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1.
J Vet Diagn Invest ; 32(1): 36-43, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31876254

RESUMO

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, p < 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.


Assuntos
Gatos/urina , Cães/urina , Refratometria/veterinária , Urinálise/veterinária , Animais , Concentração Osmolar , Refratometria/instrumentação , Gravidade Específica , Urinálise/instrumentação
2.
Acta Vet Scand ; 61(1): 59, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31805965

RESUMO

BACKGROUND: There is an increased interest in using digital refractometers to indirectly assess colostrum quality of dairy cattle, but knowledge on diagnostic accuracy for Norwegian Red dairy cows is lacking. Recent research has indicated a profound variability in the colostrum quality among dairy cows and herds in Norway. The aim of this study was to evaluate the diagnostic test sensitivity and specificity of a digital refractometer (Brix refractometer) at different cut-offs in Brix% for detection of colostrum of high quality (> 50 g/L) defined by the gold standard single radial immunodiffusion (IgG g/L). Furthermore, we aimed to identify possible associations between selected herd and cow-level management factors and colostrum IgG-levels in Norwegian Red dairy cows. RESULTS: Median colostrum IgG level across 167 cows from 19 herds was 35.0 g/L, ranging from 5 to 129 g/L. Mean Brix% (± SD) was 19.7 ± 4.12%, ranging from 10.1 to 30.5. Most samples (72.5%) had inferior quality as compared to the international standard of 50 g/L. Brix% and IgG in colostrum were strongly correlated (r = 0.71, P < 0.001). A Brix cut-off of 22%, which is currently recommended, yielded a sensitivity of (95% CI) 69.4% (54.6-81.7) and a specificity of 83.1% (75.0-89.3) for identifying colostrum with high quality (> 50 g/L). The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with low quality compared to cows in parities four and later. CONCLUSIONS: The agreement between colostrum IgG and Brix% is good. However, the diagnostic test evaluation indicates suboptimal performance in identifying high vs. low colostrum quality in this population, possibly related to a high proportion of the samples with < 50 g/L IgG. The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with lower quality. Future research should investigate colostrum and serum IgG levels which best prevent calf illness under Norwegian conditions.


Assuntos
Colostro/fisiologia , Indústria de Laticínios , Testes Diagnósticos de Rotina/veterinária , Imunoglobulina G/análise , Refratometria/veterinária , Animais , Bovinos , Indústria de Laticínios/métodos , Testes Diagnósticos de Rotina/métodos , Feminino , Refratometria/instrumentação , Sensibilidade e Especificidade
3.
Biosens Bioelectron ; 144: 111693, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31539719

RESUMO

Biosensor technology is an active field of research and development presenting rapid progress in recent decades, and the subfield of optical biosensors based on refractometric sensing schemes has developed dramatically during this time. This review focuses on advances in the refractometric sensing-based guided-wave optical biosensors particularly in the last two decades. It starts with a concise discussion on the underlying principles of label-free refractometric biosensor. Subsequently, advances in biosensor design, especially the transducer configuration and the integration of the sensing device are reviewed, highlighting the challenges and efforts dedicated to improving this technology. Various surface functionalization strategies designed to produce well-defined and reproducible surface properties are introduced for evaluation. Refractometric sensing scheme-based optical biosensors have found versatile applications varying from environmental monitoring and food safety to clinical diagnostics, together with advances in these applications and others are described. This paper concludes with a brief discussion on the outlook for integrating biosensors with emerging technologies.


Assuntos
Técnicas Biossensoriais/métodos , Óptica e Fotônica/métodos , Refratometria/métodos , Técnicas Biossensoriais/instrumentação , Técnicas Biossensoriais/tendências , Humanos , Óptica e Fotônica/instrumentação , Óptica e Fotônica/tendências , Patologia Molecular/tendências , Refratometria/instrumentação , Refratometria/tendências
4.
J Synchrotron Radiat ; 26(Pt 5): 1514-1522, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31490139

RESUMO

Free-electron lasers (FELs) based on superconducting accelerator technology and storage ring facilities operate with bunch repetition rates in the MHz range, and the need arises for bunch-by-bunch electron and photon diagnostics. For photon-pulse-resolved measurements of spectral distributions, fast one-dimensional profile monitors are required. The linear array detector KALYPSO (KArlsruhe Linear arraY detector for MHz-rePetition rate SpectrOscopy) has been developed for electron bunch or photon pulse synchronous read-out with frame rates of up to 2.7 MHz. At the FLASH facility at DESY, a current version of KALYPSO with 256 pixels has been installed at a grating spectrometer as online diagnostics to monitor the pulse-resolved spectra of the high-repetition-rate FEL pulses. Application-specific front-end electronics based on MicroTCA standard have been developed for data acquisition and processing. Continuous data read-out with low latency in the microsecond range enables the integration into fast feedback applications. In this paper, pulse-resolved FEL spectra recorded at 1.0 MHz repetition rate for various operation conditions at FLASH are presented, and the first application of an adaptive feedback for accelerator control based on photon beam diagnostics is demonstrated.


