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Serum total protein (STP) refractometry is a widely used indicator of failed transfer of passive immunity (FTPI), defined as serum IgG concentrations of <10 mg/mL or STP levels <5.2 g/dL measured at 24 h of life. However, recent reports have demonstrated that refractometry could be inaccurate at estimating serum IgG concentrations and FTPI when calves are fed colostrum replacer (CR). The objective of this study was to evaluate the accuracy of STP measurements to estimate FTPI in calves fed CR compared with calves fed maternal colostrum. Blood was collected from dairy calves fed maternal colostrum (n = 927) or colostrum-derived CR (n = 1,258) and analyzed for STP and serum IgG. Serum total protein was measured with a digital refractometer, whereas radial immunodiffusion was used to determine IgG concentrations. Calves fed maternal colostrum had a mean STP of 5.80 ± 0.72 (standard deviation) g/dL and a mean IgG concentration of 22.81 ± 10.14 mg/mL, respectively, whereas calves fed CR had a mean STP and IgG concentration of 5.14 ± 0.50 g/dL and 12.78 ± 4.60 mg/mL, respectively. Rates of FTPI for calves fed maternal colostrum or CR were 4.2% and 27.26%, respectively. Calves were considered to have FTPI if their IgG postcolostrum feeding was <10 mg/mL. Logistic and linear regression analyses were performed to determine cutoff points and existent relationships between STP and IgG. Serum total protein and IgG for calves fed maternal colostrum were highly correlated. In contrast, STP and IgG for calves fed CR were lowly correlated. A receiver operator characteristic curve analysis demonstrated that an STP cutoff point that could predict FTPI when calves are fed CR would be 4.9 g/dL (sensitivity = 0.68; specificity = 0.75). This study suggests that current cutoff points used for STP inflates the number of calves estimated to have FTPI when they are fed CR., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Purpose: To conduct a clinical validation of a virtual reality-based experimental system that is able to assess the spherical subjective refraction simplifying the methodology of ocular refraction., Methods: For the agreement assessment, spherical refraction measurements were obtained from 104 eyes of 52 subjects using three different methods: subjectively with the experimental prototype (Subj.E) and the classical subjective refraction (Subj.C); and objectively with the WAM-5500 autorefractor (WAM). To evaluate precision (intra- and inter-observer variability) of each refractive tool independently, 26 eyes were measured in four occasions., Results: With regard to agreement, the mean difference (±SD) for the spherical equivalent (M) between the new experimental subjective method (Subj.E) and the classical subjective refraction (Subj.C) was -0.034D (±0.454D). The corresponding 95% Limits of Agreement (LoA) were (-0.856D, 0.924D). In relation to precision, intra-observer mean difference for the M component was 0.034±0.195D for the Subj.C, 0.015±0.177D for the WAM and 0.072±0.197D for the Subj.E. Inter-observer variability showed worse precision values, although still clinically valid (below 0.25D) in all instruments., Conclusions: The spherical equivalent obtained with the new experimental system was precise and in good agreement with the classical subjective routine. The algorithm implemented in this new system and its optical configuration has been shown to be a first valid step for spherical error correction in a semiautomated way., (Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Objective: To compare total protein (TP) concentrations in canine pleural and abdominal fluid specimens as measured by refractometry and biuret assay., Design: Diagnostic test evaluation., Sample: Data regarding 92 pleural and 148 abdominal fluid specimens from dogs with various diseases., Procedures: TP concentrations in fluid specimens as measured by refractometry and biuret assay were recorded. Strength of association between sets of measurements was assessed by Spearman rank correlations and Bland-Altman plots. Optimal concentration cutoff for diagnostic discrimination between exudate and nonexudate was identified by construction of receiver operating characteristic curves., Results: Median TP concentration in pleural fluid specimens was 2.7 g/dL (range, 0.3 to 4.8 g/dL) for refractometry and 2.9 g/dL (range, 0.7 to 5.8 g/dL) for biuret assay. Median TP concentration in abdominal fluid specimens was 3.5 g/dL (range, 0.1 to 6.0 g/dL) for refractometry and 3.5 g/dL (range, 0.6 to 5.7 g/dL) for biuret assay. Correlation was significant between refractometric and biuret results for pleural (ρ = 0.921) and abdominal (ρ = 0.908) fluid. Bland-Altman plots revealed bias of -0.18 g/dL for pleural fluid and -0.03 g/dL for abdominal fluid for refractometry versus biuret assay. With a TP concentration of ≥ 3 g/dL used to distinguish exudate from nonexudate, sensitivity of refractometry was 77% for pleural fluid and 80% for abdominal fluid. Specificity was 100% and 94%, respectively., Conclusions and Clinical Relevance: Refractometry yielded acceptable results for measurement of TP concentration in canine pleural and abdominal fluid specimens, providing a more rapid and convenient method than biuret assay.

