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A minimally invasive needle refractometer is presented for sugar content measurements within produce. A passive sampling cap structure was developed that improves the reliability of the device by avoiding interfering back reflections from the flesh of the produce. It is explained that factory calibration may not be needed for this type of refractometer, potentially reducing production costs. Also demonstrated is an iterative method to correct for temperature variations without the need for an integrated model for how the refractive index changes with temperature for different levels of sugar concentration. The sensor showed a typical standard deviation of 0.4 °Bx for a 10-s-long measurement and was validated against a prism refractometer, showing an average offset of (0.0 ± 0.1) °Bx. In addition, the potential for using the device to investigate sugar distributions within a single fruit sample is demonstrated. [ABSTRACT FROM AUTHOR]

Background: Almost 80 years after implementation of the industrial ethanol fractionation process, based on the pioneering work of Edwin J. Cohn's research group, it has not lost its importance in providing life-saving biotherapies to patients. The focus has shifted from albumin, which was first used to treat intensive care patients, to immunoglobulin G preparations. Nowadays the latter enables effective, life-long treatment of patients suffering from immunodeficiencies. Ethanol concentration, pH, temperature, protein, and salt concentration are diligently varied during the Cohn fractionation process to finally yield fractions in which the main plasma proteins are enriched at adequate purity. Total protein concentration of the intermediates, probably not as important as ethanol levels and pH, has nevertheless an indisputable influence on the process' performance Objectives: Total protein measurement is therefore a valuable in process-control for versatile process performance monitoring. For this purpose, we investigated the application of analytical digital refractometry. Design: For our pilot study, we used six consecutive batches of nine relevant intermediates covering Takeda's whole industrial-scale Cohn Fractionation process. Methods: Total protein concentrations of the intermediates were measured with the method of Kjehldal to obtain reference data and digital analytical refractometry, using 10-kDa ultrafiltration to obtain a protein free permeate serving as a sample-specific blank. Results and Conclusions: Specific refractive index increment dn/dc values, allowing the calculation of the total protein concentrations by refractive index measurement, were obtained for the Cohn Fractionation intermediates investigated. Thus, analytical digital refractometry, a simple, fast, and robust technique, was shown to be fit for this purpose. [ABSTRACT FROM AUTHOR]

Single-isotherm n(p, T90) results are reported for the gases Ar, N2, H2O, and D2O at vacuum wavelength λ = 1542.383 (1) nm. The argon and nitrogen isotherms were measured near 303 K; the water isotherms were measured near 373 K. Combined with the two previous articles of this series, the present results beget several insights via dispersion analyses. The argon result is highly consistent with static measurement plus ab initio calculation of dispersion polarizability. The nitrogen result is nominally consistent with one recent experiment and the dipole oscillator strength distributions, but the present work offers a refined estimate of the molar refractivity at optical wavelengths. For ordinary and heavy water, the dispersion trend is nominally consistent with existing liquid measurements. However, water's absorption features in the near-infrared preclude a reliable comparison of the present result with literature. [ABSTRACT FROM AUTHOR]

A suite of measurements of refractive index n (p , T 90) is reported for gas phase ordinary water H 2 O and heavy water D 2 O. The methodology is optical refractive index gas metrology, operating at laser wavelength 633 nm and covering the range (293 < T 90 < 433) K and p < 2 kPa . A key output of the work is the determination of molar polarizabilities A R = 3.7466 (18) · [ 1 + 1.5 (6) × 10 - 6 (T / K - 303) ] cm 3 · mol - 1 for ordinary water, and A R = 3.7135 (18) · [ 1 + 4.4 (10) × 10 - 6 (T / K - 303) ] cm 3 · mol - 1 for heavy water, with the numbers in parentheses expressing standard uncertainty. For heavy water, this work appears to be only the second gas phase measurement to date. For both ordinary and heavy water, this work agrees within 0.15 % with recent ab initio theoretical results for A R , but the comparison is affected by imperfect knowledge of dispersion. For ordinary water, the close agreement between the present work and theory suggests problems at the 2 % level in the low density limit of the reference formulation for refractivity. [ABSTRACT FROM AUTHOR]

Determining the quantitative and qualitative composition of solutes is an important scientific and applied problem that arises in various fields of science and technology. However, in a number of practical problems there is a need to determine the concentration of substances whose mass (volume) fraction in the solution is quite small. Common measurement methods, characterized by high speed and versatility are refractometric methods. Of particular interest among refractometric methods in the measurement of low concentrations of solutes is the method based on the use of the effect of surface plasmon resonance. The main advantages of this method are its high sensitivity and low weight of the sample used in the study. To date, the widespread use of this method of measurement is significantly limited by the lack of high-precision mathematical models of primary measuring transducers (sensors) implemented on its basis. The main directions of refractometry development and its relevance in various spheres of human activity, such as science, technology, medicine and even the food industry, were considered in the work. As a result of the need to use the phenomenon of surface-plasmon effect, a detailed description of this phenomenon, its features, nature and practical application. The peculiarity of the interaction of radiation with gold nanofilms is considered. A mathematical model of the refractometer based on the surface plasmon effect was developed. The adequacy of the obtained conclusions was confirmed by means of computer modeling and experimental research. The design of a means of measuring small concentrations of dissolved substances, built on the basis of the described sensor, has been developed. It is shown that such a measuring tool will be characterized by relative simplicity of construction while preserving all the advantages of the refractometric measurement method. [ABSTRACT FROM AUTHOR]

An n (p , T 90) measurement suite is reported for the gases helium, argon, and nitrogen. The methodology is optical refractive-index gas metrology, operating at laser wavelength 633 nm and covering the temperature range (293 < T < 433) K and pressures p < 0.5 MPa . The measurement suite produces several things of thermophysical interest. First, the helium dataset deduces the effective compressibility of the apparatus with a relative standard uncertainty of 1.3 × 10 - 4 . Next, the argon dataset determines T - T 90 with a relative standard uncertainty of about 3 μ K · K - 1 . (The implementation is relative primary thermometry; T - T 90 is the difference between thermodynamic temperature and ITS-90.) Finally, the nitrogen dataset estimates the temperature dependence of polarizability within 3.5 % relative standard uncertainty. As a by-product of the nitrogen and argon measurements, values of the second density virial coefficient B ρ (T) are derived with uncertainties smaller than those of previous experiments. More broadly, the work enables conversion of a measured refractivity at known temperature to optical pressure within 3.5 μ Pa · Pa - 1 across the stated range, albeit traceable to the diameter of a piston-gage. [ABSTRACT FROM AUTHOR]