Assuntos
Refratometria/instrumentação , Elétrons , Desenho de Equipamento , Lasers , Fótons , Espalhamento de Radiação , Síncrotrons
5.
J Synchrotron Radiat ; 26(Pt 5): 1572-1581, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31490146

RESUMO

An X-ray amplitude-splitting interferometer based on compound refractive lenses, which operates in the reflection mode, is proposed and realized. The idea of a reflecto-interferometer is to use a very simplified experimental setup where a focused X-ray beam reflected from parallel flat surfaces creates an interference pattern in a wide angular range. The functional capabilities of the interferometer were experimentally tested at the European Synchrotron Radiation Facility (ESRF) ID06 beamline in the X-ray energy range from 10 keV to 15 keV. The main features of the proposed approach, high spatial and temporal resolution, were demonstrated experimentally. The reflections from free-standing Si3N4 membranes, gold and resist layers were studied. Experimentally recorded interferograms are in good agreement with our simulations. The main advantages and future possible applications of the reflecto-interferometer are discussed.


Assuntos
Interferometria/instrumentação , Lentes , Refratometria/instrumentação , Desenho de Equipamento , Síncrotrons , Raios X
6.
J Dairy Sci ; 102(8): 7459-7463, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31202644

RESUMO

Transition milk is a source of immunoglobulin G (IgG) and could potentially be used to provide calves with passive immunity, when the IgG concentration is ≥50 g/L. Assessment of IgG concentrations in transition milk would be required before feeding and could be conducted using cow-side tests such as refractometers. Currently, limited information is available on the ability of refractometers to assess transition milk quality. We hypothesized that digital refractometry could be used to provide an accurate cow-side assessment of IgG concentrations in colostrum and transition milk, and IgG concentration in colostrum and one or more transition milking in an Irish herd is >50 g/L. The objectives of this study were to determine the IgG concentrations in colostrum and first, second, third, fourth, and fifth transition milk, and determine the utility of a digital refractometer in assessing quality of colostrum and transition milk produced by cows in a pasture-based dairy production system. A convenient sample of 75 dairy cows were enrolled. Colostrum and transition milk IgG concentrations were determined by radial immunodiffusion and refractometry. Sensitivity and specificity of the refractometer were determined and cut-off points that maximized sensitivity and specificity were determined using receiver operating characteristic curves. Median (range) IgG concentrations in colostrum and first, second, third, fourth, and fifth milking were 99.6, 43.5, 12.5, 5.3, 1.9, and 1.8 g/L, respectively. The sensitivity (0.8-1) of digital refractometry in identifying samples with low IgG concentrations in colostrum, first, second, and third transition milk was acceptable. In contrast, digital refractometry was not useful for assessing IgG concentrations in the fourth and fifth milking due to low IgG concentrations.


Assuntos
Colostro/imunologia , Imunoglobulina G/análise , Refratometria/veterinária , Animais , Bovinos , Feminino , Imunodifusão/veterinária , Leite , Gravidez , Curva ROC , Refratometria/instrumentação , Sensibilidade e Especificidade
7.
Biosens Bioelectron ; 141: 111396, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31195197

RESUMO

Mode volume overlap factor is one of the parameters determining the sensitivity of a sensor. In past decades, many approaches have been proposed to increase the mode volume overlap. As the increased mode volume overlap factor results in reduced mode confinement, the maximum value is ultimately determined by the micro- and nano-structure of the refractive index distribution of the sensing devices. Due to the asymmetric index profile along the vertical direction on silicon-on-insulator platform, further increasing the sensitivity of subwavelength grating metamaterial (SGM) waveguide based sensors is challenging. In this paper, we propose and demonstrate pedestaled SGM which reduces the asymmetricity and thus allows further increasing the interaction between optical field and analytes. The pedestal structure can be readily formed by a controlled undercut etching. Both theoretical analysis and experimental demonstration show a significant improvement of sensitivity. The bulk sensitivity and surface sensitivity are improved by 28.8% and 1000 times, respectively. The detection of streptavidin at a low concentration of 0.1 ng/mL (∼1.67 pM) is also demonstrated through real-time monitoring of the resonance shift. A ∼400 fM streptavidin limit of detection is expected with a 0.01nm resolution spectrum analyzer based on the real-time measurement of streptavidin detection results from two-site binding model fitting.


