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Micromachines Mar 2018Refractometry is a classic analytical method in analytical chemistry and biosensing. By integrating advanced micro- and nano-optical systems with well-developed... (Review)
Review
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.
PubMed: 30424070
DOI: 10.3390/mi9030136 -
Experimental Eye Research Apr 2022Emmetropization is affected by the temporal parameters of visual stimulation and the spectral composition of light, as well as by autonomic innervation. The goal of the...
Emmetropization is affected by the temporal parameters of visual stimulation and the spectral composition of light, as well as by autonomic innervation. The goal of the current experiments is to test the hypothesis that different types of visual stimulation interact with ocular innervation in the process of emmetropization. For that, selective lesions of the autonomic nervous system were performed in chickens: involving transection of parasympathetic input to the eye from either the ciliary ganglion, innervating accommodation and pupil responses (CGX; n = 32), or pterygopalatine ganglion, innervating choroidal blood vessels and cornea (PPGX; n = 26). After 1 week of recovery, chicks were exposed to sinusoidally modulated light (3 days, 2 Hz, 680 lux) that was either achromatic (black to white [RGB], or black to yellow [RG]), or chromatic (blue to yellow [B/Y] or red to green [R/G]). Exposure to light stimulation was followed by ocular biometry (Lenstar and a Hartinger refractometer). Surgical conditions revealed a small reduction in anterior chamber depth with CGX but no other significant changes in ocular biometry/refraction under standard light conditions. With RGB achromatic stimulation, CGX eyes produced an effect on ocular components, with a further reduction in anterior chamber depth and an increase in vitreous chamber depth, while RG stimulation showed no effect. No effect was detected in PPGX under both achromatic protocols. With chromatic stimulation, CGX with R/G modulation increased eye length, while PPGX with B/Y modulation decreased eye length. We conclude that the two different types of parasympathetic innervations have antagonistic effects on eye growth and the anterior eye when challenged with the appropriate stimulus, with possible implications for the role of choroidal blood flow in emmetropization.
Topics: Accommodation, Ocular; Animals; Chickens; Choroid; Emmetropia; Eye; Refraction, Ocular
PubMed: 35120871
DOI: 10.1016/j.exer.2022.108964 -
Optics Express Mar 2022This work presents the implementation of a thermo-refractometer, which integrates the measurement of both refractive index and temperature in a single optical fiber...
This work presents the implementation of a thermo-refractometer, which integrates the measurement of both refractive index and temperature in a single optical fiber structure. To this purpose, a lossy mode resonance (LMR)-based refractometer is obtained by means of the deposition of a titanium dioxide (TiO) thin film onto a side-polished (D-shaped) single mode fiber. Measurement and subsequent temperature compensation are achieved by means of a fiber Bragg grating (FBG) inscribed in the core of the D-shaped region. The LMR wavelength shift is monitored in transmission while the FBG (FBG peak at 1533 nm) displacement is observed in reflection. The LMR is sensitive to both the surrounding refractive index (SRI), with a sensitivity of 3725.2 nm/RIU in the 1.3324-1.3479 range, and the temperature (- 0.186 nm/°C); while the FBG is only affected by the temperature (32.6 pm/°C in the 25°C - 45°C range). With these values, it is possible to recover the SRI and temperature variations from the wavelength shifts of the LMR and the FBG, constituting a thermo-refractometer, where it is suppressed the effect of the temperature over the refractometer operation, which could cause errors in the fourth or even third decimal of the measured SRI value.
PubMed: 35473056
DOI: 10.1364/OE.450316 -
Sensors (Basel, Switzerland) Mar 2022Quality assessment of fruits, vegetables, or beverages involves classifying the products according to the quality traits such as, appearance, texture, flavor, sugar... (Review)
Review
Quality assessment of fruits, vegetables, or beverages involves classifying the products according to the quality traits such as, appearance, texture, flavor, sugar content. The measurement of sugar content, or Brix, as it is commonly known, is an essential part of the quality analysis of the agricultural products and alcoholic beverages. The Brix monitoring of fruit and vegetables by destructive methods includes sensory assessment involving sensory panels, instruments such as refractometer, hydrometer, and liquid chromatography. However, these techniques are manual, time-consuming, and most importantly, the fruits or vegetables are damaged during testing. On the other hand, the traditional sample-based methods involve manual sample collection of the liquid from the tank in fruit/vegetable juice making and in wineries or breweries. Labour ineffectiveness can be a significant drawback of such methods. This review presents recent developments in different destructive and nondestructive Brix measurement techniques focused on fruits, vegetables, and beverages. It is concluded that while there exist a variety of methods and instruments for Brix measurement, traits such as promptness and low cost of analysis, minimal sample preparation, and environmental friendliness are still among the prime requirements of the industry.
Topics: Beverages; Carbohydrates; Fruit; Refractometry; Vegetables
PubMed: 35336461
DOI: 10.3390/s22062290 -
Scientific Reports Jul 2022In this paper, a comparative analysis between the hand-held refractometer and other methods (TKN and CHNS) was accomplished for the estimation of nitrogen percentage...
