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Nanomaterials are inherently polydisperse. Traditional techniques, such as the widely used batch-mode dynamic light-scattering (DLS) analysis, are not ideal nor thoroughly descriptive enough to define the full complexity of these materials. Asymmetric-flow field-flow fractionation (AF4) with various in-line detectors, such as ultraviolet-visible (UV-vis), multi-angle light scattering (MALS), refractive index (RI), and DLS, is an alternative technique that can provide flow-mode analysis of not only size distribution but also shape, drug release/stability, and protein binding., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10 -14  cm 2 /W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We demonstrated temperature-insensitive, label-free detection of SARS-CoV-2 spike protein (SSP) by harnessing the complementary refractive index and temperature dependence of multi-mode interference (MMI) created by a no-core fiber (NCF) and phase-matched resonance generated by a long-period fiber grating (LPFG). To combine MMI and grating resonance, primarily sensitive to the surrounding medium refractive index (SMRI) and ambient temperature, respectively, a fiber-optic transducer was fabricated by splicing an NCF segment with an LPFG inscribed on double-clad fiber. The transducer was functionalized with human ACE2 receptors to selectively capture SSP. The functionalized sensor head exhibited high SSP selectivity, with overall average wavelength displacements of ∼253.33 and ∼160.00 pm in PBS and saliva, respectively, for SSP with concentrations ranging from 1 to 10 4  ng/mL. These spectral shifts are associated with localized SMRI modulations on the sensor surface induced by specific binding between SSP and ACE2. We also examined the cross-reactivity of the sensor head for MERS-CoV spike protein to confirm its SSP specificity. Moreover, we proved the capability of temperature-independent SSP detection and ambient temperature measurement by scrutinizing the temperature effect on the sensor performance. Our functionalized fiber transducer showed great promise as a temperature-insensitive and portable platform for rapid SSP detection., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Yong Wook Lee reports financial support was provided by Korea Institute for Advancement of Technology. Yong Wook Lee reports financial support was provided by National Research Foundation of Korea., (Copyright © 2023. Published by Elsevier B.V.)

Refractive index sensing based on surface plasmon resonance (SPR) is a highly efficient label-free technique for biomolecular detection. The performance of this method is defined by the dielectric properties of a sensing layer and its structure. Nanohole arrays in thin metal films provide good refractive index sensitivity but often suffer from a large resonance linewidth, which limits their broad practical application in biosensorics. Coupling the broad plasmon modes to sharp resonances can reduce the peak widths, but at the same time it can also degrade the sensitivity. Here, we use Finite-Difference Time Domain simulations to study the factors affecting the sensing performance of gold-silica-gold optical cavities with nanohole arrays in the dielectric and top metal layers. We demonstrate that by tuning resonator size and inter-hole spacing, the performance of the biosensor can be optimized and the figure of merit of the order of 5-7 is reached.

A microfiber interferometer coated with sensitive films formed by amide bond between 3-Carboxy-4-fluorophenylboronic acid (FPBA) and polydopamine (PDA) for the detection of trace glucose concentration is designed and demonstrated. Due to a huge evanescent field, this microfiber interferometer has a very sensitive response to the refractive index (RI) of the surrounding environment, which has excellent sensing performance including RI sensitivity response of 1825.83 nm/RIU and low temperature response of -0.04 nm/°C. Due to the good film-forming performance of PDA, whose the amino group coupled with the carboxyl molecule on FPBA to form an amide bond, PDA/FPBA can be attached to the microfiber interferometer for detecting different concentrations of glucose. The concentration range of glucose detection is 0.1-20 mM with a sensitivity of 1.71 nm/mM and a limit of detection of 12.6 ppm. Finally, the sensor is tested in actual samples of human urine to detect different concentrations of glucose and proved to be responsive and reproducible in urine. We can estimate the concentration of glucose in urine by wavelength shift. The sensor has the advantages of simple manufacture, low cost, high sensitivity, and specific recognition glucose in urine. In addition, the success of this sensor shows that the combination of ultrafine fiber and organic chemical materials has broad prospects in the field of optical detection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Tamm Plasmon Polariton (TPP) is a nanophotonic phenomenon that has attracted much attention due to its spatial strong field confinement, ease of mode excitation, and polarization independence. TPP has applications in sensing, storage, lasing, perfect absorber, solar cell, nonlinear optics, and many others. In this work, we demonstrate a biosensing platform based on TPP resonant mode. Both theoretical analyses based on the transfer matrix method and experimental validation through nonspecific detection of liquids of different refractive indices and specific detection of SARS-CoV-2 nucleocapsid protein (N-protein) are presented. Results show that the TPP biosensor has high sensitivity and good specificity. For N-protein detection, the sensitivity can be up to 1.5 nm/(µg/mL), and the limit of detection can reach down to 7 ng/mL with a spectrometer of 0.01 nm resolution in wavelength shift. Both nonspecific detection of R.I. liquids and specific detection of N-protein have been simulated and compared with experimental results to demonstrate consistency. This work paves the way for design, optimization, fabrication, characterization, and performance analysis of TPP based biosensors.