Assuntos
Técnicas Biossensoriais/instrumentação , Refratometria/instrumentação , Algoritmos , Desenho de Equipamento , Silício/química , Estreptavidina/análise
8.
J. optom. (Internet) ; 12(2): 99-110, abr.-jun. 2019. tab, graf
Artigo em Inglês | IBECS | ID: ibc-180890

RESUMO

Purpose: To determine the agreement and validity of keratometric measurements in children with the Nidek ARK-510A auto-refractokeratometer compared to rotating Scheimpflug imaging with Pentacam and biograph with Lenstar LS 900. Methods: This study was conducted on 5620 schoolchildren aged 6-12 years in Shahroud, Iran. Minimum and maximum keratometry values and corneal astigmatism magnitude were compared by calculation of Paired difference, interclass correlation coefficient, and 95% limits of agreement (LoA) between devices. Results: After applying the exclusion criteria, 4215 right eyes were enrolled into the study. Mean minimum keratometry with Nidek ARK-510A, Pentacam, and Lenstar was 43.13 ± 1.51, 43.14 ± 1.48, and 42.87 ± 1.46 diopters (D), respectively, and mean maximum keratometry was 43.97 ± 1.59, 44.00 ± 1.56, and 43.75 ± 1.54D, respectively. Nidek ARK-510A overestimated minimum and maximum keratometry by 0.25 ± 0.37 and 0.22 ± 0.41, respectively, compared to Penatcam. The LoA between Nidek ARK-510A and Pentacam for minimum and maximum keratometry measurements were -0.98 to 0.47D and −1.02 to 0.57D, respectively. The LoA between Nidek ARK-510A and Lenstar for minimum and maximum keratometry measurements were -0.70 to 0.72D and -0.79 to 0.85D, respectively. The agreement between devices was best in emmetropes, worst in hyperopes. For astigmatic vector components, the agreements between devices were poor but best agreement was between Nidek ARK-510A and Pentacam. Conclusions: Keratometry measurement with Nidek ARK-510A was not significantly different from Pentacam and Lenstar, and this device can be used in screening programs in emmetropes


Objetivo: Determinar la concordancia y validez de las mediciones queratométricas en niños con el autorefractoqueratómetro Nidek ARK-510A, comparadas con las imágenes de Scheimpflug con Pentacam y el biómetro Lenstar LS 900. Métodos: Este estudio se realizó en 5.620 niños, de edades comprendidas entre 6 y 12 años, en Shahroud, Irán. Se compararon los valores queratométricos mínimo y máximo y la magnitud del astigmatismo corneal mediante cálculo de diferencia pareada, coeficiente de correlación inter-clase, y límites de comcordancia del 95% (LoA) entre dispositivos. Resultados: Tras aplicar los criterios de exclusión, se incluyeron 4.215 ojos derechos en el estudio. Los valores de queratometría mínima media con Nidek ARK-510A, Pentacam y Lenstar fueron de 43,13 ± 1,51, 43,14 ± 1,48, y 42,87 ± 1,46 dioptrías (D), respectivamente, siendo los valores de queratometría máxima media de 43,97 ± 1,59, 44 ± 1,56, y 43,75 ± 1,54 D, respectivamente. Nidek ARK-510A sobre-estimó la queratometría mínima y máxima en 0,25 ± 0,37 y 0,22 ± 0,41, respectivamente, en comparación con Penatcam. El LoA entre Nidek ARK-510A y Pentacam para las mediciones de queratometría mínima y máxima fue de -0,98 a 0,47 D y -1,02 a 0,57 D, respectivamente. El LoA entre Nidek ARK-510A y Lenstar para las mediciones de queratometría mínima y máxima fue de -0,7 a 0,72 D y -0,79 a 0,85 D, respectivamente. El acuerdo entre dispositivos fue mejor en emétropes, y peor en hipermétropes. Para los componentes del vector astigmático, los acuerdos entre dispositivos fueron débiles, aunque existió una mejor concordancia entre Nidek ARK-510A y Pentacam. Conclusiones: La medición de la queratometría realizada con Nidek ARK-510A no fue significativamente diferente a la realizada con Pentacam y Lenstar, pudiendo utilizarse este dispositivo en los programas de chequeo en emétropes


