUTHOR]

We study experimentally the dynamics of roll domains of the parametrically excited capillary waves. The domain rolls were perpendicular to one another and parallel to different boundaries of a rectangular cuvette. It is found that depending on the initial and boundary conditions, two-dimensional different-shape domains arise at the cuvette edges, and the dynamics of the domain is determined by the motion of their fronts. A model of the observed phenomenon is proposed, which is used for numerical calculations. Simulation results are in good agreement with the experimental evidence. [ABSTRACT FROM AUTHOR]

We have studied the ratio of the intensities of radiation scattered by a layer of blood in a cuvet and by the cuvet walls for normal incidence or incidence at the Brewster angle for probing radiation from a He-Ne laser, linearly polarized in the plane of incidence (plane of observation) or orthogonal to that plane. We have compared it with the intensity of the radiation reflected by the surface of the cuvet wall, as estimated based on the geometric approximation. We have found the optimal conditions for probing and observing scattering for the layer in a cuvet, where such conditions are characterized by a minimal effect from the cuvet walls and the maximum ratio of useful signal to background. [ABSTRACT FROM AUTHOR]

A method intended for increasing the sensitivity of fluorescent analysis of preparations by a factor of 3–15 and ensuring the multiple use of the same sample—for example, in studies of kinetic phenomena on its surface—is described. [ABSTRACT FROM AUTHOR]