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A novel fiber optic sensor for the simultaneous measurement of refractive index and temperature is reported. The sensor consists of a high-birefringence fiber loop mirror and a section of single mode-coreless-single mode fiber structure. The single modecoreless- single mode fiber structure served as a refractometer while the high-birefringence fiber loop mirror was used to measure temperature. The multimode interference valley of the single mode-coreless-single mode fiber structure was sensitive to the surrounding refractive index of liquids (96.42 nm/ refractive index unit) and had almost no response to temperature fluctuations. The high-birefringence fiber loop mirror was highly sensitive to temperature (1.98 nm/°C) but was insensitive to changes in refractive index. The theoretical and experimental results demonstrated simultaneous measurement of temperature and refractive index. The optimum resolution was 2.07 × 10-4 refractive index units and 0.01°C. [ABSTRACT FROM AUTHOR]

Calves are highly dependent of colostrum (and antibody) intake because they are born agammaglobulinemic. The transfer of passive immunity in calves can be assessed directly by dosing immunoglobulin G (IgG) or by refractometry or Brix refractometry. The latter are easier to perform routinely in the field. This paper presents a protocol for a systematic review meta-analysis to assess the diagnostic accuracy of refractometry or Brix refractometry versus dosage of IgG as a reference standard test. With this review protocol we aim to be able to report refractometer and Brix refractometer accuracy in terms of sensitivity and specificity as well as to quantify the impact of any study characteristic on test accuracy. [ABSTRACT FROM AUTHOR]

We have developed a new low-pressure sensor which is based on the measurement of (nitrogen) gas refractivity inside a Fabry-Perot cavity. We compare pressure determinations via this laser refractometer to that of well-established ultrasonic manometers throughout the range 100 Pa to 180 000 Pa. The refractometer demonstrates 10-6 ・ p reproducibility for p > 100 Pa, and this precision outperforms a manometer. We also claim the refractometer has an expanded uncertainty of U(pFP) = [(2.0 mPa)2 + (8.8 × 10-6 ・ p)2]1/2, as realized through the properties of nitrogen gas; we argue that a transfer of the pascal to p < 1 kPa using a laser refractometer is more accurate than the current primary realization. [ABSTRACT FROM AUTHOR]

In the scope of miniaturized optical sensors for liquid refractometry, this work details the design, numerical simulation, and experimental characterization of a Fabry-Pérot resonator consisting of two deeply-etched silicon cylindrical mirrors with a micro-tube in between holding the liquid analyte under study. The curved surfaces of the tube and the cylindrical mirrors provide three-dimensional light confinement and enable achieving stability for the cavity illuminated by a Gaussian beam input. The resonant optofluidic cavity attains a high-quality factor (Q)--over 2800--which is necessary for a sensitive refractometer, not only by providing a sharp interference spectrum peak that enables accurate tracing of the peak wavelengths shifts, but also by providing steep side peaks, which enables detection of refractive index changes by power level variations when operating at a fixed wavelength. The latter method can achieve refractometry without the need for spectroscopy tools, provided certain criteria explained in the details are met. By experimentally measuring mixtures of acetone-toluene with different ratios, refractive index variations of 0.0005 < Δn < 0.0022 could be detected, with sensitivity as high as 5500 μW/RIU. [ABSTRACT FROM AUTHOR]

Nondestructive sugar content analysis of fruits is important for effective quality monitoring during growing stages, postharvest storage, and distribution in markets. The requirement of nondestructive analysis can be satisfied by an optical spectroscopic technique with an appropriate data analysis approach. We applied near-infrared ( NIR) diffuse-reflectance spectroscopy in combination with multivariate calibration as the nondestructive method of sugar content analysis for Korean pears. The diffuse-reflectance spectra for 21 Korean pears with the sugar contents of 10.3−12.9 °Bx were obtained in the wavelength region between 900 and 1500 nm. The differential spectrum of the pear samples with the maximum and minimum sugar contents was found to show structures similar to those of the transmittance spectrum of an aqueous solution of glucose. This confirms that the NIR spectra of pears convey the quantitative chemical information of sugar molecules. A simple, effective spectral intensity normalization method was applied to improve the analysis precision. Based on the normalized NIR spectra, a multivariate calibration model was developed using partial least squares regression for predicting the sugar content of the Korean pear samples. The prediction accuracy was evaluated to be ~0.24 °Bx by the test set switch method. [ABSTRACT FROM AUTHOR]