Medium polarity plays a crucial role in charge-transfer processes and electrochemistry. The added supporting electrolyte in electrochemical setups, essential for attaining the needed electrical conductivity, sets challenges for estimating medium polarity. Herein, we resort to Lippert–Mataga–Ooshika (LMO) formalism for estimating the Onsager polarity of electrolyte organic solutions pertinent to electrochemical analysis. An amine derivative of 1,8-naphthalimide proves to be an appropriate photoprobe for LMO analysis. An increase in electrolyte concentration enhances the polarity of the solutions. This effect becomes especially pronounced for low-polarity solvents. Adding 100 mM tetrabutylammonium hexafluorophosphate to chloroform results in solution polarity exceeding that of neat dichloromethane and 1,2-dichloroethane. Conversely, the observed polarity enhancement that emerges upon the same electrolyte addition to solvents such as acetonitrile and N,N-dimethylformamide is hardly as dramatic. Measured refractive indices provide a means for converting Onsager to Born polarity, which is essential for analyzing medium effects on electrochemical trends. This study demonstrates a robust optical means, encompassing steady-state spectroscopy and refractometry, for characterizing solution properties important for charge-transfer science and electrochemistry. [ABSTRACT FROM AUTHOR]

In this article, goniometric methods for measuring the refractive index of optically transparent materials are discussed, and a modified method for measuring the refractive index of triangular prisms is proposed. A modified constant deviation method for measuring the refractive index was proposed in the previous study [1] that did not require refractive angle measurement of the prism and simplified the measurement process; however, its implementation required low-intensity radiation reflected from the input face of the prism, which created difficulties in processing signals from a photoelectric receiver and can increase measurement error. In this study, this problem was eliminated with the usage of two fixed mirrors to obtain the reflection of the refracted beam and determine the initial position of the prism, and the refractive index of the prism material was calculated from the solution of a system of equations. This approach avoids the use of radiation reflected from the prism faces, which helped in increasing the accuracy by automating the measurement process. Herein, the results of an experimental study of a triangular prism made of optical glass using the proposed modified prism method are compared with the values obtained using the least deviation method, which has the highest accuracy in determining the refractive index. The proposed method can be used to study triangular prisms made of optically transparent materials as well as optically transparent liquids poured in a hollow triangular prism. [ABSTRACT FROM AUTHOR]

Goniometric methods for measurement of the refractive index of optically transparent materials are considered. A modified constant deviation method is proposed for measurement of the refractive index of a trihedral prism. The proposed modified method does not require measurement of the refractive angle of the prism, which simplifies the measurement process compared to the widely used methods of minimum deviation (the Fraunhofer method) and autocollimation (the Littrow–Abbe method). To implement the method, a goniometric system was used, designed to measure angles formed by flat surfaces of objects. In order to obtain a reflection of the refracted ray, a fixed mirror was placed in its path, and the refractive index of the prism material was calculated from the solution of a system of equations. Results are presented for an experimental study of a triangular prism made of optical glass using the proposed method, and they are compared with results obtained using the method of minimum deviation. The proposed method of constant deviation can be used to study trihedral prisms made of optically transparent materials, as well as liquid optically transparent substances placed in a hollow trihedral prism. [ABSTRACT FROM AUTHOR]

Lab-on-a-chip systems are currently one of the most promising areas in the development of ultra-compact sensor systems, used primarily for gas and liquid analysis to determine the concentration of impurities. Integrated photonics is an ideal basis for designing "lab-on-a-chip" systems, advantageous for its compactness, energy efficiency, and low cost in mass production. This paper presents a solution for "lab-on-a-chip" device realization, consisting of a sensor and an interrogator based on a silicon-on-insulator (SOI) integrated photonics platform. The sensor function is performed by an all-pass microring resonator (MRR), installed as a notch filter in the feedback circuit of an optoelectronic oscillator based on an electro-optic phase modulator. This structure realizes the frequency interrogation of the sensor with high accuracy and speed using a conventional single-mode laser source. The system sensitivity for the considered gases is 13,000 GHz/RIU. The results show that the use of frequency interrogation makes it possible to increase the intrinsic LoD by five orders. The proposed solution opens an opportunity for fully integrated implementation of a photonic "laboratory-on-a-chip" unit. [ABSTRACT FROM AUTHOR]

Mutations in GPR179 are one of the most common causes of autosomal recessive complete congenital stationary night blindness (cCSNB). This retinal disease is characterized in patients by impaired dim and night vision, associated with other ocular symptoms, including high myopia. cCSNB is caused by a complete loss of signal transmission from photoreceptors to ON-bipolar cells. In this study, we hypothesized that the lack of Gpr179 and the subsequent impaired ON-pathway could lead to myopic features in a mouse model of cCSNB. Using ultra performance liquid chromatography, we show that adult Gpr179−/− mice have a significant decrease in both retinal dopamine and 3,4-dihydroxyphenylacetic acid, compared to Gpr179+/+ mice. This alteration of the dopaminergic system is thought to be correlated with an increased susceptibility to lens-induced myopia but does not affect the natural refractive development. Altogether, our data added a novel myopia model, which could be used to identify therapeutic interventions. [ABSTRACT FROM AUTHOR]

Honey is a naturally occurring material made by bees from the sweet, fragrant nectar of flowers. More than 200 substances have been identified in honey, the majority of which are sugars and water. Certain physical characteristics of honey, such as crystallization and viscosity, are substantially affected by moisture. The honey may be stored for a longer period of time because of the low water content, which shields it from microbial activity. Honey from around Pozarevac, the place in Serbia with the largest production of honey, was controlled. A refractometer from A. KRÜSS Optronic GmbH was used for this research. In the period from 2019 to 2021, 99 samples of acacia honey and 114 samples of meadow honey were analyzed. The average values of water percentage in the indicated period in both types of honey were between 16 % and 17 %. Based on this research, it can be concluded that the percentage of water in acacia and meadow honey was below the maximum allowed values according to national and European regulations. Below 17 % water content, honey fermentation is inhibited. Honey with a water percentage above 17 % is sensitive to fermentation, while honey with a water content above 19 % is extremely vulnerable. [ABSTRACT FROM AUTHOR]