Assuntos
Humanos , Masculino , Feminino , Criança , Refratometria/métodos , Erros de Refração/diagnóstico , Astigmatismo/diagnóstico , Emetropia/fisiologia , Refratometria/instrumentação , Valores de Referência , Biometria/métodos , Estudos Transversais
9.
Appl Opt ; 58(12): 3187-3192, 2019 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-31044793

RESUMO

A bilayer asymmetric photonic crystal slab made of porous Si3N4/SiO2 is designed as a biosensor by considering the optical performance of this photonic crystal slab with a square lattice based on rigorous coupled-wave analysis theory and wavelength interrogation methods. The results show that this bilayer asymmetric photonic crystal can be used as a biosensor according to its excellent linearity relationship between the guided resonance peak shift and refractive index of aqueous solution with or without glycerol. The theoretical sensitivity value of the bilayer asymmetric photonic crystal biosensor is achieved as (S>286 nm/RIU) in the wavelength range from 1400 nm to 1600 nm. These results also indicate that the asymmetry bilayer structure has an important influence on its optical characteristic and sensitivity of the bilayer photonic crystal biosensor, and hence, it can be modified by changing the lattice constant and slab thickness. This research paper is very useful for understanding the application and design of biosensors based on porous structures.


Assuntos
Técnicas Biossensoriais/instrumentação , Compostos de Silício/química , Dióxido de Silício/química , Cristalização , Fótons , Refratometria/instrumentação , Espalhamento de Radiação
10.
J Optom ; 12(2): 99-110, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30879970

RESUMO

PURPOSE: To determine the agreement and validity of keratometric measurements in children with the Nidek ARK-510A auto-refractokeratometer compared to rotating Scheimpflug imaging with Pentacam and biograph with Lenstar LS 900. METHODS: This study was conducted on 5620 schoolchildren aged 6-12 years in Shahroud, Iran. Minimum and maximum keratometry values and corneal astigmatism magnitude were compared by calculation of Paired difference, interclass correlation coefficient, and 95% limits of agreement (LoA) between devices. RESULTS: After applying the exclusion criteria, 4215 right eyes were enrolled into the study. Mean minimum keratometry with Nidek ARK-510A, Pentacam, and Lenstar was 43.13±1.51, 43.14±1.48, and 42.87±1.46 diopters (D), respectively, and mean maximum keratometry was 43.97±1.59, 44.00±1.56, and 43.75±1.54D, respectively. Nidek ARK-510A overestimated minimum and maximum keratometry by 0.25±0.37 and 0.22±0.41, respectively, compared to Penatcam. The LoA between Nidek ARK-510A and Pentacam for minimum and maximum keratometry measurements were -0.98 to 0.47D and -1.02 to 0.57D, respectively. The LoA between Nidek ARK-510A and Lenstar for minimum and maximum keratometry measurements were -0.70 to 0.72D and -0.79 to 0.85D, respectively. The agreement between devices was best in emmetropes, worst in hyperopes. For astigmatic vector components, the agreements between devices were poor but best agreement was between Nidek ARK-510A and Pentacam. CONCLUSIONS: Keratometry measurement with Nidek ARK-510A was not significantly different from Pentacam and Lenstar, and this device can be used in screening programs in emmetropes.


Assuntos
Astigmatismo/diagnóstico , Biometria/instrumentação , Córnea , Doenças da Córnea/diagnóstico , Topografia da Córnea/instrumentação , Técnicas de Diagnóstico Oftalmológico/instrumentação , Refratometria/instrumentação , Criança , Córnea/patologia , Córnea/fisiopatologia , Feminino , Humanos , Masculino , Imagem Óptica/instrumentação , Fotografação/instrumentação , Estudos Prospectivos , Reprodutibilidade dos Testes
11.
Biosens Bioelectron ; 132: 368-374, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30901726

RESUMO

A simple, convenient, and inexpensive method to fabricate optical fiber based biosensors which utilize periodic hole arrays in gold films for signal transduction is reported. The process of hole array formation mainly relies on self-assembly of hydrogel microgels in combination with chemical gold film deposition and subsequent transfer of the perforated film onto an optical fiber tip. In the fabrication process solely chemical wet lab techniques are used, avoiding cost-intensive instrumentation or clean room facilities. The presented method for preparing fiber optic plasmonic sensors provides high throughput and is perfectly suited for commercialization using batch processing. The transfer of the perforated gold film onto an optical fiber tip does not affect the sensitivity of the biosensor ((420 ±â€¯83) nm/refractive index unit (RIU)), which is comparable to sensitivities of sensor platforms based on periodic hole arrays in gold films prepared by significantly more complex methods. Furthermore, real-time and in-line immunoassay studies with a specially designed 3D printed flow cell are presented exploiting the presented optical fiber based biosensors.