An indium tin oxide (ITO) refractometer based on the generation of lossy mode resonances (LMRs) and surface plasmon resonances (SPRs) is presented. Both LMRs and SPRs are excited, in a single setup, under grazing angle incidence with Kretschmann configuration in an ITO thinfilm deposited on a glass slide. The sensing capabilities of the device are demonstrated using several solutions of glycerin and water with refractive indices ranging from 1.33 to 1.47. LMRs are excited in the visible range, from 617 nm to 682 nm under TE polarization and from 533 nm to 637 nm under TM polarization, with a maximum sensitivity of 700 nm/RIU and 1200 nm/RIU, respectively. For the SPRs, a sensing range between 1375 nm and 2494 nm with a maximum sensitivity of 8300 nm/RIU is measured under TM polarization. Experimental results are supported with numerical simulations based on a modification of the plane-wave method for a onedimensional multilayer waveguide. [ABSTRACT FROM AUTHOR]

Optical microcavities enable circulated light to intensively interact with a detecting liquid, thus promising high sensitivity in fluidic refractometers. Based on Mie scattering theory, we propose a tubular metamaterial device for liquid sensing, which utilizes anisotropic metamaterials with hyperbolic dispersion called indefinite media (IM). Besides traditional whispering gallery modes (WGMs), such tubular cavities can support surface plasmon polariton (SPP) WGMs, enabling high sensitivity liquid detection. Three configurations of such metamaterial tubes for sensing are discussed: tube-in-liquid, hollow-tube-in-liquid and liquid-in-tube; these are analyzed using numerical formulas and compared with dielectric and metal materials. Compared with traditional dielectric media (DM), the IM tubular cavity exhibits a higher sensitivity (S), which is close to that of a metal tubular cavity. However, compared with metal media, such an IM cavity can achieve higher quality (Q) factors similar to the DM tubular cavity. Therefore, the IM tubular cavity can offer the highest figures of merit (QS) for the sensing performance among the three types of materials. Our results suggest a novel tubular optofluidic device based on metamaterials, which could be useful for liquid refractometers. [ABSTRACT FROM AUTHOR]

Deriving the refraction index over temperature and concentration is essential in thermal diffusion measurements. In the present study, we attempt to provide precise experimental measurements of the optical contrast factors of two ternary systems formed by three hydrocarbon components – 1,2,3,4-tetrahydronaphtalene (THN), isobutylbenzene (IBB), andn-dodecane. For each system we consider three different contrast factors:, and. The mixtures were prepared and investigated using a wide range of temperatures and wavelengths. The refractive index was measured using both the Mach–Zehnder Interferometer (MZI) and the multi-wavelength Abbemat Refractometer. A new development of the MZI cell holder used in the literature to measure contrast factors was presented and tested on ternary mixtures. In addition, this study compared the values of the experimental measurements of the refractive indices with theoretically estimated values using the mixing rules. The experimental values were in substantial agreement with all of the predictive values with the exception of the Oster (O) and Newton (N) equations. [ABSTRACT FROM PUBLISHER]

This study reports on development of the interference lithography (IL) technique applying the resist based on chalcogenide glass films for fabrication of gold chips in the form of periodic surface nanostructures for surface plasmon resonance (SPR) refractometers. The IL technique was optimized for patterning the Au layers and formation of one-dimensional (grating) structures with the spatial frequency close to 3300 mm-1. The spatial frequency and depth of grating grooves were selected with account of the condition for Bragg reflection of plasmons at the operation wavelength of SPR refractometer and given environment (which is a condition for enhancing biosensor sensitivity as compared to that of a flat Au chip surface). It has experimentally been demonstrated that the use of diffraction patterns in SPR sensor increases its response by 17%. [ABSTRACT FROM AUTHOR]