The design of a refractometric sensing system for liquids analysis with a sensor and the scheme for its intensity interrogation combined on a single photonic integrated circuit (PIC) is proposed. A racetrack microring resonator with a channel for the analyzed liquid formed on the top is used as a sensor, and another microring resonator with a lower Q-factor is utilized to detect the change in the resonant wavelength of the sensor. As a measurement result, the optical power at its drop port is detected in comparison with the sum of the powers at the through and drop ports. Simulations showed the possibility of registering a change in the analyte refractive index with a sensitivity of 110 nm per refractive index unit. The proposed scheme was analyzed with a broadband source, as well as a source based on an optoelectronic oscillator using an optical phase modulator. The second case showed the fundamental possibility of implementing an intensity interrogator on a PIC using an external typical single-mode laser as a source. Meanwhile, additional simulations demonstrated an increased system sensitivity compared to the conventional interrogation scheme with a broadband or tunable light source. The proposed approach provides the opportunity to increase the integration level of a sensing device, significantly reducing its cost, power consumption, and dimensions. [ABSTRACT FROM AUTHOR]

Global navigation satellite system (GNSS) refractometry enables automated and continuous in situ snow water equivalent (SWE) observations. Such accurate and reliable in situ data are needed for calibration and validation of remote sensing data and could enhance snow hydrological monitoring and modeling. In contrast to previous studies which relied on post-processing with the highly sophisticated Bernese GNSS processing software, the feasibility of in situ SWE determination in post-processing and (near) real time using the open-source GNSS processing software RTKLIB and GNSS refractometry based on the biased coordinate Up component is investigated here. Available GNSS observations from a fixed, high-end GNSS refractometry snow monitoring setup in the Swiss Alps are reprocessed for the season 2016/17 to investigate the applicability of RTKLIB in post-processing. A fixed, low-cost setup provides continuous SWE estimates in near real time at a low cost for the complete 2021/22 season. Additionally, a mobile, (near) real-time and low-cost setup was designed and evaluated in March 2020. The fixed and mobile multi-frequency GNSS setups demonstrate the feasibility of (near) real-time SWE estimation using GNSS refractometry. Compared to state-of-the-art manual SWE observations, a mean relative bias below 5% is achieved for (near) real-time and post-processed SWE estimation using RTKLIB. [ABSTRACT FROM AUTHOR]

A procedure is presented which calibrates a wavelength/refractive-index tracker, so that it can compensate for the absolute refractive index of air within 3 × 10−8 ⋅ n. The procedure employs ultrahigh-purity helium and argon as reference gases of known n (p , T) to deduce the two unknown parameters in the working equation of the tracker: gas pathlength and pressure-induced distortion error. The performance of the gas calibration procedure is evaluated by comparing the corrected tracker against a master refractometer based on a Fabry–Perot cavity in nitrogen, a third reference gas of known n (p , T). In nitrogen, the calibrated trackers demonstrate accuracy at the level of 4 × 10−9 ⋅ n. Testing in a fourth reference gas—water vapor—reveals that the working equation of the trackers must include a third unknown parameter: an end-effect caused by a moisture-dependence of the reflection phase-shift. Correcting for this moisture-related error represents the largest contribution to measurement uncertainty, and explains why performance of the calibrated trackers is an order-of-magnitude worse in moist air than in pure gas. In air, the Fabry–Perot cavity-based refractometer performs within 5 × 10−9 ⋅ n , but is not a commercially-available device. • A gas-based calibration procedure enables commercial wavelength/refractive-index trackers to be absolute at point-of-use. • Testing of the commercial devices against a master refractometer in dry gas and in water vapor reveal the performance limits. • Measurement of water vapor refractivity is compared with a recent ab initio calculation of the static dipole polarizability. • Comparison to an Edlen equation reveals that a formulation due to Bönsch and Potulski is essentially exact at 633 nm and NTP. [ABSTRACT FROM AUTHOR]

Optofluidic sensors integrate photonics with micro/nanofluidics to realize compact devices for the label‐free detection of molecules and the real‐time monitoring of dynamic surface binding events with high specificity, ultrahigh sensitivity, low detection limit, and multiplexing capability. Nanophotonic structures composed of metallic and/or dielectric building blocks excel at focusing light into ultrasmall volumes, creating enhanced electromagnetic near‐fields ideal for amplifying the molecular signal readout. Furthermore, fluidic control on small length scales enables precise tailoring of the spatial overlap between the electromagnetic hotspots and the analytes, boosting light‐matter interaction, and can be utilized to integrate advanced functionalities for the pre‐treatment of samples in real‐world‐use cases, such as purification, separation, or dilution. In this review, the authors highlight current trends in nanophotonics‐enabled optofluidic biosensors for applications in the life sciences while providing a detailed perspective on how these approaches can synergistically amplify the optical signal readout and achieve real‐time dynamic monitoring, which is crucial in biomedical assays and clinical diagnostics. [ABSTRACT FROM AUTHOR]

It is critical that bovine maternal colostrum is fed to newborn calves during their first hours of life. Colostrum is the secretion a cow produces after mammary involution that is rich in various nutrients. In addition to the nutritive value for newborn calves, immunoglobulins are of interest due to their role in developing the naïve immune system of calves at birth. The process by which a calf acquires immunity via absorption of immunoglobulins is defined as passive immunity. When calves consume an adequate amount of immunoglobulins, they are classified as having successful passive immunity (SPI). In contrast, if they are deprived of adequate colostrum, they are considered to have had a failure of transfer of passive immunity (FPI). Transfer of passive immunity is assessed by measuring serum IgG concentrations at 24 to 48 h of age. The major factors that influence whether a calf has SPI or FPI are colostrum IgG concentration, quantity fed, and age of calf at colostrum feeding. Monitoring apparent efficiency of immunoglobulin absorption in calves is often recommended to evaluate overall colostrum management practices. Serum IgG analyses can be determined with direct (radial immunodiffusion) or indirect (refractometry) methods and used to assess SPI or FPI prevalence. [Display omitted] [ABSTRACT FROM AUTHOR]

The determination of salinity values from SI traceable densimetry and refractometry measurement results enable SI traceability of the former. In this work, a short study of the metrological compatibility of salinity determinations via these two methods for sodium chloride in ultrapure water solutions and two different standard seawaters (OSIL and ERM) solutions, in the [35.0; 215.0] g kg−1 interval, is presented. It evidenced the metrological compatibility of the salinity determinations in the referred interval. The largest salinity values enabled to test the matrix effect upon the determinations and concluded the preferable use of densimetry technique, when occurring. [ABSTRACT FROM AUTHOR]