Flow imaging microscopy (FIM) is widely used to characterize biopharmaceutical subvisible particles (SVPs). The segmentation threshold, which defines the boundary between the particle and the background based on pixel intensity, should be properly set for accurate SVP quantification. However, segmentation thresholds are often subjectively and empirically set, potentially leading to variations in measurements across instruments and operators. In the present study, we developed an objective method to optimize the FIM segmentation threshold using poly(methyl methacrylate) (PMMA) beads with a refractive index similar to that of biomolecules. Among several candidate particles that were evaluated, 2.5-µm PMMA beads were the most reliable in size and number, suggesting that the PMMA bead size analyzed by FIM could objectively be used to determine the segmentation threshold for SVP measurements. The PMMA bead concentrations measured by FIM were highly consistent with the indicative concentrations, whereas the PMMA bead size analyzed by FIM decreased with increasing segmentation threshold. The optimal segmentation threshold where the analyzed size was closest to the indicative size differed between an instrument with a black-and-white camera and that with a color camera. Inter-instrument differences in SVP concentrations in acid-stressed recombinant adeno-associated virus (AAV) and protein aggregates were successfully minimized by setting an optimized segmentation threshold specific to the instrument. These results reveal that PMMA beads can aid in determining a more appropriate segmentation threshold to evaluate biopharmaceutical SVPs using FIM., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Tapered profiles are introduced in Bessel and Blackman apodized fiber Bragg grating, and their sensing performance is theoretically estimated. Reflectivity equation of proposed apodized tapered profiles is obtained using transfer matrix method and coupled mode theory. Since the effective refractive index (RI) of proposed waveguides varies with core radius therefore amplitude distribution and penetration depth of light in surroundings are modified. It is found that the exponential tapered profile with Bessel apodization shows a higher sensitivity of 682.5 nm/RIU, detection accuracy of 3858.45, and quality parameter 1718.02/RIU with minimum full width at half maxima (FWHM) 0.3972 nm of the reflection spectra. The spectral response of the tapered fiber Bragg grating is also analyzed through a group delay study. Again, exponential profile was found to be particularly effective, producing less group delay ripples 2.98 ps and is maximum slope of 42.43°. Hence, exponential tapered profile is demonstrated for detection of cancer cells lies between the refractive index of 1.3333-1.4412., (© 2023 Wiley-VCH GmbH.)

The Optical Kerr Effect is investigated for the first time in biological tissues. This nonlinear effect was explored in both human brain and avian breast tissues using a time-resolved femtosecond pump-probe Optical Kerr Gate that looks for phase changes that arise in the probe from the pump induced Kerr refractive index change. The tissue samples produced a unique ultrafast (700-800 fs) doubled peaked temporal signal, which is indicative of interplay between the different ultrafast mechanisms (electronic plasma and molecular) that make up the Kerr index. The unique profile was replicated in theoretical simulations. The properties of the temporal profile varied between samples suggesting that it could be used as a new diagnostic. Understanding this behavior can help improve the scientific understanding of nonlinear spectral diagnostic techniques and potentially create a new Kerr-based optical biopsy method., (© 2023 Wiley-VCH GmbH.)

