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The refractive index (RI) of human milk serum (also known as whey, milk soluble fraction or milk plasma) depends on the individual molecular species dissolved in the serum and their concentrations. Although the human milk serum RI is known to influence milk analysis methods based on light scattering, the RI dependency on human milk serum composition is currently unknown. Therefore, we systematically evaluate how the RI depends on natural variations in macronutrient concentrations in the soluble fraction. We measure RI variations in serum simulating samples with controlled macronutrient concentrations, as well as skimmed and whole fore-, bulk, and hindmilk from 19 donors. For both types of samples, we relate the measured RI to the macronutrient composition. From the serum simulating samples, we observe that the RI depends more on variations in whey protein, than carbohydrate concentrations, while minerals have negligible influence. For all donated samples, the average RI was 1.3470 (range 1.3466–1.3474). Per donor, no significant differences were observed in RI between fore-, bulk, and hindmilk. We conclude that protein and solids-not-fat (i.e., the total contribution of carbohydrates, proteins and minerals present in milk) concentrations are most predictive for human milk serum RI. [ABSTRACT FROM AUTHOR]

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]

This experiment was motivated by the need to understand the impacts of delaying the first colostrum feeding on the prevalence of failed transfer of passive immunity (FTPI). A cohort of 216 kids was stratified into groups based on the colostrum feeding delay postbirth: 0–4 h, 4–8 h, 8–12 h, and 12–16 h. All kids received a single colostrum meal of 300 mL, and blood samples were collected approximately 36 h after feeding. Serum immunoglobulin G (SIgG) was measured using ELISA, and serum total protein (STP) was assessed using the Bradford method and refractometry (STPb and STPr). Statistical methods like Pearson correlations, Bland-Altman plots, and Lin’s concordance coefficient were employed to assess associations and agreements between SIgG, STPb and STPr. Receiver operator characteristic analysis was employed to determine optimal STPb and STPr thresholds for predicting FTPI (SIgG < 12 g/L). Subsequently, areas under the curve, sensitivity, and specificity were examined to assess the accuracy of these thresholds. Our results showed that for each hour’s delay from birth to colostrum intake (up to 16 h), IgG apparent efficiency of absorption (AEA) decreases at an approximate rate of 2.0% per hour, and SIgG decreases at an approximate rate of 1.0 g/L per hour. However, this decline is not constant over time but intensifies progressively with increased feeding delay. Specifically, reductions in IgG AEA were 1.3, 2.9, and 5.9% per hour, and decreases in SIgG were 0.2, 0.3, and 0.7 g per hour for SIgG across the time intervals of 0–4 to 4–8 h, 4–8 to 8–12 h, and 8–12 to 12–16 h, respectively. Additionally, there was an increase in SIgG of 1.2 g/dL but a decrease in IgG AEA of 1.9% for each gram per kg of BW increase in IgG intake. The correlations between SIgG and STPr and STPb were 0.62, and 0.36, respectively. Optimal STPr and STPb thresholds predicting FTPI were determined to be 4.6 and 6.2 g/dL. The prevalence of FTPI, according to SIgG, STPr, and STPb thresholds were 63, 62, and 45%. Overall, STPr showed higher values for key performance metrics (i.e., sensitivity, likelihood ratio of positive tests, overall accuracy, and Youden’s index), indicating better prediction ability than STPb. Our findings corroborate the critical importance of swift colostrum administration, ideally occurring no later than 12 h postbirth. Moreover, our research validates the effectiveness of Brix refractometry as a practical, on-farm method for assessing FTPI in goat kids.