In this paper, a comparative analysis between the hand-held refractometer and other methods (TKN and CHNS) was accomplished for the estimation of nitrogen percentage (N%) in urea, nano urea fertilizer, and diesel exhaust fluid (DEF) solution. In order to compare the performance of all methods/devices, the detection of N% in different concentrations of urea, nano urea, and DEF were evaluated in terms of their linearity. The most important finding of this study was that the refractometer-based device revealed a good linear coefficient up to 40% urea solution (R = 0.99918) among other approaches, which means the estimation of N% is more close to the theoretical value. Moreover, the refractometer has detected the urea, nano urea, and DEF samples within 3 s which were quite fast as compared to other tested methods and no requirement of any chemicals during the sample preparation and analyses. Thus, the finding of this study suggests that a hand-held urea refractometer-based portable device can be used for onsite N% determination by the fertilizer and DEF manufacturing industries and their customers due to its low cost, low power requirement, reliable estimation, rapid N% detection, and its environmental suitability.
Topics: Fertilizers; Nitrogen; Refractometry; Urea
PubMed: 35810201
DOI: 10.1038/s41598-022-15736-z -
Animals : An Open Access Journal From... Dec 2021The immunoglobulin concentration in bovine colostrum should be measured to ensure feeding with sufficient immunoglobulins (≥50 mg immunoglobulin G mL). Adequate... (Review)
Review
The immunoglobulin concentration in bovine colostrum should be measured to ensure feeding with sufficient immunoglobulins (≥50 mg immunoglobulin G mL). Adequate feeding prevents diseases, promotes development, and has a positive influence on the adult animal. Indirect and direct measurement methods are available for this purpose. Direct measurement methods cannot be easily used in practice; therefore, farmers use indirect methods such as a colostrometer and a refractometer. Many factors influence the immunoglobulin concentration of colostrum; some of them have already been intensively researched. In particular, lactation and temporal aspects play an essential role. Newer aspects such as dry period, seasonal influences, and genetics are gaining importance, but their impact on immunoglobulin content has not been sufficiently investigated. Developments are still needed, especially in data management. This review analyzes the outcome of different studies on the indirect and direct measurement methods and discusses different factors influencing the immunoglobulin concentration of bovine colostrum.
PubMed: 34944362
DOI: 10.3390/ani11123587 -
Current Protocols in Protein Science Aug 2014Well-characterized membrane protein detergent complexes (PDC) that are pure, homogenous, and stable, with minimized excess detergent micelles, are essential for... (Review)
Review
Well-characterized membrane protein detergent complexes (PDC) that are pure, homogenous, and stable, with minimized excess detergent micelles, are essential for functional assays and crystallization studies. Procedural steps to measure the mass, size, shape, homogeneity, and molecular composition of PDCs and their host detergent micelles using size-exclusion chromatography (SEC) with a Viscotek Tetra Detector Array (TDA; absorbance, refractive index, light scattering, and viscosity detectors) are presented in this unit. The value of starting with a quality PDC sample, the precision and accuracy of the results, and the use of a digital benchtop refractometer are emphasized. An alternate and simplified purification and characterization approach using SEC with dual absorbance and refractive index detectors to optimize detergent and lipid concentration while measuring the PDC homogeneity is also described. Applications relative to purification and characterization goals are illustrated as well.
Topics: Chromatography, Gel; Detergents; Membrane Proteins; Micelles; Refractometry
PubMed: 25081744
DOI: 10.1002/0471140864.ps2910s77 -
Journal of Veterinary Diagnostic... Jan 2020Urine specific gravity (USG), which is usually measured by refractometry, is an important indicator of renal concentrating ability. Few studies have evaluated...
Urine specific gravity (USG), which is usually measured by refractometry, is an important indicator of renal concentrating ability. Few studies have evaluated refractometers with separate scales for canine and feline urine. Variables such as protein content or storage time may influence the USG. We compared the effects of measuring USG with a refractometer with single or separate scales for canine and feline urine, investigated inter- and intra-observer variability, and measured agreement between whole urine and supernatant. We evaluated the correlation between USG and osmolality, the influence of urinary protein on USG and osmolality, and the impact of storage time up to 6 mo. We examined 252 canine and 126 feline samples. Bland-Altman analysis revealed higher USG values of the single-scale refractometer than the dual-scale refractometer, with a mean difference (bias) of < 0.001 for canine and 0.003 for feline specimens. Inter- and intra-observer variability were acceptable. Good agreement was shown between USG of whole urine and supernatant. Correlations between USG and osmolality were excellent (0.98-0.99, < 0.001). Proteinuria up to 1 g/L had no major impact on USG or osmolality. Storage time had no significant effect on USG. The difference between the refractometers is clinically irrelevant, and the use of a refractometer with separate feline and canine scales is unnecessary. Whole urine and supernatant stored up to 6 mo can both be used for USG measurement. The influence of proteinuria <1 g/L on USG and osmolality is negligible.
Topics: Animals; Cats; Dogs; Osmolar Concentration; Refractometry; Specific Gravity; Urinalysis
PubMed: 31876254
DOI: 10.1177/1040638719896785