High refractive index polymers (HRIPs) are widely used in lenses, waveguide, antireflective layer and encapsulators, especially the advanced fields of augmented/virtual reality (AR / VR) holographic technology and photoresist for chip manufacturing. In order to meet the needs of different applications, the development of HRIPs focuses not only on the increase in refractive index but also on the balance of other properties. Sulfur-containing high refractive index polymers have received extensive attention from researchers due to their excellent properties. In recent years, not only ultrahigh refractive index sulfur-containing polymers have been continuously developed, but also low dispersion, low birefringence, high transparency, good mechanical properties, and machinability have been studied. The design of HRIPs is generally based on formulas and existing experience. In fact, molecular structure and properties are closely related. Mastering the structure-property relationship helps researchers to develop high refractive index polymer materials with balanced properties. This review briefly introduces the preparation methods of sulfur-containing high refractive index polymers, and summarizes the structure-property relationship between the sulfur-containing molecular structure and optical properties, mechanical properties, thermal properties, etc. Finally, the important role of synergistic effect in the synthesis of HRIPs and the prospect of future research on HRIPs are proposed., (© 2023 Wiley-VCH GmbH.)

Significance: This study provides a new method to measure the refractive index of crystalline lens in the human eye in vivo ., Purpose: Accessing the refractive index of crystalline lenses in the human eye in vivo has long been a challenge. This study aimed to measure the refractive index of a lens in vivo using an anterior segment optical coherence tomography (AS-OCT) system combined with a Scheimpflug imaging system., Method: A ray-traceable Scheimpflug imaging was developed and integrated into an AS-OCT system. A theoretical study revealed that the combination of these two systems provides a unique solution for simultaneously measuring the refractive index and the thickness of the lens. The average lens refractive index along the ray pathway ( Nav ) and lens shape were measured for seven subjects., Results: The lens Nav along the central ray varies from 1.383 to 1.419 between subjects. The lens refractive index function across the lens diameter varies from subject to subject. The lens Nav increases for accommodated eyes. The thicknesses and profiles of the lenses are also determined., Conclusions: The lens refractive index varies substantially from individual eye to individual eye, not only along the central ray pathway but also for the lens refractive index function across the lens diameter. Ray-traceable Scheimpflug imaging-equipped AS-OCT is useful for testing the refractive index of lenses in the human eye in vivo ., Competing Interests: Conflict of Interest Disclosure: The author has reported no conflict of interest., (Copyright © 2023 American Academy of Optometry.)

A design of a multiband terahertz (THz) metamaterial biosensor for early cancer detection is proposed. The THz biosensor composed of several arc-shaped connecting parts operates at three different frequencies, and the absorptivity of the three resonant frequencies exceeds 99% in free space. In this work, we analyzed the absorption spectrum and polarization independence under different design parameters, improved the performance of the sensor by adjusting the absorption characteristics of the sensor, and gave the calculation results. Additionally, we studied the influence of the refractive index and thickness of different samples on the sensor, and theoretically calculated the sensitivity of the sensor to basal cells, breast cells, cervical cells, and their corresponding cancer cells. The result shows that the maximum sensitivity of the sensor can reach 642.5 GHz/RIU, which is much higher than the reported biosensors. Therefore, the proposed THz sensor has great potential in early detection and early warning of cancer.

A beta-cyclodextrin (β-CD) based optic-fiber microfiber biosensor for the detection of cholesterol concentration is propose and experimentally demonstrated. As an identifying substance, β-CD is immobilized on the fiber surface for cholesterol reaction to form an inclusion complex. When the surface refractive index (RI) change is cause because of capturing the complex cholesterol (CHOL), the proposed sensor translates RI change into a macroscopic wavelength drift in the interference spectrum. The microfiber interferometer has a high RI sensitivity of 1251 nm/RIU and a low-temperature sensitivity of -0.019 nm/°C. This sensor can rapidly detect cholesterol in the concentration range of 0.001 to 1 mM and has a sensitivity of 12.7 nm/(mM) in the low concentration range of 0.001 to 0.05 mM. Finally, the characterization by infrared spectroscopy shows that the sensor can indeed detect cholesterol. This biosensor has a few strong advantages of high sensitivity and good selectivity, which expects great potential in biomedical applications., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