This study proposes an optical sensor based on a refractometer integrating a bend waveguide and a trench structure. The optical sensor is a planar lightwave circuit device involving a bend waveguide with maximum optical loss. A trench structure was aligned with the partially exposed core layer's sidewall of the bend waveguide, providing a quantitative measurement condition. The insertion losses of the proposed 1 × 2 single- mode optical splitter-type sensor were 4.38 and 8.67 dB for the reference waveguide and sensing waveguide, respectively, at a wavelength of 1550 nm. The optical loss of the sensing waveguide depends on the change in the refractive index of the material in contact with the trench, but the reference waveguide had stable optical propagating characteristics regardless of the variations of the refractive index. [ABSTRACT FROM AUTHOR]

The serum of patients with multiple myeloma was examined by refractometric methods before and after the course of antitumor therapy. It was found that the amount of protein in the serum of patients with multiple myeloma, determined by the value of the serum refractive index, tended to decrease after the course of treatment. The value of the refractive index of blood serum can be used as an additional criterion for assessing the dynamics of changes in blood-serum properties during antitumor therapy. [ABSTRACT FROM AUTHOR]

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Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications. [ABSTRACT FROM AUTHOR]

A semiempirical method has been proposed for evaluating oxygen deficiency δ in LaSrMnO (LSMO) films on oxide substrates by comparing a measured refractive index with the refractive index calculated as a function of δ. [ABSTRACT FROM AUTHOR]

A heterogeneous sensor system to determine the ethanol concentration in ethanol–water solution is demonstrated. The system consists of an optical-fiber refractometric transducer based on a long-period grating and a pair of ultrasonic transducers in transmission–reception mode, connected to a stand-alone electronic board for data acquisition, storage, and signal preprocessing. To implement a coherent sensor fusion from both measurement techniques, two soft computing methods (artificial neural network model and neuro-fuzzy model) are studied. A comparative analysis of these models was carried out based on the measured data. The best performance was obtained with the neural-network-based model. This model showed that it was able to correlate the responses of the optical-fiber transducer and the ultrasound system with the ethanol–water concentration. The final performance of the heterogeneous system is better within the whole range of concentrations, even if compared with the best performance of the individual sensors for limited ranges. [ABSTRACT FROM PUBLISHER]

We present two approaches for measuring the refractive index of transparent solids in the visible spectral range based on diffraction gratings. Both require a small spot with a periodic pattern on the surface of the solid, collimated monochromatic light, and a rotation stage. We demonstrate the methods on a polydimethylsiloxane film (Sylgard® 184) and compare our data to those obtained with a standard Abbe refractometer at several wavelengths between 489 and 688 nm. The results of our approaches show good agreement with the refractometer data. Possible error sources are analyzed and discussed in detail; they include mainly the linewidth of the laser and/or the angular resolution of the rotation stage. With narrow-band light sources, an angular accuracy of ±0.025° results in an error of the refractive index of typically ±5 · 10-4. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to report normative values and ranges of interpupillary distance (IPD) in different age groups of a Turkish population. Methods: A total of 756 healthy subjects were included in this prospective study. After a complete ophthalmic evaluation, subjects were divided into four age groups to assess differences between age groups in relation to IPD. The age groups were 20-30, 31-50, 51-70, and 71-89 years. Far IPD measurements were performed using an autorefractometer (Topcon RM-8800). Results: The mean age was 48.42±20.55 years, ranging from 19 to 89 years. The mean IPD was calculated as 62.5±4.1 mm (range 49-76). The mean IPD value was observed to be significantly higher among males compared to females (P<0.001). The difference among groups in terms of mean IPD was statistically significant (P<0.001). IPD increased by 4.19 mm in males and 3.11 mm in females from the young adults (20-30 years) to older adults (51-70 years), and then a decrease (2.6 and 0.19 mm for males and females, respectively) occurred between 70 and 89 years of age. Conclusion: The current study offers the population-specific normative data on far IPD in different age groups. Our study showed that sex and age had a significant effect on IPD. Knowledge of normal values in this population subgroup may be useful in studying orbito-cranial growth patterns, syndrome diagnosis, surgical management of cranio-facial deformities and trauma, and manufactures of optical frames and lenses. [ABSTRACT FROM AUTHOR]