Worldwide polystyrene (PS) production in 2020 was approximately 27 million metric tons, distributed among many nations, making it one of the most heavily imported and exported chemicals. Commercially produced PS usually possesses a broad molar mass distribution, often with a substantial oligomeric component. The latter can significantly affect processing and end-use, in addition to having potentially hazardous health effects and to impacting the polymer's export classification by regulatory agencies. Quantitation of the oligomeric region of polymers by size-exclusion chromatography with concentration-sensitive and/or static light scattering detection is complicated by the non-constancy of the specific refractive index increment (∂n/∂c) in this region, which affects the calculated amount (mass fraction) of oligomer in a polymer, molar mass averages, and related conclusions regarding macromolecular properties. Here, a multi-detector SEC approach including differential refractometry, multi-angle static light scattering, and differential viscometry has been applied to determining the ∂n/∂c of n-butyl terminated styrene oligomers at each degree of polymerization from monomer to hexamer, and also of a hexadecamer. Large changes in this parameter from one degree of polymerization to the next are observed, including but not restricted to the fact that the ∂n/∂c of the monomer is less than half that of PS polymer at identical experimental conditions. As part of this study, the individual effects of injection volume, flow rate, and temperature on chromatographic resolution were examined. Incorporation of the on-line viscometer allowed for accurate determination of the intrinsic viscosity and viscometric radius of the monomer and oligomers. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective: To study vertex-optical distance variation and estimate its impact on manifest refraction. Methods: Prospective study in a private clinic using the Vision-S™ 700 with five forehead positions. Forehead on the third position showed the closest vertex-optical distance of 12mm. Results: Analysis of 52 eyes from 26 patients revealed mean differences in vertex-optical distance of 12.25mm (right eye) and 11.75mm (left eye). A 2mm change in vertex-optical distance resulted in a 0.05D change for a 5D spherical equivalent and 0.20D for a 10D equivalent. Conclusion: Vertex-optical distance varies among patients and is influenced by forehead adjustment. These variations impact refraction accuracy and treatment evaluation. Adjusting the forehead to the third position on the Vision-S™ 700 is recommended.

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.

Microstructured materials that can selectively control the optical properties are crucial for the development of thermal management systems in aerospace and space applications. However, due to the vast design space available for microstructures with varying material, wavelength, and temperature conditions relevant to thermal radiation, the microstructure design optimization becomes a very time-intensive process and with results for specific and limited conditions. Here, we develop a deep neural network to emulate the outputs of finite-difference time-domain simulations (FDTD). The network we show is the foundation of a machine learning based approach to microstructure design optimization for thermal radiation control. Our neural network differentiates materials using discrete inputs derived from the materials' complex refractive index, enabling the model to build relationships between the microtexture's geometry, wavelength, and material. Thus, material selection does not constrain our network and it is capable of accurately extrapolating optical properties for microstructures of materials not included in the training process. Our surrogate deep neural network can synthetically simulate over 1,000,000 distinct combinations of geometry, wavelength, temperature, and material in less than a minute, representing a speed increase of over 8 orders of magnitude compared to typical FDTD simulations. This speed enables us to perform sweeping thermal-optical optimizations rapidly to design advanced passive cooling or heating systems. The deep learning-based approach enables complex thermal and optical studies that would be impossible with conventional simulations and our network design can be used to effectively replace optical simulations for other microstructures.

The paper proposes a modified method for measuring the refractive index of a triangular prism using an autocollimation angle measuring system designed to measure angles formed by flat surfaces of objects. The method involves using a fixed mirror to reflect the refracted beam, measurement of the angles of incidence of the beam on the face of the prism corresponding to the autocollimation positions and calculating the refractive index of the prism material using the solution of a system of equations. The paper presents the experimental study results for a triangular prism made of K8 optical glass using the proposed method, and a comparison of the results with the readings obtained using the State Primary Standard of the Refractive Index Unit GET 138-2021. The proposed method makes it possible to simplify the process of measuring the refractive index since there is no need to measure the angle of deviation of the beam.

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]

Methods for measuring the refractive index of optically transparent dielectric materials are considered. Modified methods based on the methods of minimum deviation and constant deviation are proposed and allow determining the refractive index of triangular prisms with unknown apex angles. In the proposed methods, the angles of light deviation on three faces of the prism are measured, and the refractive index of the material and the prism angles are determined from the solution of a system of equations. To implement the proposed methods, a goniometric system is used. That system was designed to measure angles between the flat surfaces of objects in manual and automated modes. Reference prism samples made of N-SF 1 optical glass, and a hollow prism filled with distilled water are studied. The proposed methods are compared and the measurement error is estimated. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases where the angles of the prism are unknown, or their measurement is associated with technical difficulties.