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

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

Background: High molecular weight (MW) synthetic colloids interfere with refractometry. The effect of low MW synthetic colloids on refractometry is unknown. Objectives: To investigate the effect of 6% hydroxyethyl starch 130/0.4 (HES) and 4% succinylated gelatin (GELO) on the refractometric measurement of total plasma protein (TPP) and colloid osmotic pressure (COP) in canine plasma. Methods: Heparinized plasma from 10 dogs was diluted with 0.9% saline (NaCl), HES, and GELO in ratios of plasma:fluid, 9:1, 8:2, 7:3, 6:4, and 5:5. The biuret TPP (TPPb), refractometric TPP (TPPr), and COP assays were performed for all dilutions. Agreement (bias, 95% limits of agreement (LOA)) was tested between the TPPb (NaCl) and the TPPr of the NaCl, HES, and GELO plasma dilutions, and between the TPPb (NaCl) and the TPPb of the HES and GELO plasma dilutions. Results: A small bias (0.06 g/dL, 95% LOA −0.51 to 0.39 g/dL) existed between TPPb (NaCl) and TPPr (NaCl). A large bias was found between TPPb (NaCl) and TPPr (HES) (1.38 g/dL, 95% LOA 0.30 to 3.10 g/dL), and TPPr (GELO) (1.18 g/dL, 95% LOA 0.53 to 2.88 g/dL). A small bias was found between TPPb (NaCl) and TPPb (HES) (0.08 g/dL, 95% LOA −2.04 to 2.20 g/dL), and a large bias was found between TPPb (NaCl) and TPPb (GELO) (1.00 g/dL, 95% LOA −0.59 to 2.60 g/dL). Increasing overestimation of TPPb (NaCl) by TPPr (HES and GELO) and TPPb (GELO) occurred with increasing colloid volumes. Conclusions: HES and GELO interfered with TPPr, and GELO also interfered with TPPb, in vitro. These variables should be interpreted with caution for dogs that have received these synthetic colloids. [ABSTRACT FROM AUTHOR]

Twenty-eight warmblood mares were monitored during their late pregnancy in the Teaching Hospital of Ghent University. The reliability of two commercial assays (enzyme immunoassay and glutaraldehyde coagulation test) used for determining the IgG concentrations of their newborn foals was tested. Mammary secretions were examined at the time of foaling (T0), and then 4 (T1) and 8 (T2) hours after foaling by refractometry and electrophoresis. The foals' blood IgG levels were measured at T1 and T2 as a routine clinical diagnostic examination using two different commercial test kits (SNAP Foal Ig and Gamma-Check E) and T0, T1 and T2 samples were stored (at −18 °C) for immunoglobulin (Ig) determination by electrophoresis. Differences between the results of refractometry and electrophoresis occurred in 27.8% of the colostrum analyses. Some serum IgG could be detected immediately post partum (T0) in 75% of the foals, and 42.82% of the newborn foals acquired a serum concentration of more than 800 mg/dl IgG within 8 h of birth. Compared to the electrophoresis, the glutaraldehyde test scored better (85%) than the enzyme immunoassay (74%), although both are accurate and safe to use since they clearly distinguish between safe and unsafe IgG concentrations. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

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

Mass transport in (drug + cyclodextrin) solutions is investigated by using Taylor dispersion technique, monitored by differential refractometry, to measure ternary mutual diffusion in aqueous solutions of {L-dopa + (NaSO 3 ) n -β-CD} (the sodium salt of sulfated β-cyclodextrin). The values of the binary mutual diffusion coefficients of both aqueous L-dopa and aqueous (NaSO 3 ) n -β-CD solutions are close to each other differing only by a few per cent units. As a result, the eigenvalues for the matrix of the ternary D ik diffusion coefficients for aqueous {L-dopa(1) + (NaSO 3 ) n -β-CD(2)} solutions are nearly identical, and the numerical analysis of the Taylor dispersion data may be ill-conditioned in view of the unreliable data obtained from their analysis. To overcome these difficulties, the pseudo-binary diffusion approximation is used to evaluate in a simple way this ternary system. The pseudo-binary diffusion coefficient values found, D p1 and D p2 , are very close to the binary diffusion ones, being the cross-coefficients approached zero, within the experimental error. From the obtained results, and under the circumstances of this study, we may deduct that no interaction between L-dopa and NaSO 3 ßCD was determined. [ABSTRACT FROM AUTHOR]

