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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]

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.

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.

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]

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]

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.

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.

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]

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.

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.

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]

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 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).

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.

BackgroundTransfer of passive immunity in calves can be assessed by direct measurement of immunoglobulin G (IgG) by methods such as radial immunodiffusion (RID) or turbidimetric immunoassay (TIA). IgG can also be measured indirectly by methods such as serum refractometry (REF) or Brix refractometry (BRIX).ObjectivesTo determine the accuracy of REF and BRIX for assessment of inadequate transfer of passive immunity (ITPI) in calves.DesignSystematic review and meta-analysis of diagnostic accuracy studies.MethodsDatabases (PubMed and CAB Abstract, Searchable Proceedings of Animal Science) and Google Scholar were searched for relevant studies. Studies were eligible if the accuracy (sensitivity and specificity) of REF or BRIX was determined using direct measurement of IgG by RID or turbidimetry as the reference standard. The study population included calves

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]

Copyright of Nouveau Praticien Vétérinaire Élevages et Santé is the property of EDP Sciences 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.)

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]

Background: Acute posterior multifocal placoid pigment epitheliopathy (APMPPE) is a rare inflammatory disease, and the differential diagnostic assessment is essential for its adequate treatment. Purpose: To perform clinical analysis and differential diagnosis for a case of APMPPE. Material and Methods: We present a case of a 26-year-old woman with APMPPE. The patient underwent an eye examination which included visual acuity assessment, refractometry, tonometry, perimetry, biomicroscopy, direct and indirect ophthalmoscopy, optical coherence tomography (OCT), fundus photography, and fluorescein angiography (FA). Endonasal electrophoresis was conducted in a routine manner using azithromycin, a macrolide antibiotic. Results: OCT found numerous flat yellowish-white and grey-pink lesions in the posterior pole of the fundus at the level of the retinal pigment epithelium and choriocapillary layers. FA showed irregularly shaped non-fluorescent lesions, which began to exhibit faint fluorescence a few minutes after the dye injection. The differential diagnosis should include serpiginous choroiditis, Vogt-Koyanagi-Harada syndrome, geographical choroiditis, acute retinal pigment epitheliitis (Krill disease), and choroidal neoplasm. Conclusion: Acute posterior multifocal placoid pigment epitheliopathy is an acuteonset disease. If the disease is suspected, a thorough history is essential, and the differential diagnosis should be performed for early treatment and referral to an appropriate specialist. Patients with this disease should be followed since recurrences can occur. [ABSTRACT FROM AUTHOR]

In recent years, following the outbreak of the COVID-19 pandemic, there has been a significant increase in cases of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) and related deaths worldwide. Despite the pandemic nearing its end due to the introduction of mass-produced vaccines against SARS-CoV-2, early detection and diagnosis of the virus remain crucial in preventing disease progression. This article explores the rapid identification of SARS-CoV-2 by implementing a multimode plasmonic refractive index (MMRI) optical sensor, developed based on the split ring resonator (SRR) design. The Finite Difference Time Domain (FDTD) numerical solution method simulates the sensor. The studied sensor demonstrates three resonance modes within the reflection spectrum ranging from 800 nm to 1400 nm. Its material composition and dimensional parameters are optimized to enhance the sensor's performance. The research indicates that all three resonance modes exhibit strong performance with high sensitivity and figures of merit. Notably, the first mode achieves an exceptional sensitivity of 557 nm/RIU, while the third mode exhibits a commendable sensitivity of 453 nm/RIU and a Figure of Merit (FOM) of 45 RIU -1 . These findings suggest that the developed MMRI optical sensor holds significant potential for the early and accurate detection of SARS-CoV-2, contributing to improved disease management and control efforts., (© 2024. The Author(s).)

This work discusses label-free biosensing application of a double-layer optical fiber interferometer where the second layer tailors the reflection conditions at the external plain and supports changes in reflected optical spectrum when a bio-layer binds to it. The double-layer nanostructure consists of precisely tailored thin films, i.e., titanium (TiO 2 ) and hafnium oxides (HfO 2 ) deposited on single-mode fiber end-face by magnetron sputtering. It has been shown numerically and experimentally that the approach besides well spectrally defined interference pattern distinguishes refractive index (RI) changes taking place in a volume and on the sensor surface. These are of interest when label-free biosensing applications are considered. The case of myeloperoxidase (MPO) detection-a protein, which concentration rises during inflammation-is reported as an example of application. The response of the sensor to MPO in a concentration range of 1 × 10 -11 -5 × 10 -6  g/mL was tested. An increase in the MPO concentration was followed by a redshift of the interference pattern and a decrease in reflected power. The negative control performed using ferritin proved specificity of the sensor. The results reported in this work indicate capability of the approach for diagnostic label-free biosensing, possibly also at in vivo conditions., (© 2024. The Author(s).)

The current limitations of single-molecule localization microscopy (SMLM) in deep tissue imaging, primarily due to depth-dependent aberrations caused by refractive index (RI) mismatch, present a significant challenge in achieving high-resolution images at greater depths. To extend the imaging depth, we optimized the imaging buffer of SMLM with the RI matched to that of the objective immersion medium and systematically evaluated five different RI-matched buffers, focusing on their impact on the blinking behavior of red-absorbing dyes and the quality of reconstructed super-resolution images. Particularly, we found that clear unobstructed brain imaging cocktails-based imaging buffer could match the RI of oil and was able to clear the tissue samples. With the help of the RI-matched imaging buffers, we showed high-quality dual-color 3D SMLM images with imaging depths ranging from a few micrometers to tens of micrometers in both cultured cells and sectioned tissue samples. This advancement offers a practical and accessible method for high-resolution imaging at greater depths without the need for specialized optical equipment or expertise.

Objectives: To evaluate the effect of different ratios of Bis-EMA/Bis-GMA resin mixtures on the inherent viscosity and curing-related properties: including degree of cure (DC%), shrinkage strain, Knoop micro-hardness (KH) and flexural strength of resin-impregnated fiber-bundles., Methods: Bis-EMA/Bis-GMA monomers were mixed (by weight) in the following ratios: M1 = 30 %/70 %, M2 = 50 %/50 %, M3 = 70 %/30 %, and M4 = 100 %/0 %. Standard measurements were made of refractive index, viscosity, degree of conversion, shrinkage strain and Knoop hardness (KHN). For 60 % glass fiber-bundles impregnated with 40 % resin, three-point bending test for flexural strength and shrinkage strain were measured. Data were analyzed by One-way ANOVA and Bonferroni post-hoc tests (α = 0.05)., Results: For resin mixtures, increasing Bis-EMA proportion decreased refractive index (p < 0.05), and viscosity (p < 0.05), and increased monomer conversion (DC%), shrinkage strain and KHN (p < 0.05). DC% increased after 1 h for all resin mixtures. The shrinkage strain and flexural strength of resin-impregnated fiber-bundles reduced with increased Bis-EMA., Significance: Monomeric mixtures with highest amounts of Bis-EMA showed enhancement in several clinically-relevant properties and polymerization of respective resin-impregnated glass fibers. This makes them potential candidates for impregnating glass fibers in fiber-reinforced restorations., Competing Interests: Declaration of competing interest This is to confirm there are no interests to declare regarding the above titled manuscript., (Copyright © 2024 Elsevier Inc. All rights reserved.)