This article explores the hydration of ions in dilute aqueous solutions of various electrolytes. The researchers studied the hydration numbers of ions in solutions of KCl, KBr, KI, HCl, LiCl, CsCl, and NaCl using a refractometric method. They also investigated the effect of polyethylene glycol (PEG-6000) on the hydration processes in solutions of KCl and KBr. The results showed that the introduction of PEG into the solution decreased the hydration numbers of ions, likely due to the competition between PEG oxygen atoms and ions for interaction with water molecules. This research provides valuable insights into the hydration processes in aqueous solutions of salts and the impact of polymers on these processes. [Extracted from the article]

Methods for measuring the salinity of sea water are considered. The results of an experimental study of samples of common and sea salt solutions with different salinity poured into a hollow trihedral optical glass prism are presented. The light refraction angles are measured with a goniometric system by use of which the minimum deviation method possessing a high accuracy of determining the refractive index is implemented. Using dispersion analysis of experimental results, it is proved that the refractive index of water does not depend on its salt composition. An equation describing the dependence of the refractive index on salinity and temperature for a fixed wavelength is proposed. [ABSTRACT FROM AUTHOR]

The optics of the eye is the key to a functioning visual system. The exact nature of the correlation between ocular optics and eye development is not known because of the paucity of knowledge about the growth of a key optical element, the eye lens. The sophisticated optics of the lens and its gradient of refractive index provide the superior optical quality that the eye needs and which, it is thought, has a major influence on the development of proper visual function. The nature of a gradient refractive index lens, however, renders accurate measurements of its development difficult to make and has been the reason why the influence of lens growth on visual function remains largely unknown. Novel imaging techniques have made it possible to investigate growth of the eye lens in the zebrafish. This study shows measurements using X-ray Talbot interferometry of three-dimensional gradient index profiles in eye lenses of zebrafish from late larval to adult stages. The zebrafish lens shows evidence of a gradient of refractive index from the earliest stages measured and its growth suggests an apparent coincidence between periods of rapid increase in refractive index in the lens nucleus and increased expression of a particular crystallin protein group.

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]

This study investigated the interrelationships between the parameters of density, optical refraction, the volume fraction of ethanol and the total extract, using model solutions and samples of wine materials. The regularities of changes in refractometer readings in the process of alcoholic fermentation have been studied. The functional dependence of the value of the volume fraction of ethanol in the finished wine products on the density and scale of refractometer values has been established. A technique is proposed for controlling the process of alcoholic fermentation of grape must, based on the use of refractometry. Finally, we present an algorithm to calculate the composition (volume fraction of ethanol, mass concentration of the total extract) of the fermentation product from its physical properties (density, refractive index), the coefficient of determination was R2 = 0.975. [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]

Copyright of Arquivos Brasileiros de Oftalmologia is the property of Arquivos Brasileiros de Oftalmologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

We propose a refractometric sensor based on hollow silicon Mie resonators of a toroidal magnetic dipole mode. This mode has a pair of antiparallel electric dipoles perpendicular to the silica substrate; thus, the radiation of the mode is suppressed, resulting in an ultra-narrow reflection peak linewidth of 0.35 nm. In addition, the hollow structure enhances the interaction between the enhanced electric field and the surrounding medium, thus improving the sensitivity. The proposed Mie resonators achieve a sensitivity of 486 nm RIU ^−1 and a figure of merit up to 1389 RIU ^−1 , which are ideal for refractometric sensing.

ABSTRACT: 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.

The present study aims to perform a comparative analysis of vegetable oils and their two-component blends using infrared spectroscopy and refractometry. The study was conducted in Almaty (Kazakhstan) in 2020. Three samples of 44 vegetable oils and their blends made from two components were examined. Fractometry and infrared spectroscopy were used to investigate the properties of blended vegetable oils. To this end, the fatty acid fraction (in percentage), iodine number, and index of refraction (IOR) were calculated. Afterward, the spectrograms obtained for the blends were analyzed. It was found that the difference between the intensities of weak bands and the band expansion of 722 cm−1 indicates greater expressiveness. When low-intensity bands (1653 cm−1) become more distinct due to vibrations of double carbon bonds (C-bonds), the level of unsaturated fatty acids in the blend increases as well.