The accurate measurements of droplet temperature, size and evaporation rate are of great importance to characterize the heat and mass transfer during evaporation/condensation processes. The nanoscale size change of a micron-sized droplet exactly describes its transient mass transfer, but is difficult to measure because it is smaller than the resolutions of current size measurement techniques. The Phase Rainbow Refractometry (PRR) technique is developed and applied to measure droplet temperature, size and transient size changes and thereafter evaporation rate simultaneously. The measurement principle of PRR is theoretically derived, and it reveals that the phase shift of the time-resolved ripple structures linearly depends on, and can directly yield, nano-scale size changes of droplets. The PRR technique is first verified through the simulation of rainbows of droplets with changing size, and results show that PRR can precisely measure droplet refractive index, absolute size, as well as size change with absolute and relative errors within several nanometers and 0.6%, respectively, and thus PRR permits accurate measurements of transient droplet evaporation rates. The evaporations of flowing single n-nonane droplet and mono-dispersed n-heptane droplet stream are investigated by two PRR systems with a high speed linear CCD and a low speed array CCD, respectively. Their transient evaporation rates are experimentally determined and quantitatively agree well with the theoretical values predicted by classical Maxwell and Stefan–Fuchs models. With the demonstration of evaporation rate measurement of monocomponent droplet in this work, PRR is an ideal tool for measurements of transient droplet evaporation/condensation processes, and can be extended to multicomponent droplets in a wide range of industrially-relevant applications. [ABSTRACT FROM AUTHOR]

Planar and multilayered photonic devices offer unprecedented opportunities in biological and chemical sensing due to strong light-matter interactions. However, uses of rigid substances such as semiconductors and dielectrics confront photonic devices with issues of biocompatibility and a mechanical mismatch for their application on humid, uneven, and soft biological surfaces. Here, we report that favorable material traits of natural silk protein led to the fabrication of an ultra-thin, conformal, and water-permeable (hydratable) metal-insulator-metal (MIM) color absorber that was mapped on soft, curved, and hydrated biological interfaces. Strong absorption was induced in the MIM structure and could be tuned by hydration and tilting of the sample. The transferred MIM color absorbers reached the exhibition of a very strong resonant absorption in the visible and near infra-red ranges. In addition, we demonstrated that the conformal resonator could function as a refractometric glucose sensor applied on a contact lens. [ABSTRACT FROM AUTHOR]

Modifying material properties in simple macromolecules such as polyethylene (PE) is achieved by different connection modes of ethylene monomers resulting in a plurality of possible topologies-from highly linear to dendritic species. However, the challenge still lies within the experimental identification of the topology and conformation of the isolated macromolecules because of their low solubility, which demands methods with specific solvents and high operating temperatures. Additionally, a separation technique has to be coupled to different detection methods to meet the specific demands of the respective characterization goal. In this work, we report a quadruple-detector high temperature size exclusion chromatography (HT-SEC) system which contains online multiangle laser light scattering, dynamic light scattering, differential viscometry, and differential refractometry detectors. Quadruple-detector HT-SEC was successfully applied to explore the full range of physical parameters of various PE samples with different branching topologies ranging from highly linear macromolecules, polymers with moderate level of branching, to highly branched PEs with hyperbranched structure. This method is a useful tool not only to investigate molecular weight, mass distribution, and size but also to enable access to important factors which describe the conformation in dilute solution and branching density. [ABSTRACT FROM AUTHOR]

The phase behavior of fats is mainly determined using DSC. Here, the application of temperature modulated optical refractometry (TMOR) is examined to monitor the phase transitions of palm oil with different degrees of saturation. Studying the phase behavior by both methods revealed systematic differences. At identical scan rates, TMOR yielded up to 2 °C higher crystallization temperatures and identified consistently lower temperatures for melting phenomena. Because the prism serves as heating surface and defines the sample volume considered for the measurement a more direct heat transfer with TMOR is assumed. The sample depth above the prism relevant for the determination is only one micron. Hence, a direct heat transfer is ensured and thermal lag is practically eliminated causing the above‐mentioned differences. Because the TMOR signal is averaged over a defined prism surface area data for inhomogeneous samples can be generated. Although actual values for thermal expansion coefficients appear meaningless the combination of the TMOR signals allows to accurately determine the relevant phase transitions. The identification of different polymorphic forms and levels of solids in palm oil will be studied prospectively building on the promising results reported to identify if TMOR can become a valuable extension of the fat technologists' toolbox. Practical Applications: The new temperature modulated optical refractometry can extend the mainly used differential scanning calorimetry. It works highly accurate at small scan rates (<5 °C min−1) in comparison to the DSC. The new method can provide a deeper insight into samples during heating and cooling due to additional temperature undulation as well as the possibility to perform quasi‐isothermal measurements. It is possible to investigate the crystallization and melting behavior of fats with the new temperature modulated optical refractometry (TMOR). An undulated temperature is applied and the time‐delayed answer of the refractive index is measured. Subsequently, the real and imaginary part of the thermal expansion coefficient α are calculated based on the refractive index of the sample and the occurring phase shift. A plot of the real and imaginary part against the temperature leads to peaks at the phase transition temperatures and a resulting thermogram for the sample. [ABSTRACT FROM AUTHOR]