Critical angle refractometry is an established technique for determining the refractive index of liquids and solids. For transparent samples, the critical angle refractometry precision is limited by incidence angle resolution. For lossy samples, the precision is also affected by reflectance measurement error. In the present study, it is demonstarted that reflectance error can be practically eliminated, provided that the sample's extinction coefficient is a priori known with sufficient accuracy (typically, better than 5%) through an independent measurement. Then, critical angle refractometry can be as precise with lossy media as with transparent ones. [ABSTRACT FROM AUTHOR]

To describe the medium-term ophthalmological findings in patients recovering from COVID-19. Patients recovered from the acute phase of COVID-19 underwent a complete ophthalmological evaluation, including presenting and best-corrected visual acuity (BCVA), refractometry, biomicroscopy, tonometry, break-up time and Schirmer tests, indirect ophthalmoscopy, color fundus picture, and retinal architecture evaluation using optical coherence tomography. Socio-demographic data and personal medical history were also collected. According to the severity of systemic manifestations, patients were classified into mild-to-moderate, severe, and critical. Sixty-four patients (128 eyes) were evaluated 82 ± 36.4 days after the onset of COVID's symptoms. The mean ± SD duration of hospitalization was 15.0 ± 10.7 days. Seven patients (10.9%) had mild-to-moderate, 33 (51.5%) severe, and 24 (37.5%) critical disease. Median [interquartile ranges (IQR)] presenting visual acuity was 0.1 (0–0.2) and BCVA 0 (0–0.1). Anterior segment biomicroscopy was unremarkable, except for dry eye disease, verified in 10.9% of them. The mean ± SD intraocular pressure (IOP) in critical group (14.16 ± 1.88 mmHg) was significantly higher than in severe group (12.51 ± 2.40 mmHg), both in the right (p 0.02) and left eyes (p 0.038). Among all, 15.6% had diabetic retinopathy, and two patients presented with discrete white-yellowish dots in the posterior pole, leading to hyporreflective changes at retinal pigment epithelium level, outer segment, and ellipsoid layers. The present study identified higher IOP among critical cases, when compared to severe cases, and discrete outer retina changes 80 days after COVID-19 infection. No sign of uveitis was found. [ABSTRACT FROM AUTHOR]

The dependences of the adsorption and refractometric parameters of a polymer composition containing Rhodamine B in the molecular state on the concentration of lead atoms are studied. These dependences are used as a basis of an express-method of determining the concentration of lead ions in water, the sensitivity of which is shown to be as high as 0.001 mg/L, which is below the maximum permissible concentration. The use of the water-insoluble dye as a material sensitive to lead ions shows the possibility of developing a stable sensor based on the effect under study. The use of the frustrated total internal reflection method for determining the lead concentration by the aforementioned optical parameters is considered. [ABSTRACT FROM AUTHOR]

An interference microscopy-based method for measuring the refractive index of microscopic objects is considered. It is shown that of special interest is the analysis of the dispersion of the refractive index of small objects of biological fluids, which can make it possible to separate fluctuations of the size and the refractive index of the object in studying living cells by methods of phase microscopy. A method for measuring the dispersion of the refractive index of microscopic volumes of fluids using the MIA-1D automated interference microscope and a measuring cell with a microwell is described. An algorithm for processing the obtained images with the aim of calculating the refractive index is presented. The measurement results for the dispersion of the refractive index of bovine serum albumin are given. It is shown that the proposed method allows one to measure the refractive index of fluids in microscopic volumes up to four or five decimal places. [ABSTRACT FROM AUTHOR]

The study focused on the production of wine from date palm fruits (Phoenix dactylifera L.) using a strain of yeast isolated from selected Nigerian locally fermented beverages ('pito', 'brukutu' and palm wine). Seven (7) distinct yeasts were isolated and identified using cultural, microscopy and biochemical tests (temperature tolerance, flocculation, ethanol tolerance, H2S production and killer toxin production and the ability to assimilate and ferment sugars. The yeast isolates were screened using refractometric and spectrophotometric methods to select the isolate with the best ability for wine production. This isolate was molecularly characterized, grown in 1 L of potatoes dextrose broth, freeze dried and used for wine production. The population of yeast, bacteria and the physicochemical analysis of the must were monitored during fermentation. Populations of bacteria in the wine were assessed by standard pour plate count. The proximate content and physicochemical properties of the produced wine before and after ageing, as well as the sensorial quality of the produced wine was determined. All the yeast isolates possessed the ability to flocculate, tolerate ethanol concentration of between 5 and 20% and temperature range of 30–45 °C, produced low concentration of H2S and does not produce killer toxins. A palm wine isolate, identified as Saccharomyces cerevisiae X01 was selected as the best isolate with the most ability for wine production. The total yeast count increases as the period of fermentation progressed while the total viable bacterial count reduced as the fermentation period progressed. There was a significant difference (P < 0.05) in the physicochemical properties of the must during fermentation. At the end of the fermentation, the produced wine had 5.22% and 4.86% ethanol content for S. cerevisiae QA23 and S. cerevisiae X01 respectively. There was no significant difference (P > 0.05) between the proximate and physicochemical compositions of the produced wine before and after ageing using Saccharomyces cerevisiae X01 when compared to the control S. cerevisiae QA23. This study revealed that the Nigerian locally sourced S. cerevisiae X01 can be used as an alternative substrate for industrial scale production of wine with a mild alcoholic content. [ABSTRACT FROM AUTHOR]

Besides water, raw methanol produced from steel mill gases within the Carbon2Chem® project contains dissolved carbon dioxide. Refractometry and densimetry were investigated as analysis methods to analyze raw methanol samples quickly and reliably. To verify existing calibration curves, a set of standard solutions from pure chemicals was produced. Experimental results differed significantly from published refractive index data, especially in the range of high methanol weight fractions, which are of particular interest for the Carbon2Chem® project. [ABSTRACT FROM AUTHOR]

We present a refractometric sensor realized as a stack of metallic gratings with subwavelength features and embedded within a low-index dielectric medium. Light is strongly confined through funneling mechanisms and excites resonances that sense the analyte medium. Two terminations of the structure are compared. One of them has a dielectric medium in contact with the analyte and exploits the selective spectral transmission of the structure. The other design has a metallic continuous layer that generates surface plasmon resonances at the metal/analyte interface. Both designs respond with narrow spectral features that are sensible to the change in the refractive index of the analyte and can be used for sensing biomedical samples. [ABSTRACT FROM AUTHOR]