Assuntos
Tecnologia de Fibra Óptica/instrumentação , Imunoensaio/instrumentação , Imunoglobulina G/análise , Ressonância de Plasmônio de Superfície/instrumentação , Animais , Desenho de Equipamento , Cabras , Ouro/química , Fibras Ópticas , Impressão Tridimensional , Coelhos , Refratometria/instrumentação
12.
J. optom. (Internet) ; 12(1): 22-29, ene.-mar. 2019. grab, tab
Artigo em Inglês | IBECS | ID: ibc-178509

RESUMO

Background: Accommodation is often recorded at a low sampling rate using devices such as autorefractors that are designed to measure the static refractive error. It is therefore important to determine if that resolution is sufficient to accurately measure the dynamic properties of accommodation. The current study provides both theoretical and empirical evidence on the ideal sampling rate necessary to measure a dynamic response. Methods: Accommodative and disaccommodative step stimuli ranging from 1-3 D (1 D steps) were presented using a Badal optical system. Responses from 12 children (8-13 years) and 6 adults (20-35 years) were recorded using a dynamic photorefractor (DPR). Fast Fourier transformation was applied to the unsmoothed dynamic responses including position, velocity and acceleration. Also, velocity and acceleration main sequence (MS) characteristics were compared between three photorefractor conditions on 3 subjects. Results: The Nyquist sampling limit necessary to accurately estimate position, velocity and acceleration was at least 5, 10 and 70 Hz, respectively. Peak velocity and acceleration were significantly underestimated at a lower rate (p < 0.5). However, the slope of MS remained invariant with sampling rate (p > 0.5). Conclusion: Contrary to the previous findings, a dynamic accommodative response exhibited frequencies larger than 10Hz. Stimulus direction and amplitude had no influence on the frequencies present in the dynamic response. Peak velocity and acceleration can be significantly underestimated when sampled at a lower rate. Taken as a whole, low sampling rate instruments can accurately estimate static accommodation, however, caution needs to be exercised when using them for dynamic accommodation


La acomodación se registra a menudo a una tasa de muestreo baja, utilizando dispositivos tales como los autorrefractómetros que están diseñados para medir el error refractivo estático. Por tanto, es importante determinar si dicha resolución es suficiente para medir con precisión las propiedades dinámicas de la acomodación. El estudio actual aporta evidencia tanto teórica como empírica acerca de la tasa de muestreo necesaria para medir una respuesta dinámica. Métodos: Se presentaron estímulos de alteraciones de estimulación y relajación (desacomodación) de la acomodación que oscilaron entre 1 y 3 D (pasos de 1 D) utilizando un sistema óptico Badal. Se registraron las respuestas de 12 niños (de 8 a 13 años) y 6 adultos (de 20 a 35 años) utilizando un sistema de fotorrefracción dinámico (DPR). La transformación rápida de Fourier se aplicó a las respuestas dinámicas no uniformes incluyendo posición, velocidad y aceleración. También se compararon las características de la secuencia principal de velocidad y aceleración entre las tres situaciones del sistema de fotorrefracción en 3 sujetos. Resultados: El límite de muestreo de Nyquist necesario para calcular con precisión la posición, velocidad y aceleración fue de al menos 5, 10 y 70Hz respectivamente. La velocidad y aceleración máximas se subestimaron significativamente a una tasa inferior (p < 0,5). Sin embargo, la pendiente de la secuencia principal permaneció invariable con la tasa de muestreo (p > 0,5). Conclusión: Contrariamente a los hallazgos anteriores, la respuesta acomodativa dinámica mostró unas frecuencias superiores a 10Hz. La dirección y amplitud del estímulo no influyeron en las frecuencias presentes en la respuesta dinámica. La velocidad y aceleración máximas pueden subestimarse significativamente cuando se muestrean a una tasa menor. En conjunto, los instrumentos de baja tasa de muestreo pueden calcular con precisión la acomodación estática; sin embargo, debe actuarse con precaución a la hora de calcular la acomodación dinámica


Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Adulto Jovem , Adulto , Acomodação Ocular/fisiologia , Optometria/métodos , Refratometria/métodos , Análise de Fourier , Optometria/instrumentação , Refração Ocular/fisiologia , Refratometria/instrumentação
13.
J Optom ; 12(1): 22-29, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-29580938