The authors report on the realization of a novel methodology for refractometry—GAs modulation refractometry (GAMOR)—that decreases the influence of drifts in Fabry Perot cavity refractometry. The instrumentation is based on a dual Fabry-Perot cavity refractometer in which the beat frequency between the light fields locked to two different cavities, one measurement and one reference cavity, is measured. The GAMOR methodology comprises a process in which the measurement cavity sequentially is filled and evacuated while the reference cavity is constantly evacuated. By performing beat frequency measurements both before and after the finite-pressure measurement, zero point references are periodically created. This opens up for high precision refractometry under nontemperature-stabilized conditions. A first version of an instrumentation based on the GAMOR methodology has been realized and its basic performance has been scrutinized. The refractometer consists of a Zerodur cavity-block and tunable narrow linewidth fiber lasers operating within the C34 communication channel (i.e., around 1.55 μm) at which there are a multitude of fiber coupled off-the-shelf optical, electro-optic, and acousto-optic components. The system is fully computer controlled, which implies it can perform unattended gas assessments over any foreseeable length of time. When applied to a system with no active temperature stabilization, the GAMOR methodology has demonstrated a 3 orders of magnitude improvement of the precision with respect to conventional static detection. When referenced to a dead weight pressure scale the instrumentation has demonstrated assessment of pressures in the kilo-Pascal range (4303 and 7226 Pa) limited by white noise with standard deviations in the 3.2 N − 1 / 2 – 3.5 N − 1 / 2 mPa range, where N is the number of measurement cycles (each being 100 s long). For short measurement times (up to around 103 s), the system exhibits a ( 1 σ ) total relative precision of 0.7 (0.5) ppm for assessment of pressures in the 4 kPa region and 0.5 (0.4) ppm for pressures around 7 kPa, where the numbers in parentheses represent the part of the total noise that has been attributed to the refractometer. As long as the measurement procedure is performed over short time scales, the inherent properties of the GAMOR methodology allow for high precision assessments by the use of instrumentation that is not actively temperature stabilized or systems that are affected by outgassing or leaks. They also open up for a variety of applications within metrology; e.g., transfer of calibration and characterization of pressure gauges, including piston gauges. [ABSTRACT FROM AUTHOR]

The paper is devoted to investigation of physico-chemical properties of the C 70 - l -lysine derivative aqueous solutions. Within the framework of our investigation, we have studied the concentration dependences of density, average molar volume and partial molar volumes of the solution components, specific and molar conductivities, dissociation constant, apparent degree of dissociation, ζ – potential as well as concentration dependences of the C 70 - l -lysine associates size distribution in aqueous solutions. Additionally we have used the semi-empirical VD-AS (Virial Decomposition Asymmetric Model) model and calculated the excess thermodynamic functions of solutions and solution components. [ABSTRACT FROM AUTHOR]

The results of complex studies of a possibility of the rapid analysis of solutions using a spectroscopic system based on a hollow-core photonic-crystal fiber are presented. Pharmaceutical preparations of vitamins B and C from various manufacturers were selected as test samples. The transformation of the transmission spectra of the fiber after filling hollow channels with an analyte solution was observed in the wavelength region of 350-1100 nm, depending on the type of the vitamin, producer, and concentration. Comparative quantitative estimates of the sensitivity, resolution, and error in determining the concentration of solutions are given. To increase the functionality of the spectroscopic system, it is suggested to use known chemometric methods and algorithms. [ABSTRACT FROM AUTHOR]