We present a method to recover absorption and reduced scattering spectra for each layer of a two-layer turbid media from spatial frequency-domain spectroscopy data. We focus on systems in which the thickness of the top layer is less than the transport mean free path   (  0.1  -  0.8l  *    )  . We utilize an analytic forward solver, based upon the N'th-order spherical harmonic expansion with Fourier decomposition   (  SHEFN  )   method in conjunction with a multistage inverse solver. We test our method with data obtained using spatial frequency-domain spectroscopy with 32 evenly spaced wavelengths within λ  =  450 to 1000 nm on six-layered tissue phantoms with distinct optical properties. We demonstrate that this approach can recover absorption and reduced scattering coefficient spectra for both layers with accuracy comparable with current Monte Carlo methods but with lower computational cost and potential flexibility to easily handle variations in parameters such as the scattering phase function or material refractive index. To our knowledge, this approach utilizes the most accurate deterministic forward solver used in such problems and can successfully recover properties from a two-layer media with superficial layer thicknesses.

The refractive index gradient of the eye lens is controlled by the concentration and distribution of its component crystallin proteins, which are highly enriched in polarizable amino acids. The current understanding of the refractive index increment ([Formula: see text]) of proteins is described using an additive model wherein the refractivity and specific volume of each amino acid type contributes according to abundance in the primary sequence. Here we present experimental measurements of [Formula: see text] for crystallins from the human lens and those of aquatic animals under uniform solvent conditions. In all cases, the measured values are much higher than those predicted from primary sequence alone, suggesting that structural factors also contribute to protein refractive index.

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]

Copyright of Equine Veterinary Journal is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Detections of internal substances and morphologies for label-free living cells are crucial for revealing malignant diseases. With the phase serving as a coupling of refractive index (RI) (marker for substances) and thickness (morphology), existing decoupling methods mainly rely on complex integrated systems or extensive optical field information. Developing simple and rapid decoupling methods remains a challenge. This study introduces a refractive index morphology imaging microscope (RIMIM) system utilizing polarization multiplexing for label-free single living cells. By simultaneous degree of circular polarization (DOCP) imaging and noninterferometric quantitative phase imaging (QPI), the intracellular refractive index distribution (IRID) and morphology can be decoupled. The optical thickness calculated from the phase is input into the circular depolarization decay model (CDDM) of degree of circular polarization to retrieve IRID. Subsequently, the thickness can be decoupled from phase result using retrieved IRID. Experiments conducted on mouse forestomach carcinoma (MFC) cells and human kidney-2 cells (HK-2) demonstrated the RIMIM system's ability to retrieve IRID and decouple fine morphology. Additionally, the RIMIM system effectively detected membrane damage and changes in erastin-induced ferroptotic HK-2 cells, with average and root-mean-square of surface folds 65.5% and 70.0% higher than those of normal HK-2 cells. Overall, the RIMIM system provides a simple and rapid method for decoupling RI and fine morphology, showing great potential for label-free live cells' cytopathology detection.

Four biobased phosphate-containing aryl monomers with methoxy, allyl, and vinyl groups as substituents have been successfully synthesized. Copolymerizing these monomers with thiophenol or mercaptans via the photoclick thiol-ene reaction gives the polymers with refractive indices ( n D ) of 1.63-1.70 and Abbe numbers ( v D ) of 12.8-38.5. An investigation of the relationship of the v D values with the substituents on the benzene rings of the monomers indicates that methoxy and vinyl groups can collectively increase the v D values. In comparison with allyl groups, vinyl groups endow the polymers with both higher n D and v D . Moreover, these polymers also display high transmittance, high thermostability, and low haze values in the visible-light region, suggesting that these biobased functional monomers are satisfactory precursors used in the fabrication of optical devices.