A novel reflective refractometer based on a fiber Bragg grating (FBG) inscribed in a thin-core-fiber (TCF) stub was demonstrated. The cladding modes are excited by the core diameter mismatch between the single-mode-fiber (SMF) and TCF. The core mode and specific cladding modes in the TCF are reflected by the FBG and partly recoupled into the back-propagating core mode in the SMF. Experimental results demonstrate that the power of the cladding mode reflection changes with the surrounding refractive index (SRI). The temperature-immune SRI measurement with linear sensitivity of 54.55 dB per refractive index unit has been achieved by the cost-effective power detection within the refractive index range from 1.33 to 1.42. To eliminate the measurement deviation caused by the fluctuation of light source, the simple self-referencing detecting has been carried out by measuring the ratio of the cladding mode reflection and the core mode reflection. [ABSTRACT FROM AUTHOR]

In this paper, the design and testing of a five-wavelength laser microrefractometer are presented. Five semiconductor lasers are used for the spectral region of 405-1320 nm. The presented device is based on the critical angle method. In this case, the critical angle of total internal reflection is determined with the help of a CCD camera detecting the disappearance of the diffraction pattern, created by a metal diffraction grating. The samples of a thin liquid layer (< 10 μm) are placed between a flint-glass prism and a chromium diffraction grating. The refractive indices of two matching liquid products of Cargille Laboratories are investigated for the approbation of the presented device. The measured values of the refractive indices are used for the dispersion curves construction. The obtained values of the refractive indices are compared with the catalog data given by the manufacturer. [ABSTRACT FROM AUTHOR]

In this work, optical fiber refractometers based on the successive incorporation of gold nanoparticles have been fabricated by means of the Layer-by-Layer Embedding (LbL-E) deposition technique. This enables the apparition of two different optical phenomena, Localized Surface Plasmon Resonance (LSPR) and Lossy Mode Resonance (LMR). The absorption peaks related to both phenomena were captured during the fabrication process, showing a different evolution as a function of the resultant thickness coating. Initially, LSPR band is observed for thinner coatings, whereas multi-LMR bands are observed as the thickness coating is increased. In addition, the response of both phenomena to variations of the surrounding medium refractive index (SMRI) was monitored, studying their different sensitivities. LSPR band only shows intensity variation with negligible wavelength displacement whereas LMR bands present a strong wavelength response. The combination of both resonances opens the door in the design of self-referenced optical devices for sensing applications. [ABSTRACT FROM AUTHOR]

Background and purposeRefractometers have gained a foothold in childhood screening for ophthalmic disorders. Given the results of an ophthalmic follow-up of an extremely preterm Danish cohort, the results of the Retinomax autorefractor were further evaluated.Materials and methodsA nationwide cohort of infants born before gestational age 28 weeks (n=178) and 56 term controls were examined at the age of 4 years. Refraction was given as the cycloplegic Retinomax value. For this study, we analysed the equipment's confidence value on the printout and equipment-induced myopization (as the difference between refraction measured before and after topical cyclopentholate 1%), both items hypothetical with a view to having identified factual ophthalmic deviations.ResultsThirty-two of 42 eyes with visual acuity ≤0.4 had high Retinomax confidence values (8-9); the Retinomax values were also high in 10 of 12 children with strabismus and lack of stereopsis. Low values (1-6) were recorded in 11 single eyes, 5 of which were normal (false positives). Three children already known to have low vision were unable to cooperate. The overall mean value for equipment-induced myopization was 1.9 D (range, 0-6.87 D). Myopization showed no correlation with visual acuity and corneal curvature, and a weak positive correlation with refractive value disappeared when the myopic outliers were excluded.ConclusionsThe hand-held Retinomax seemed to be reliable for assessing refraction in 4-year-old children, provided a cycloplegic agent is applied; if used alone, the Retinomax would have missed several cases of ophthalmic deviation during screening. Equipment-induced myopization was not indicative. [ABSTRACT FROM AUTHOR]