RESUMO

BACKGROUND: Accommodation is often recorded at a low sampling rate using devices such as autorefractors that are designed to measure the static refractive error. It is therefore important to determine if that resolution is sufficient to accurately measure the dynamic properties of accommodation. The current study provides both theoretical and empirical evidence on the ideal sampling rate necessary to measure a dynamic response. METHODS: Accommodative and disaccommodative step stimuli ranging from 1-3D (1D steps) were presented using a Badal optical system. Responses from 12 children (8-13 years) and 6 adults (20-35 years) were recorded using a dynamic photorefractor (DPR). Fast Fourier transformation was applied to the unsmoothed dynamic responses including position, velocity and acceleration. Also, velocity and acceleration main sequence (MS) characteristics were compared between three photorefractor conditions on 3 subjects. RESULTS: The Nyquist sampling limit necessary to accurately estimate position, velocity and acceleration was at least 5, 10 and 70Hz, respectively. Peak velocity and acceleration were significantly underestimated at a lower rate (p<0.5). However, the slope of MS remained invariant with sampling rate (p>0.5). CONCLUSION: Contrary to the previous findings, a dynamic accommodative response exhibited frequencies larger than 10Hz. Stimulus direction and amplitude had no influence on the frequencies present in the dynamic response. Peak velocity and acceleration can be significantly underestimated when sampled at a lower rate. Taken as a whole, low sampling rate instruments can accurately estimate static accommodation, however, caution needs to be exercised when using them for dynamic accommodation.


Assuntos
Acomodação Ocular/fisiologia , Optometria/métodos , Refratometria/métodos , Adolescente , Adulto , Criança , Feminino , Análise de Fourier , Humanos , Masculino , Optometria/instrumentação , Refração Ocular/fisiologia , Refratometria/instrumentação , Adulto Jovem
14.
Lab Chip ; 19(3): 464-474, 2019 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-30570636

RESUMO

On-chip high-throughput phenotyping of single cells has gained a lot of interest recently due to the discrimination capability of label-free biomarkers such as whole-cell deformability and refractive index. Here we present on-chip refractive index cytometry (RIC) for whole-cell deformability at a high measurement rate. We have further exploited a previously published on-chip optical characterization method which enhances cellular discrimination through the refractive index measurement of single cells. The proposed on-chip RIC can simultaneously probe the cellular refractive index, effective volume and whole-cell deformability while reaching a measurement rate up to 5000 cells per second. Additionally, the relative position of the nucleus inside the cell is reflected by the asymmetry of the measured curve. This particular finding is confirmed by our numerical simulation model and emphasized by a modified cytoskeleton HL-60 cells model. Furthermore, the proposed device discriminated HL-60 derived myeloid cells such as neutrophils, basophils and promyelocytes, which are indistinguishable using flow cytometry. To our knowledge, this is the first integrated device to simultaneously characterize the cellular refractive index and whole-cell deformability, yielding enhanced discrimination of large myeloid cell populations.


Assuntos
Citometria de Fluxo/instrumentação , Dispositivos Lab-On-A-Chip , Fenômenos Mecânicos , Refratometria/instrumentação , Análise de Célula Única/instrumentação , Fenômenos Biomecânicos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Citocalasina B/farmacologia , Células HL-60 , Humanos , Fenômenos Mecânicos/efeitos dos fármacos
15.
J Dairy Sci ; 102(1): 557-566, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30471908