Direct optical detection has proven to be a highly interesting tool in biomolecular interaction analysis to be used in drug discovery, ligand/receptor interactions, environmental analysis, clinical diagnostics, screening of large data volumes in immunology, cancer therapy, or personalized medicine. In this review, the fundamental optical principles and applications are reviewed. Devices are based on concepts such as refractometry, evanescent field, waveguides modes, reflectometry, resonance and/or interference. They are realized in ring resonators; prism couplers; surface plasmon resonance; resonant mirror; Bragg grating; grating couplers; photonic crystals, Mach-Zehnder, Young, Hartman interferometers; backscattering; ellipsometry; or reflectance interferometry. The physical theories of various optical principles have already been reviewed in detail elsewhere and are therefore only cited. This review provides an overall survey on the application of these methods in direct optical biosensing. The "historical" development of the main principles is given to understand the various, and sometimes only slightly modified variations published as "new" methods or the use of a new acronym and commercialization by different companies. Improvement of optics is only one way to increase the quality of biosensors. Additional essential aspects are the surface modification of transducers, immobilization strategies, selection of recognition elements, the influence of non-specific interaction, selectivity, and sensitivity. Furthermore, papers use for reporting minimal amounts of detectable analyte terms such as value of mass, moles, grams, or mol/L which are difficult to compare. Both these essential aspects (i.e., biochemistry and the presentation of LOD values) can be discussed only in brief (but references are provided) in order to prevent the paper from becoming too long. The review will concentrate on a comparison of the optical methods, their application, and the resulting bioanalytical quality. [ABSTRACT FROM AUTHOR]

Perovskite solar cells are currently considered a promising technology for solar energy harvesting. Their capability to deliver an electrical signal when illuminated can sense changes in environmental parameters. We have numerically analyzed the variation of the current delivered by a perovskite cell as a function of the index of refraction of air, that is in contact with the front surface of the cell. This calculation identifies which geometrical and material structures enhance this behavior. After replacing the top transparent electrode of a solar cell by an optimized subwavelength metallic grating, we find a large variation in the responsivity of the cell with respect to the change in the index of refraction of the surrounding medium. Such a refractometric sensor can be interrogated electronically, avoiding the cumbersome set-ups of spectral or angular interrogation methods. We present an adaptation of the performance parameters of refractometric sensors (sensitivity and figure of merit) to the case of opto-electronic interrogation methods. The values of sensitivity and Figure of Merit are promising for the development of refractometric perovskite-based sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Analyzing solubility for compound set requires 4 chemical techniques but 1 physical. • Fewer process steps, including compound-specific calibration and sampling. • Solubility experiment duration reduced from appr. 3 days to less than 3 h. In this work, the optical imaging based single particle analysis (SPA) and the gold standard shake-flask (SF) solubility methods are compared. We show that to analyze pharmaceutical compounds spanning 7 log units in solubility and a diverse chemical space with limited resources, several analytical techniques are required (HPLC-UV, LC-MS, refractometry and UV–Vis spectrometry), whereas solely the SPA method is able to analyze all the same compounds. SPA experiments take only minutes, while for SF, it may take days to reach thermodynamic equilibration. This decreases the time span needed for the solubility experiment from initial preparations to obtaining the result from roughly three days to less than three hours. The optimal particle size for SPA ranges from approximately one to hundreds of microns. Challenges include measuring large particles, very fast dissolving compounds and handling small sample sizes. Inherent exclusion of density from the SPA measurement is a potential source of error for compounds with very low or high density values. The average relative difference of 37 % between the two methods is very good in the realm of solubility, where 400 % interlaboratory reproducibility can be expected. [ABSTRACT FROM AUTHOR]

• Polymeric optical adhesive NOA65 functionalized by additive ionic liquid (IL). • The refractive index and transmission of doped NOA65 uninfluenced by IL addition. • Dielectric characteristics in relation to IL doping concentration and temperature. • Activation energy of DC electrical conductivity reduced by doping IL into NOA65. • (Pseudo-)dielectric heating behaviors caused by (pseudo-)dielectric relaxation. Conductive polymers that exhibit exceptional electrical conductivity have garnered significant interests in recent decades, disclosing remarkable potentials across a broad range of industries. In this study we investigated a series of Norland UV-curable optical adhesive (NOA65) doped with ionic liquid (1-hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide) at various concentrations from 0 wt% to 2.0 wt%. The refractive indices of the doped prepolymers and photopolymerized NOA65 were examined by Abbe refractometry with four wavelength filters at distinct temperatures. Moreover, the transmission spectra, frequency-dependent complex dielectric and conductivity properties of the composites were explored in comparison with their pristine precursor and photopolymer. Interestingly, by applying an alternating electric field within a specific frequency range, we found that these samples can undergo unique dielectric relaxation, and thus give rise to the observed heating effect. Our preliminary results demonstrate that the conductivity of the proposed polymer composites is significantly higher than that of the undoped counterpart, whereas the refractive index, dispersion, and transmission remain virtually unchanged, revealing great promise for real applications in optoelectronic technology. [ABSTRACT FROM AUTHOR]

Almost 75 years after implementing the industrial ethanol fractionation process, based on the pioneering work of Edwin J. Cohn's research group, this niche biotechnology process has not lost its importance in helping to supply patients with life-saving biotherapies. Clearly, the focus has shifted from albumin, which was first used, to the indispensable immunoglobulin preparations produced for the effective, long-term treatment of patients suffering from immunodeficiencies. In addition, the widespread and safe therapeutic use of immunoglobulins has paved the way for the development of monoclonal antibodies, now used not only for the treatment of various autoimmune diseases, but also for cancer treatment. The Cohn fractionation process, based on the different solubilities of plasma proteins, depends on the five parameters of ethanol concentration, pH, temperature, protein, and salt concentration, which are the basis of this development. Ethanol concentration can clearly be considered an essential critical parameter for this process. Therefore, it is surprising that even after the advent of process analytical technology, there is still no fast, precise, and accurate procedure at hand to determine the alcohol content of Cohn fractionation intermediates. In this paper, we will describe the implementation of an old methodology for a new purpose, which is designed to close this gap. [ABSTRACT FROM AUTHOR]