In the present study the ordinary refractive indices of Nematic liquid crystal (LC), Cholesteric liquid crystal and their mixtures were measured by multiple wavelength refractometer in the visible range with temperature range from 20°C to 80°C. As the wavelength increases, the refractive indices may decrease. As the temperature increases, the refractive index may decrease. The ordinary refractive index decreases or increases depending on the crossover temperature of the Liquid Crystal employed. The wavelength- and the temperature-dependent refractive indices are fundamentally interesting and practically important for optimizing the display performances and other photonic devices employing LCs. We also tried to investigate factors affecting the temperature gradient of ordinary refractive index (dno/dT).Liquid crystal should exhibit a large temperature gradient refractive index to reduce the required laser intensity for triggering the nonlinear optical effects. The two crucial parameters for achieving large dno/dT are high birefringence and low clearing point. However, these two requirements are often conflicting each other. The temperature at which dno/dT = 0 is called the cross-over temperature To. If Tc, the clearing temperature of liquid crystal material is much higher than the room temperature then the cross-over temperature would be relatively high and dno/ dT < 0 at room temperature. From all the investigations it is observed that the values of refractive index change with temperature, wavelengths as well as with the mixture. Some of the liquid crystal mixtures show excellent index matching property. [ABSTRACT FROM AUTHOR]

This paper presents the design and simulation results of a high-precision low-cost refractometer that demonstrates the main advantage of a wide measurement range (1 ≤ n ≤ 2). The proposed design is based on the diffractive properties of sub-micron gratings and Snell's Law. The precision and uncertainty factors of the proposed system were tested and analyzed, revealing that the proposed refractometer demonstrates a wide measurement range with sensitivity of 10-4. [ABSTRACT FROM AUTHOR]

A method for measuring refractive index n of nanosize particles in the visible and near-IR spectral ranges is proposed. The method is based on comparing refractive index n of a colloid solution of nanoparticles in several solvents with refractive indices n of corresponding pure solvents and has an accuracy of ±2 × 10. Upconversion nanosize phosphors (UCNPs) are synthesized in the form of a β-NaYF crystalline matrix doped with Yb, Er, and Tm rare earth ions. UCNPs have a doped core with a diameter of 40 ± 5 nm and undoped shell with a thickness of 3-5 nm. Synthesized nanocrystals possess intense photoluminescence in the blue, green, and red spectral ranges upon excitation by IR radiation with a wavelength of 977 nm. Using a spectroscopic refractometer, the dispersion of the refractive index of β-NaYF/Yb/Er/Tm nanocrystals was measured for the first time in the spectral range of 450-1000 nm with an accuracy of ±2 × 10. [ABSTRACT FROM AUTHOR]

Many optical systems based on surface plasmon resonance (SPR) have been developed for working as refractometers, chemical sensors or even for measuring the thickness of metal and dielectric thin films. Sensors based on SPR present very high sensitivity to refractive index (RI) variations when compared to the traditional RI sensors. However, these kinds of systems are usually large, expensive and therefore cannot be used for remote sensing. Optical fibre sensors based on SPR are usually implemented using multimode optical fibres cope with the requirements for remote sensing. In this section a new type of SPR sensor based in a single mode fibre (SMF) is proposed. A section of the SMF was chemically etched by emersion in a 48 % hydrofluoric acid solution, resulting in a tapering effect, with the cladding removing while the core is kept intact. Simulation results are in good agreement with the experimental spectral resonance dip attained around 1550 nm. Sensitivities of 3800 and 5100 nm/RIU were achieved for the reflection and for the transmission modes, respectively, for RI in the 1.33 to 1.37 range. [ABSTRACT FROM AUTHOR]