RESUMO

The objective of this study was to evaluate a filter system to harvest plasma to assess failure of passive transfer (FPT) in newborn calves. Blood samples (n = 227) for serum and plasma harvesting were collected via jugular vein puncture from Holstein calves aged 1 to 7 d from 4 commercial dairy herds in Northeast Germany. Serum IgG concentrations were determined using a sandwich ELISA. Failure of passive transfer was defined as IgG concentrations <10 mg/mL and used as a gold standard. One handheld optical refractometer (Euromex Holland, Arnhem, the Netherlands) and 2 digital Brix refractometers (device 1: HI 96801 digital refractometer, Hanna Instruments, Woonsocket, RI; device 2: Misco PA201, Misco, Solon, OH) were used to analyze total proteins in serum or plasma. The colostrum uptake of the calf can thus be monitored and calves with FPT can be identified. Serum was obtained through centrifugation. Plasma was obtained through either a filter system or centrifugation. For plasma filtration, approximately 2 mL of lithium heparin blood was injected into the inlet reservoir of a plasma filter (2-Drop-Filter, Pharmadoc, Lübeck, Germany) using a disposable syringe. Receiver operating characteristic curve analyses were used to determine optimum thresholds for each of the 3 devices using different media. Sixty-seven (30%) calves had FPT. For the handheld optical refractometer, the optimum threshold was 5.6 g/dL [sensitivity 70.1%; specificity 80.0%; positive predictive value (PPV) 60.1%; negative predictive value (NPV) 86.2%; area under the curve (AUC) 0.85] using serum. For centrifuged plasma, the optimum threshold was 6.3 g/dL (sensitivity 82.1%; specificity 68.1%; PPV 52.5%; NPV 89.9%; AUC 0.84), and for filtered plasma, the threshold was 6.0 g/dL (sensitivity 56.7%; specificity 90.0%; PPV 70.9%; NPV 82.9%; AUC 0.80). For device 1, the optimum threshold was 8.9% Brix (sensitivity 82.1%; specificity 63.8%; PPV 48.7%; NPV 89.5%; AUC 0.81), 9.4% Brix (sensitivity 76.1%; specificity 73.7%; PPV 55.4%; NPV 87.8%; AUC 0.80), using serum and centrifuged plasma, respectively. For device 2, the optimum threshold was 8.7% Brix (sensitivity 74.6%; specificity 76.2%; PPV 57.4%; NPV 87.5%; AUC 0.83), 9.5% Brix (sensitivity 80.6%; specificity 70.6%; PPV 54.0%; NPV 89.5%; AUC 0.83), and 9.2% Brix (sensitivity 58.2%; specificity 87.5%; PPV 66.6%; NPV 83.0%; AUC 0.80) using serum, centrifuged plasma, and filtered plasma, respectively. Based on the AUC, the 3 devices yielded comparable test characteristics to identify calves with FPT. In conclusion, a filter system can be used to facilitate the evaluation of FPT as a point of care technique in calves without the need for serum centrifugation.


Assuntos
Animais Recém-Nascidos/imunologia , Bovinos/imunologia , Colostro/imunologia , Filtração/veterinária , Imunidade Materno-Adquirida/imunologia , Imunoglobulina G/sangue , Animais , Proteínas Sanguíneas/análise , Centrifugação/veterinária , Feminino , Filtração/métodos , Alemanha , Plasmaferese/veterinária , Gravidez , Curva ROC , Refratometria/instrumentação , Refratometria/veterinária , Sensibilidade e Especificidade
16.
ACS Nano ; 12(12): 11892-11898, 2018 12 26.
Artigo em Inglês | MEDLINE | ID: mdl-30475589

RESUMO

Refractometry, namely, the measurement of refractive index (RI), provides information about various sample properties such as concentrations and molecular structure. One physical phenomenon which enables precise determination of a sample's RI in a microscope is the supercritical-angle fluorescence. This effect is observed when the fluorescence from an emitter near a glass-medium interface is captured by an objective lens with a high numerical aperture. The materials' index mismatch creates a distinguishable transition in the intensity pattern at the back focal plane of the objective that changes proportionally to the RI of the media. Here, we present a refractometry approach in which the fluorophores are preattached to the bottom surface of a microfluidic channel, enabling highly sensitive determination of the RI using tiny amounts of liquid (picoliters). With this method, we attained a standard deviation of 3.1 × 10-5 and a repeatability of 2.7 × 10-5 RI units. We first determine the capabilities of the device for glycerol-water solutions and then demonstrate the relevance of our system for monitoring changes in biological systems. As a model system, we show that we can detect single bacteria ( Escherichia coli) and measure population growth.


Assuntos
Microscopia de Fluorescência/instrumentação , Refratometria/instrumentação , Técnicas Biossensoriais , Escherichia coli/citologia , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/isolamento & purificação , Glicerol/química , Dispositivos Lab-On-A-Chip , Modelos Teóricos , Propriedades de Superfície , Água/química
17.
ACS Sens ; 3(11): 2223-2231, 2018 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-30380852