To determine if low molecular weight synthetic colloid fluids administered to dogs interfere with refractometric estimates of total plasma protein (TPPr) and urine osmolality (UOsm). Experimental study. Eighteen healthy Greyhound dogs. Anaesthetized Greyhounds subjected to haemorrhage for 60 minutes were given 80 mL kg–1 of Plasma-Lyte 148 (CRYST), or 20 mL kg–1 of hydroxyethyl starch 130/0.4 (HES) or succinylated gelatine (GELO) (n = 6 per group) intravenously over 20 minutes. Refractometric (TPPr) and biuret total plasma protein (TPPb) were measured before haemorrhage (Baseline), at end of shock (Shock), immediately (T20), then 40 minutes (T60), 100 minutes (T120) and 160 minutes (T180) after fluid administration. Urine specific gravity (USG) and UOsm were measured at all time points except T20. Estimated UOsm (eUOsm) was calculated from USG. Bias and limits of agreement (LOA) for TPPr versus TPPb, and eUOsm versus UOsm were calculated at each time point. For dogs given CRYST and GELO, median TPPr and TPPb decreased in parallel, with a small consistent TPP bias (CRYST range of bias, 0.38−0.67 g dL–1; GELO range of bias, 0.42−0.58 g dL–1). Dogs given HES showed divergence between median TPPr and TPPb after T20, with a peak bias at T20 of 1.62 g dL–1 (LOA 1.29−1.95). Dogs given HES and GELO had markedly increased USG [HES peak median USG at T180 of 1.119 (Q1−Q3 1.103−1.122); GELO peak median USG at T120 of 1.114 (Q1−Q3 1.082−1.119)], with large increases in bias between eUOsm and UOsm [HES peak bias at T60 of 2995 mOsm kg–1 (LOA 2032−3958 mOsm kg–1); GELO peak bias at T120 of 2465 mOsm kg–1 (LOA 940−3990 mOsm kg–1)]. Administration of HES and GELO to dogs with haemorrhagic shock interferes with refractometric measurements for at least 3 hours after administration. [ABSTRACT FROM AUTHOR]

Under field conditions, during 2016, were studied 15 cultivars of tomatoes. When the fruit reached commercial maturity, the following quality indices were determined: water content and total dry substance (gravimetric method), soluble dry substance (refractometric method), titratable acidity (titrimetric method), total carbohydrates (Fehling Soxhlet method) and vitamin C (iodometric method). The best results on the quality of tomato fruits were obtained with the following cultivars: St. Pierre (7.33% total dry substance, 4.2% soluble dry substance, 0.67% acidity, 3.50% carbohydrate and 19.36 mg vitamin C), Caspar F1 (5.98% total dry substance, 3.8% soluble dry substance, 0.60% acidity, 3.20% carbohydrate and 21.12 mg vitamin C), Mirsini F1 (5.68% total dry substance, 4.0% soluble dry substance, 0.64% acidity, 3.30% carbohydrate and 21.12 mg vitamin C), Heintz (5.67% total dry substance, 3.7% soluble dry substance, 0.80% acidity, 3.10% carbohydrate and 24.64 mg vitamin C) and Darsirius (5.21% total dry substance, 3.9% soluble dry substance, 0.69% acidity, 3.20% carbohydrate and 19.36 mg vitamin C). [ABSTRACT FROM AUTHOR]

Efficient production in the sugar industry requires the use of cultivars with high sucrose content. The objective of the work was to characterize the agronomic response of 70 new sugarcane cultivars (Saccharum spp.) introduced in the clonal stage of selection and initial period of the sugar harvest in the Ofelina sugarmill (La Estrella SA, CALESA, Republic of Panama). The characters evaluated were the refractometric brix, number of stems m-1, t cane ha-1, incidence of harmful agents, flowering, thickness and height of the stem. A randomized block design with three repetitions was used. Analysis of random effect variances was performed to estimate the genetic and environmental components, fixed and to establish the differences among cultivars. With the individuals selected, a cluster analysis was performed. The difference among the groups formed was verified with another analysis of variances of fixed effects and the Tukey test. Inheritance, Genetic Coefficient of Variation (CGV) and standard error for each variable evaluated were also estimated. It was shown that the genetic variance was greater than that of the error, except in the diameter, which confirms the importance of the genetic component at this stage of selection. The CGV was higher for agricultural performance variables in the 2011 and 2010 selection, the Brix was comparable to the height and higher than the diameter. It were selected 38 new cultivars that were recommended for the final stage of selection. [ABSTRACT FROM AUTHOR]

Abstract Size-exclusion chromatography (SEC) with on-line static light scattering, specifically multi-angle static light scattering (MALS), and differential refractometry (DRI) detection remains the premier method by which to determine absolute, calibrant-independent molar masses of polymers. The method is restricted to the use of either neat solvents or solvents with a small amount of additive. In mixed solvents, preferential solvation (i.e., the enrichment, within the solvated volume of the polymer in solution, of one solvent over the other as compared to the solvent ratio outside said volume) leads to errors in the areas of the MALS and DRI chromatograms, as the solvent baseline does not accurately represent the solvent contribution to these detectors' peaks. A seemingly trivial way by which to overcome this problem is through the use of an isorefractive solvent pair. This "trivial" solution is complicated by the fact that the solvents in the pair must be miscible with each other in all proportions; the individual solvents as well as the mix must be able to fully dissolve the analyte; the solvents must possess sufficient optical contrast with the solution so as to generate an adequate detector signal; the solvent mix must be compatible with the chromatographic stationary phase, such that enthalpic contributions to the separation are minimal and analyte recovery from the columns is quantitative; and the difference in the Rayleigh factors of the solvents can be ignored. Herein, we present the analysis of narrow dispersity polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples, across a four-fold range in molar mass, using SEC/MALS/DRI in a mix of tetrahydrofuran (THF) and methyl isoamyl ketone (MIAK), solvents which are shown to be isorefractive with each other at the temperature and wavelength of the experiments. Molar mass averages and dispersities are demonstrated to be statistically independent of solvent composition and to correspond well to the values in neat THF. The experiments were augmented by the use of on- and off-line quasi-elastic light scattering and of off-line MALS and DRI, to study the effect of solvent composition on polymer size in solution and on dilute solution thermodynamics. Additionally, 1H nuclear magnetic resonance spectroscopy was used to study the effect of tacticity on the insolubility of PMMA100 in 100% MIAK. We believe this constitutes the first example of obtaining accurate molar masses of polymers by SEC/MALS/DRI employing mixed solvents. The value of these experiments to other forms of macromolecular liquid chromatographic separations is also noted. Graphical abstract Image 1 Highlights • Absolute molar mass determination for polymers in mixed solvents. • Determination is normally compromised by selective solvation of polymer coil. • Selective solvation can be circumvented by use of isorefractive solvent pair. • Size-exclusion chromatography can successfully address experimental issues. • On-line light scattering and refractometry detection are needed. [ABSTRACT FROM AUTHOR]