The isotropic - blue phases - cholesteric phase transitions are studied in a thermotropic (COC) by image processing and refractive index measurements. Textures of blue phases are optically characterized as well as their transition points. The experimental investigation employed here is sensitive to detect changes in the structural configuration of blue phases as a consequence of our refractive index data. In this context the experimental results are presented and discussed. [ABSTRACT FROM AUTHOR]

In this work, we studied the chain dimensions, shape, and thermodynamic characteristics of poly(ε-caprolactone) diols (HO-PCL-OH) in solution. PCL diol samples of different molecular weights and architectures were synthesized using immobilized Yarrowia lipolytica lipase as catalyst. Gel permeation chromatography (GPC) with online right-angle laser-light scattering (RALLS), differential viscometer (DV), and interferometric refractometer IRS detectors offered a proper way to obtain information on thermodynamic characteristics and chain flexibility. The weight-average molecular weights of the PCL diol samples ( M) ranged from 2,750 to 13,120 uma. The z-average radius of hydrodynamic volume ( ) vs. z-average molecular weight curve ( M) could be satisfactorily fitted to a power-law equation. Mark-Houwink-Sakurada parameters ( K = 2.74 × 10 dL/g and a = 0.64) were derived from the plots of [η] against M. The overall results clearly suggest that a flexible geometry is present in tetrahydrofuran (THF) solution of PCL at 33 °C. Unlike other PCL systems, PCL diols are more hydrophilic and expected to form associated species. They behave differently from common hydrophobic polymers and do not strictly conform to thermodynamic relationships generally used in Polymer Science. A more compact geometry is present for M lower than 4,000 Da. For higher molecular weights, the chain expands and become more elongated. Plots of ln [η] against ln M (MHS equation) and of log R against log M suggest that PCL diols behave as flexible chains in a good solvent. [ABSTRACT FROM AUTHOR]

Background Failure of transfer of passive immunity ( FTPI) is the underlying predisposing risk factor for most early losses in dairy calves. Refractometers, either optical or digital, can be used to assess FTPI as a part of calf health monitoring program on dairy operations. Objectives To evaluate the performance of and differences between digital Brix and optical refractometers for assessing FTPI in dairy calves. Animals Two hundred Holstein calves from 1 to 11 days of age. Methods A cross-sectional study was designed to measure serum Ig G concentration by radial immunodiffusion ( RID) assay, digital Brix and optical refractometers. The correlation coefficients ( r) between the 2 refractometers were plotted against each other and against the measured Ig G concentration from RID. The Se, Sp, and accuracy of digital Brix and optical refractometers for assessing FTPI using previously recommended cut-offs were calculated. A receiver operating characteristic curve was created and used to identify the optimal cut-off for this dataset. Results The RID Ig G concentration was positively correlated with digital Brix ( r = 0.79) and optical ( r = 0.74) refractometers. The best combination of Se (85.5%), Sp (82.8%), and accuracy (83.5%) of digital Brix refractometer was at 8.3% Brix. For optical refractometer, the best combination of Se (80%), Sp (80.7%), and accuracy (80.5%) was at 5.5 g/dL. Conclusions and Clinical Importance Both refractometers exhibited utility in assessing FTPI in dairy calves. [ABSTRACT FROM AUTHOR]