A slab waveguide structure consisting of five layers is studied for optical sensing applications. The five-layer waveguide structure has a guiding dielectric film, two left-handed material (LHM) layers and two dielectric layers as a substrate and a cladding. The dispersion relation and the sensitivity to any change in the index of the analyte layer are derived. The sensitivity is explored with different parameters of the structure. It is found that the sensitivity of the proposed structure can be significantly improved with the increase of the index of the guiding layer and the decrease of the permittivity of the LHM layers. Moreover, it can be also improved with the increase of the thickness of the LHM layers. [ABSTRACT FROM AUTHOR]

Refractometry is a classic analytical method in analytical chemistry and biosensing. By integrating advanced micro- and nano-optical systems with well-developed microfluidics technology, optofluidics are shown to be a powerful, smart and universal platform for refractive index sensing applications. This paper reviews recent work on optofluidic refractometers based on different sensing mechanisms and structures (e.g., photonic crystal/photonic crystal fibers, waveguides, whisper gallery modes and surface plasmon resonance), and traces the performance enhancement due to the synergistic integration of optics and microfluidics. A brief discussion of future trends in optofluidic refractometers, namely volume sensing and resolution enhancement, are also offered. [ABSTRACT FROM AUTHOR]

Characterization of spermatozoon viability is a common test in treating infertility. Recently, it has been shown that label-free, phase-sensitive imaging can provide a valuable alternative for this type of assay. We employ spatial light interference microscopy (SLIM) to perform high-accuracy single-cell phase imaging and decouple the average thickness and refractive index information for the population. This procedure was enabled by quantitative-phase imaging cells on media of two different refractive indices and using a numerical tool to remove the curvature from the cell tails. This way, we achieved ensemble averaging of topography and refractometry of 100 cells in each of the two groups. The results show that the thickness profile of the cell tail goes down to 150 nm and the refractive index can reach values of 1.6 close to the head. [ABSTRACT FROM AUTHOR]

High intensity ultrasonication (US) alone or in combination with chemical immersion treatments of lactic acid (3% LA), sodium decanoate (3% SD) and trisodium phosphate (10% TSP) were investigated to reduce populations of Campylobacter jejuni and spoilage organisms in raw chicken. Different experimental conditions were used including a range of temperatures (4 °C, 25 °C and 54 °C) and exposure times (1, 2 and 3 min). All combination treatments significantly reduced C. jejuni compared to their individual treatments while only the combination US + SD significantly reduced Total Viable Count (TVC). Multiple linear regression predicted bacterial reductions resulting from changing treatment, temperature and time or each group of microorganisms. Increasing temperature from 4 °C to 54 °C would enhance C. jejuni , TVC and Total Enterobacteriaceae Count (TEC) reductions by 0.73, 1.02 and 1.37 log 10 cfu/g respectively. Increasing time from 1 to 3 min enhanced bacterial dependent of C. jejuni and TEC by 0.49 and 0.31 log 10 cfu/g respectively. Industrial relevance. This study demonstrates the potential application of high intensity ultrasomication alone or in combination with chemical treatments to reduce bacterial contamination of chicken carcasses. Different tempretures and times were investigated to optimize the most effective treatments conditions in chicken abattoirs. [ABSTRACT FROM AUTHOR]

This work reports a novel structure for a Fabry--Pérot micro cavity that combines the highest reported quality factor for an on-chip Fabry--Pérot resonator that exceeds 9800, and a very high sensitivity for an on-chip volume refractometer based on a Fabry--Pérot cavity that is about 1000 nm/refractive index unit (RIU). The structure consists of two cylindrical Bragg micromirrors that achieve confinement of the Gaussian beam in the plan parallel to the chip substrate, while for the perpendicular plan, external fiber rod lenses (FRLs) are placed in the optical path of the input and the output of the cavity. This novel structure overcomes number of the drawbacks presented in previous designs. The analyte is passed between the mirrors, enabling its detection from the resonance peak wavelengths of the transmission spectra. Mixtures of ethanol and deionized (DI)-water with different ratios are used as analytes with different refractive indices to exploit the device as a micro-opto-fluidic refractometer. The design criteria are detailed and the modeling is based on Gaussian-optics equations, which depicts a scenario closer to reality than the usually used ray-optics modeling. [ABSTRACT FROM AUTHOR]