Antecedentes: los terneros nacen desprovistos de inmunoglobulinas (Ig) en el suero sanguíneo‚ lo que los hace completamente dependientes del calostro‚ lo que se denomina transferencia de inmunidad pasiva. Objetivo: analizar la transferencia de inmunidad pasiva mediante la medición del número de inmunoglobulinas G (IgG) y la concentración de proteína sérica total (PST) utilizando refractometría en neonatos que recibieron leche de un banco de calostro. Métodos: 48 neonatos fueron incluidos en el estudio. Se tomaron muestras del calostro del primer ordeño de vacas recién paridas en la Granja Experimental Betania de la compañía Solla S.A‚ ubicada en Santa Rosa de Osos‚ Antioquia. El calostro del primer ordeño fue evaluado a través del método del calostrómetro que mide el nivel de IgG en el calostro. Calostros con niveles altos de IgG fueron incluidos en el banco de calostro de la granja. Evaluación de la concentración de grados BRIX en el suero sanguíneo de las crías dos horas posteriores al suministro del calostro fue realizada siguiendo el método del refractómetro. Los datos fueron analizados en el software R (R Core Team. (2020) mediante análisis de varianza (ANOVA) y modelo de regresión lineal permitiendo analizar las variables respuesta en función de factores como: sexo‚ hora nacimiento y consumo de calostro. Resultados: se encontró una correlación positiva (0‚31) entre el porcentaje de refractometría y número de IG indicando que un aumento en una unidad de IgG repercute en una mejor trasferencia de inmunidad pasiva. El ANOVA para la variable IgG encontró que el sexo de las crías y el horario de nacimiento tuvieron un efecto significativo (p < 0,005) en la transferencia de inmunidad pasiva. Las crías hembras mostraron una mejor transferencia‚ y las crías nacidas durante el día tuvieron una respuesta inmunitaria más adecuada. La variable refractometría no encontró una significancia estadística Conclusión: la cantidad‚ calidad y hora de consumo del calostro (día o noche) repercute en la respuesta inmunitaria del animal. Los resultados obtenidos proporcionan información sobre el manejo del neonato y el programa de encalostrado en la granja Betania. [ABSTRACT FROM AUTHOR]

All-dielectric metasurfaces supporting resonant quasi-bound states in the continuum (qBIC) offer an ideal platform for various applications relying on intense light–matter interaction in highly localized and enhanced fields. Here, we propose a dielectric metasurface composed of hollow GaP nanocuboid quadrumers periodically arranged on a silica substrate. The metasurface supports a qBIC resonant mode with an antiferroelectric field configuration, which is very robust to large perturbations of the cuboid structure thanks to its perpendicular electric dipole field profile. The perturbed quadrumer arrangement retains C 4 v symmetry, thus allowing for polarization-independent optical response for normally incident planewaves. In addition, the resonant mode dispersion is investigated, revealing interesting features, such as low birefringence along the Γ M contour of the Brillouin zone and very low dispersion for the TM polarization along the Γ X direction. The metasurface is designed to resonate close to 785 nm , which is highly relevant for Raman spectroscopy, leveraging the strong field enhancement at the interface with the overlayer material. Moreover, its performance as a bulk refractometric sensor is discussed. The proposed dielectric metasurface is promising for emerging photonic phenomena where strong light–matter interaction plays a key role. [Display omitted] • Polarization-independent GaP metasurfaces with robust quasi-BIC resonances. • Very low dispersion for the TM polarization in the Γ X direction of the Brillouin zone. • High sensitivity for bulk refractometry of an overlayer analyte. • Strong near-field confinement for quasi-BIC enhanced Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Dynamic optical sensors, as those based on the reflectivity of isotropic dielectrical interfaces, can be useful for measuring small changes in the refractive index of fluid media. Exact and approximated explicit formulas for their sensitivity are developed. These expressions clarify the influence of each of the constructive parameters of the device, both in partial and in total reflection. It is analytically found that sensitivities are always greater when the angle of incidence approaches the angle of total reflection. It is also demonstrated that close to the critical angle for both types of reflection, the sensitivity of the p mode is greater than that of the s mode. [ABSTRACT FROM AUTHOR]

Highlights • Optical pressure standard based on the refractive index measurement by a multi-reflection homodyne interferometer. • Absolute length measurement of the unbalance of the interferometer. • Pressure standard in the range between 1 kPa and 120 kPa. • Comparison between optical pressure standard and a calibrated barometer. Abstract A novel pressure standard based on optical interferometry has been realized. The paper presents a preliminary achievement of the system, in which the standard pressure between 1 kPa and 120 kPa is obtained through the measurement of the refractive index of a gas. The response of the optical system has been initially evaluated measuring its sensitivity for nitrogen and air, in terms of the ratio between a pressure variation and the number of detected interferometric fringes. Afterwards, the interferometer has been geometrical characterized in order to perform an absolute measurement of the refractive index of the gas, allowing an optical measurement of the gas pressure. The following step has been to compare the results of a series of measurements obtained with the optical system with a reference pressure standard at 120 kPa. Finally, the standard has been compared with two capacitance diaphragm gauges in the range between 1 kPa and 120 kPa. The device has a relative standard uncertainty equal to 170 ppm at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Highlights • Structurally-modified tapered optical fiber sensor for detection of liquids studied. • Described structural modification of the sensor surface for enhanced sensitivity. • Sensors' response curve can be shifted by structural modification. • Long term tests validated time-stability of structurally-modified sensors. Abstract We present an improvement of tapered optical fiber (TOF) sensor's response for the detection of liquids, which is achieved by TOF surface structural modification. Our TOF sensors utilize the refractometric principle with enhanced evanescent-wave overlap due to the wavelength of 1550 nm and TOF waist diameters of 4–6 μm. The structural modification is achieved by long-term TOF exposition to hygroscopic liquid analytes and ambient atmosphere. To analyze the structural modification process, long-term as well as proof-of-principle tests have been carried out to evaluate TOF sensors stability in terms of sensitivity and resolution. Maximum sensitivity of over 2100 dB/RIU has been reached when TOF is used to detect a liquid analyte with refractive index of 1.415. Increase of more than 1400 dB/RIU is attributed to the enhanced sensitivity. Sample TOF sensors were then linearly calibrated and have been tested in more than one year-long continuous measurement campaign. Resolution better than 7 · 10 - 4 for a refractive index range of from 1.405 to 1.425 with working point drift below 2 · 10 - 4 over 12 months period has been achieved. Our results and observations are suitable for reliable, low-cost and application-tailored TOF sensor development. [ABSTRACT FROM AUTHOR]