The evaluation of weight average molecular weight (Mw) and molecular weight distribution represents one of the most controversial aspects concerning the characterization of low molecular weight heparins (LMWHs). As the most commonly used method for the measurement of such parameters is high performance size exclusion chromatography (HP-SEC), the soundness of results mainly depends on the appropriate calibration of the chromatographic columns used. With the aim of meeting the requirement of proper Mw standards for LMWHs, in the present work the determination of molecular weight parameters (Mw and Mn) by HP-SEC combined with a triple detector array (TDA) was performed. The HP-SEC/TDA technique permits the evaluation of polymeric samples by exploiting the combined and simultaneous action of three on-line detectors: light scattering detectors (LALLS/RALLS); refractometer and viscometer. Three commercial LMWH samples, enoxaparin, tinzaparin and dalteparin, a γ-ray depolymerized heparin (γ-Hep) and its chromatographic fractions, and a synthetic pentasaccharide were analysed by HP-SEC/TDA. The same samples were analysed also with a conventional HP-SEC method employing refractive index (RI) and UV detectors and two different chromatographic column set, silica gel and polymeric gel columns. In both chromatographic systems, two different calibration curves were built up by using (i) γ-Hep chromatographic fractions and the corresponding Mw parameters obtained via HP-SEC/TDA; (ii) the whole γ-Hep preparation with broad Mw dispersion and the corresponding cumulative distribution function calculated via HP-SEC/TDA. In addition, also a chromatographic column calibration according to European Pharmacopoeia indication was built up. By comparing all the obtained results, some important differences among Mw and size distribution values of the three LMWHs were found with the five different calibration methods and with HP-SEC/TDA method. In particular, the detection of the lower molecular weight components turned out to be the most critical aspect. Whereas HP-SEC/TDA may underestimate species under 2 KDa when present in low concentration, other methods appeared to emphasize their content. [ABSTRACT FROM AUTHOR]

Tapered fibers are used in multitude of applications due to its great versatility and functionality. In particular, this type of fibers is especially useful for sensing applications. For this purpose, tapered fibers must be adequately manipulated to avoid disturbances in the sensor's response. In this paper, a guideline for the correct handling of biconical tapered fibers during refractive index and strain measurements is presented and analyzed considering several manipulation scenarios and its corresponding influence in the performance of the system. [ABSTRACT FROM PUBLISHER]

CO2 capture is still a major challenge for the environment and decarbonization of gas streams. It has been industrially feasible for several decades using chemical absorption by alkanolamine solvents. The purpose of this work is to characterize the mass transfer in a spray contactor during CO2 absorption using monoethanolamine as a solvent. A new, effective way to investigate mass transfer is to measure the refractive index during the reactive absorption. Indeed, the concentration and temperature evolution inside the droplet during absorption induces a modification of the refractive index. By using rainbow refractometry technique (GRT), the liquid side mass transfer coefficient was measured in a controlled gas atmosphere during a transfer process in aqueous 30 % (w/w) monoethanolamine and compared to the literature. [ABSTRACT FROM AUTHOR]

Objectives To investigate the accuracy of both the optical and digital Brix refractometers compared with radial immunodiffusion ( RID) for determining the immunoglobulin G ( IgG) concentrations in dairy calf serum. Design The experiment design was a cross-sectional survey of four dairy farms. Serum was sampled from 12 calves from each farm at approximately 48 hours of age. Methods Serum IgG concentrations of 48 calves were measured using RID and both types of Brix refractometer. Results IgG concentrations measured by Brix refractometer scores correlated with RID results: 0.74 and 0.71 for the digital and optical devices, respectively. The minimum Brix score that identified calf serum with success of passive immunity (>1000 mg/dL RID IgG) with 100% accuracy was 10% for both devices. The optical and digital devices performed similarly at identifying IgG concentrations in calf serum, with a concordance of 87%. Conclusion Brix refractometer score ≥10% can be used to classify calves with successful transfer of passive immunity and the devices are sufficiently accurate for use as a simple, inexpensive on-farm tool for the monitoring of neonatal dairy calf immunity levels. [ABSTRACT FROM AUTHOR]

In observing the stereoscopic display at the viewing distance of 1 m, the amount of the perceived depth was determined by the positions of the crossing point that the viewing direction of two eyes intersect. The positions of the crossing points of stereoscopic stimuli were controlled, and the accommodation was measured by the autorefractometer for the seven participants. Accommodation was also measured when viewing the real film chart which was placed at the same position as these crossing points. The accommodation change when viewing the stereoscopic display was measured to be noticeable only when the crossing point was quite near the participant, but this change was still much smaller compared with the accommodation change when viewing the real film chart. This change in accommodation implies the possible occurrence of fatigue related to the accommodation-convergence conflict, while the constant accommodation within the range of DOF implies no conflict between the accommodation and convergence. This measurement scheme may be used to define the range of DOF where the accommodation remains little changed, and thus define the depth of the 3D object at which no accommodation-convergence conflict occurs, for a given stereoscopic display. [ABSTRACT FROM AUTHOR]