RESUMO

Aqueous solutions of alcohols are used in several applications, from pharmaceutics and biology, to chemical, biofuel, and food industries. Nonetheless, development of a simple, inexpensive, and portable sensing device for the quantification of water in water-ethanol mixtures remains a significant challenge. Photonic crystals (PhCs) operating at very high-order photonic bandgaps (PBGs) offer remarkable opportunities for the realization of chemical sensors with high sensitivity and low detection limit. However, high-order PhC structures have been mostly confined to mere theoretical speculations so far, their effective realization requiring microfabrication tools enabling the control of periodic refractive index modulations at the submicrometric scale with extremely high accuracy and precision. Here, we report both experimental and theoretical results on high-sensitivity chemical analysis using vertical, silicon/air 1D-PhCs with spatial period of 10 and 20 µm (namely, over 10 times the operation wavelength) featuring ultra-high-order PBGs in the near-infrared region (namely, up to 50th at 1.1 µm). Fabrication of high-order 1D-PhCs was carried out by electrochemical micromachining (ECM) of silicon, which allowed both surface roughness and deviation from vertical of etched structures to be controlled below 5 nm and 0.1%, respectively. Optical characterization of ECM-fabricated 1D-PhCs, which was performed by acquiring reflectivity spectra over the wavelength range 1-1.7 µm, highlighted the presence of ultra-high-order PBGs with minor optical losses (i.e., <1 dB in reflectivity) separated by deep reflectivity notches with high Q-factors (i.e., >6000), in good agreement with theoretical calculations. Remarkably, the use of high-order 1D-PhCs as refractometric transducers for the quantitative detection of traces of water in water-ethanol mixtures, allowed high sensitivity (namely, either 1000 nm/RIU or ∼0.4 nm/% of water), good detection limit (namely, 5 × 10-3 RIU or ∼10% water), and excellent resolution (namely, either 6 × 10-4 RIU or 1.6% of water) to be reliably achieved on a detection volume of about 168 fL.


Assuntos
Etanol/química , Silício/química , Água/análise , Calibragem , Luz , Limite de Detecção , Microtecnologia , Refratometria/instrumentação , Refratometria/métodos , Silício/efeitos da radiação , Transdutores , Água/química
18.
J Vis Exp ; (140)2018 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-30417865

RESUMO

In recent years, a push for developing novel silicon photonic devices for telecommunications has generated a vast knowledge base that is now being leveraged for developing sophisticated photonic sensors. Silicon photonic sensors seek to exploit the strong confinement of light in nano-waveguides to transduce changes in physical state to changes in resonance frequency. In the case of thermometry, the thermo-optic coefficient, i.e., changes in refractive index due to temperature, causes the resonant frequency of the photonic device such as a Bragg grating to drift with temperature. We are developing a suite of photonic devices that leverage recent advances in telecom compatible light sources to fabricate cost-effective photonic temperature sensors, which can be deployed in a wide variety of settings ranging from controlled laboratory conditions, to the noisy environment of a factory floor or a residence. In this manuscript, we detail our protocol for the fabrication and testing of photonic thermometers.


Assuntos
Fótons/uso terapêutico , Refratometria/instrumentação , Silício/química , Termômetros/normas
19.
Lab Chip ; 18(22): 3484-3491, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30303499

RESUMO

Optical diffraction tomography (ODT) enables the reconstruction of the three-dimensional (3D) refractive-index (RI) distribution of a biological cell, which provides invaluable information for cellular and subcellular structures in a non-invasive manner. However, ODT suffers from an inferior axial resolution, due to the limited accessible angles imposed by the numerical aperture of the objective lens. In this study, we propose and experimentally demonstrate an approach to enhance the 3D reconstruction performance in ODT. By employing trapezoidal micromirrors, side scattered signals from the sample are measured for various side plane-wave-illumination angles. By combining the side scattered fields with the forward scattered fields, the axial resolution and 3D image quality of ODT are improved, without changing optical instruments. The feasibility and applicability of the proposed method are demonstrated by reconstructing the 3D RI distribution of a red blood cell and HeLa cells in hydrogel. We also present systematic analyses of the improved 3D imaging performance using numerical simulations and experimental measurements for the 3D transfer function, a point object, and a microsphere. The analyses demonstrate an improved axial resolution of 0.31 µm, 4.8 times smaller than that of the conventional method. The proposed method enables the non-invasive and accurate 3D imaging of 3D cultured cells, which is crucial for cell biology studies.


Assuntos
Imageamento Tridimensional/instrumentação , Fenômenos Ópticos , Refratometria/instrumentação , Tomografia/instrumentação , Eritrócitos/citologia , Células HeLa , Humanos
20.
J Vis Exp ; (139)2018 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-30247465

RESUMO

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.


Assuntos
Dispositivos Lab-On-A-Chip , Refratometria/instrumentação , Células Cultivadas , Dimetilpolisiloxanos/química , Desenho de Equipamento
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