Highlights • SC-MOF refractometric sensors are suitable for detection of wide range of analytes. • Generalized model can be easily used as a universal tool for SC-MOF sensor design. • Usability of SC-MOF sensors can be predicted based on our generalized model. • SC-MOF sensors exhibit sufficient sensitivity for gasoline-blend quality monitoring. Abstract A generalized model for the detection of liquids within suspended-core microstructured optical fibers has been experimentally and theoretically derived. The sensor detection is based on the refractometric principle of transmission losses due to the overlap of the evanescent field with the liquid analyte. A number of parameters, including fiber core diameter and filling length, have been included in the general model. Specially tailored suspended-core fibers were manufactured with the core diameters within the range of 2.4 μ m to 4.0 μ m. Five selected liquid analytes were used to cover the refractive index range of 1.35 to 1.42. Based on experiments, the characteristics of the parameters of the semi-empirical model have been determined by a genetic algorithm using 283 measurement data sets. The model can be used to design sensors for the detection of liquid analytes as it provides a set of parameters allowing to optimize the sensor's sensitivity for a wide scale of applications. Finally, numerical simulations of the system were carried out by an eigenmode routine to support the results of the generalized model. [ABSTRACT FROM AUTHOR]

Spray mixing of multiple sprays is commonly encountered in industrial applications. In the mixed droplet field, it is of interest while still challenging to quantify the mixing ratios of sprays. This work investigates the measurements of volume mixing ratios of droplet mixtures of two and three sprays with global rainbow refractometry. An algorithm is proposed to simultaneously inverse the size distributions of the sprays and then their volume ratios. The algorithm is validated by simulations, and results show that the volume mixing ratios in mixtures of both two and three sprays can be determined with an accuracy within 5% in the interrogated region from 20% to 70%. The mixing ratios of mixtures of two sprays (water and 30% ethanol, water and ethanol) and three sprays (water, 30% ethanol and ethanol) are also experimentally determined. This technique proposes and demonstrates an effective approach to diagnosing mixtures of multiple sprays. [ABSTRACT FROM AUTHOR]

Highlights • A stable optofluidic Fabry-Pérot (FP) cavity consisting of silicon cylindrical Bragg mirrors combined with a central capillary-tube full of fluids is proposed. • We investigate the properties of these components numerically through the finite-difference time-domain (FDTD) technique with perfectly matched layers (PMLs) absorbing boundary conditions. • A sensitivity of 592 nm per refractive index unit (RIU) with a resolution of less than 10−3 is obtained for liquid refractometry. • For gas refractometry, a sensitivity of 1053 nm per refractive index unit (RIU) with a resolution of 5 × 10−4 is achieved. Abstract In this paper, a stable optofluidic Fabry-Pérot (FP) resonator consisting of silicon cylindrical Bragg mirrors combined with a central capillary-tube is investigated. The cylindrical Bragg mirrors provides an in-plane confinement of light while the central capillary tube full of fluid improves the out-of-plane light confinement. Through the Finite-Difference Time-Domain (FDTD) technique with perfectly matched layers (PMLs) absorbing boundary conditions, a sensitivity of 592 nm per refractive index unit (RIU) with a detection limit (DL) of less than 10−3 RIU is obtained for liquid refractometry. For gas refractometry, a sensitivity of 1053 nm per refractive index unit (RIU) with a detection limit (DL) of 5 × 10−4 RIU is achieved. Such sensitivity is, to our knowledge, the highest ever reported for an RI gas refractometer based on stable optofluidic FP resonator. The proposed device has promising performances which suggest its potential use in future sensing applications. [ABSTRACT FROM AUTHOR]

Silver reduction from its nitrate has been studied in the media of DGEBA-based and aliphatic epoxy resins. It has been found that, under the experimental conditions that were employed, silver ions can be reduced without chemical interaction with the medium only due to photochemical processes. The reduction rate is determined by the rate of dissolution of the initial silver salt in an organic medium and the possibility of the formation of solvates by the system components. Refractometry has been proposed for use in monitoring the kinetics of silver nitrate dissolution in epoxy resins and the formation of silver nanoparticles. Stable dispersions of silver nanoparticles in epoxy resins have been obtained. [ABSTRACT FROM AUTHOR]

We present a study of a novel vacuum arc deposition system composed of a water-cooled aluminum cathode and a hot refractory anode. The plasma of the arc system was diagnosed using a cylindrical electrostatic probe. It was found that the mean electron temperature was ∼2 eV, the plasma density could be varied in the range of 0.5–6 × 1016 m−3, and the ion flux was between 0.06 and 0.35 A m−2. Optical emission spectroscopy measurements showed the presence of emission lines corresponding to Al i and Al ii. The characterization of the coatings showed that the deposition rate varied from 0.8 to 4 nm/s and the surface roughness (Ra) of the films was as low as 25 nm. We demonstrated that it was possible to deposit films with low macroparticle densities, overcoming the principal disadvantage of the vacuum arc process. Measurements of the arc voltage and current were performed as a function of time and the applied magnetic field. The anode temperature was measured using a pyrometer through a ZnS window as a function of time and arc current, and the maximum value was 1800 °C with heating rates of up to 110 °C/s. [ABSTRACT FROM AUTHOR]

A laser refraction method of measurement of the rate of evaporation of a liquid droplet on a horizontal substrate under the conditions of pinning of a contact line is developed. Experimental values of the contact wetting angle in the evaporation process are obtained with the use of refraction images of the droplet. The time dependence of the volume of an evaporated droplet is established based on these values. [ABSTRACT FROM AUTHOR]