In this letter, we present a novel fiber-optic Mach-Zehnder interferometer based on leaky-mode generation from fiber bending and experimentally demonstrate it that is used as a fiber-optic refractometer. The interferometer is simply constructed using a standard single-mode fiber with two fiber bending regions connected by a section of straight fiber. The phase difference is from the optical path difference between the core mode and leaky modes from the designed bending fiber structure. Refractive index (RI) sensors with different parameters have been fabricated and tested in NaCl solutions with different RIs in the range of 1.3288-1.3696, and a maximum RI sensitivity of -204-nm/RIU (refractive index unit) is achieved on a sensor with a 4-cm straight fiber length and 5-mm bending radius. Experimental results have confirmed that there are two dominant cladding modes interfering with the core mode. The RI sensitivities of the sensors with a uniform bending radius are independent of the straight fiber length; as a result, precise control of the fiber length is not required, which makes the sensor production cost-effective. [ABSTRACT FROM PUBLISHER]

In the last 4 years, experimental evidences about the potential use of optical sensors based on Lossy Mode Resonances (LMR) have been presented in the literature. These LMR sensors have some similarities with Surface Plasmon Resonance (SPR) sensors, the gold standard in label-free, real-time biomolecular interaction analysis. In these new LMR sensors, if the non-metallic nano- cladding of an optical waveguide fulfills the conditions explained in this work, coupling of light to the cladding modes happens at certain resonance wavelengths, which enables the use of LMR devices as refractometers and opens the door to diverse applications such as in biology and proteomics research. These highly sensitive refractometers have already shown sensitivities higher than 20,000 nm/RIU or 5x10-7 RIU and, given the youth of this field, it is expected to achieve even better values. [ABSTRACT FROM AUTHOR]

This paper presents a biophysical method to characterize single bacterium in water by using an on-chip optofluidic immersion refractometer. Water safety is a major factor in the well-being of people, but the presence of bacteria such as Escherichia coli ( E. coli ), bacillus subtilis , Shigella flexneri and vibrio cholera in drinking water can lead to infectious diseases such as typhoid fever. Hence, it is crucial to detect and identify bacteria to prevent bacterial outbreaks. In this paper, an optofluidic immersion refractometer is developed to measure three biophysical parameters, i.e. size, shape and refractive index. The refractive index of a single bacterium is measured in high sensitivity of 0.005 RIU. This system is an innovative method to allow on-site real-time detection of single bacterium in water. It significantly reduces the amount of detection time and do not require trained personnel or additional chemical and biological reagents. [ABSTRACT FROM AUTHOR]

Deep ocean injection of carbon dioxide into subsea geologic formations carries a risk of carbon dioxide leakage as well as leakage of methane from petroleum bearing formations that injection wells may penetrate. Therefore, leakage monitoring technology for this application must detect carbon dioxide and distinguish it from methane. Here we demonstrate an all-optical approach to detect and differentiate between liquid carbon dioxide and supercritical methane bubbles in synthetic seawater at 9.65 MPa. This method employs fiber tip refractometry, a fiber optic measurement technique that is sensitive to the refractive index of the surrounding medium. Carbon dioxide and methane bubbles are clearly detected as they pass the sensor tip and these species are clearly distinguished from each other. Interferometric signals are also observed in association with the transition of bubbles onto and off of the sensor tip. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1038/s41598-022-15736-z. Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-15736-z, published online 09 July 2022 The original version of this Article contained an error in authors Affiliation, which was incorrectly given as 'Nano Biotechnology Research Centre, Indian Farmers Fertilizer Cooperative Limited, Gandhinagar, 382423, India'. [Extracted from the article]