Objective. Achieving ultra-precise temporal resolution in ionizing radiation detection is essential, particularly in positron emission tomography, where precise timing enhances signal-to-noise ratios and may enable reconstruction-less imaging. A promising approach involves utilizing ultrafast modulation of the complex refractive index, where sending probe pulses to the detection crystals will result in changes in picoseconds (ps), and thus a sub-10 ps coincidence time resolution can be realized. Towards this goal, here, we aim to first measure the ps changes in probe pulses using an ionizing radiation source with high time resolution . Approach. We used relativistic, ultrafast electrons to induce complex refractive index and use probe pulses in the near-infrared (800 nm) and terahertz (THz, 300 µ m) regimes to test the hypothesized wavelength-squared increase in absorption coefficient in the Drude free-carrier absorption model. We measured BGO, ZnSe, BaF 2 , ZnS, PBG, and PWO with 1 mm thickness to control the deposited energy of the 3 MeV electrons, simulating ionization energy of the 511 keV photons. Main results. Both with the 800 nm and THz probe pulses, transmission decreased across most samples, indicating the free carrier absorption, with an induced signal change of 11% in BaF 2 , but without the predicted Drude modulation increase. To understand this discrepancy, we simulated ionization tracks and examined the geometry of the free carrier distribution, attributing the mismatch in THz modulations to the sub-wavelength diameter of trajectories, despite the lengths reaching 500 µ m to 1 mm. Additionally, thin samples truncated the final segments of the ionization tracks, and the measured initial segments have larger inter-inelastic collision distances due to lower stopping power (d E /d x ) for high-energy electrons, exacerbating diffraction-limited resolution. Significance. Our work offers insights into ultrafast radiation detection using complex refractive index modulation and highlights critical considerations in sample preparation, probe wavelength, and probe-charge carrier coupling scenarios., (© 2024 Institute of Physics and Engineering in Medicine. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

In this work, we report on the application of the polarization modulated spectroscopic ellipsometry-based surface plasmon resonance method for sensitive detection of microorganisms in Kretschmann configuration. So far, rotating analyzer and single wavelength polarization modulation methods have widely been investigated for phase sensitive surface plasmon resonance measurement. In this study, a much simpler optical setup relying on fast electro-optic phase modulator crystals is introduced for bacteria detection. A beta barium borate crystal connected to a function generator is adapted for generating phase shifts in the millisecond regime to extract the ellipsometric angles ( Ψ and Δ ) under the surface plasmon resonance condition. For detection, the gold surface was functionalized with anti-Escherichia coli antibodies, and E. coli K12 was attached to them. We show that polarization modulated spectroscopic ellipsometry achieves a refractive index resolution in the order of 10 - 5 RIU, and a limit of detection of 10 2 CFU/mL for E. coli K12 which is compatible with other surface plasmon resonance based phase sensitive methods with more complex detection concepts. As a follow-up step, an optical model can be developed to enhance this biosensor's performance, and applications for sorting and detecting other biological targets will be investigated., (© 2024. The Author(s).)

The research had in view to evaluate and compare two instrumental techniques used for the determination of milk lactose. Refractometric and polarimetric measurements were carried out on milk serum obtained after precipitation of casein by two different methods: by acidification of milk to its isoelectric point (E1), and by using copper sulphate and potassium ferrocyanide (E2). The average lactose content measured by refractometry was 5.469±0.256 g% for method E1 and 5.852±0.218 g% for method E2. The obtained average lactose values measured by polarimetry were higher both for E1 (5.613±0.253 g%) and E2 (5.910±0.224 g%) methods, due to the interference with other optically active components. The experimental data revealed a high correlation between the results obtained by refractometry and polarimetry (r=0.8712) when casein precipitation was performed by potentiometric titration until pH=4.6, at 25°C with 2N acetic acid (method E1).

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Water is the ubiquitous substance in nature (in all existing materials on the earth and every living creature) and is an essential substance for life. Water plays an essential role in the physical and chemical functions of living organisms. The water content is important for the processing and handling of the following product categories: food, pharmaceutical, cosmetic, personal care, household products, etc. Also, water has an important role in various industries such as in the various branches of the food industry, the pulp and paper industry, the pharmaceutical industry, etc. The water content of certain materials can be very difficult to determine due to the complexity of the water molecule and its strong intermolecular bonding capabilities. Most of the time, the measuring water content is better defined by measuring moisture content. [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]