Context: Urine specific gravity (Usg), measured by a handheld manual refractometer (MAN), has been recognized as a valid and practical means of assessing hydration status. Newer, digital refractometers are faster and more user friendly but have not been validated against the traditional MAN., Objective: To compare the reliability and validity of 2 digital refractometer models and a MAN., Design: Descriptive laboratory study., Setting: Research laboratory., Patients or Other Participants: Sample of convenience was recruited from the local university and surrounding community (n = 82)., Intervention(s): Participants provided multiple urine samples (n = 124) over a 5-month period under various hydration conditions., Main Outcome Measure(s): Urine specific gravity was compared among a MAN, a digital refractometer requiring the prism to be dipped (DIP) into a urine sample, and a digital refractometer that requires urine to be pipetted (PIP) onto its prism for analysis., Results: The MAN measurements were strongly correlated with the DIP (r = 0.99, P < .001) and PIP (r = 0.97, P < .001) measurements. Bland-Altman analyses revealed slight mean underestimation (95% upper and lower levels of agreement) between MAN and DIP (-0.0012 [0.0028] and PIP -0.0011 [0.0035], respectively) and trends toward increased underestimation at higher Usg. Measurement error ≥ .005 was greater for PIP (4/124, 3.2%) than for DIP (2/124, 1.6%)., Conclusions: Negligible differences were exhibited between PIP and DIP, with both displaying acceptable reliability and validity compared with the MAN. However, the Bland-Altman analysis suggests underestimation bias for the DIP and PIP as Usg increases, with the potential for rare but substantial underestimation when using PIP that should be recognized by clinicians, particularly when used as a screening measure in weight-class sports.

Three dimensional shape measurement in the microscopic range becomes increasingly important with the development of micro manufacturing technology. Microscopic fringe projection techniques offer a fast, robust, and full-field measurement for field sizes from approximately 1 mm 2 to several cm 2 . However, the depth of field is very small due to the imaging of non-telecentric microscope, which is often not sufficient to measure the complete depth of a 3D-object. And the calibration of phase-to-depth conversion is complicated which need a precision translation stage and a reference plane. In this paper, we propose a novel telecentric phase-shifting projected fringe profilometry for small and thick objects. Telecentric imaging extends the depth of field approximately to millimeter order, which is much larger than that of microscopy. To avoid the complicated phase-to-depth conversion in microscopic fringe projection, we develop a new system calibration method of camera and projector based on telecentric imaging model. Based on these, a 3D reconstruction of telecentric imaging is presented with stereovision aided by fringe phase maps. Experiments demonstrated the feasibility and high measurement accuracy of the proposed system for thick object.

We report on a tunable continuous-wave mid-infrared optical parametric oscillator (OPO), which is locked to a fully stabilized near-infrared optical frequency comb using a frequency doubling scheme. The OPO is used for 40 GHz mode-hop-free, frequency-comb-locked scans in the wavelength region between 2.7 and 3.4 μm. We demonstrate the applicability of the method to high-precision cavity-ring-down spectroscopy of nitrous oxide (N 2 O) and water (H 2 O) at 2.85 µm and of methane (CH 4 ) at 3.2 μm.

For structured light system calibration, one popular approach is to treat the projector as an inverse camera. This is usually performed by projecting horizontal and vertical sequences of patterns to establish one-to-one mapping between camera points and projector points. However, for a well-designed system, either horizontal or vertical fringe images are not sensitive to depth variation and thus yield inaccurate mapping. As a result, the calibration accuracy is jeopardized if a conventional calibration method is used. To address this limitation, this paper proposes a novel calibration method based on optimal fringe angle determination. Experiments demonstrate that our calibration approach can increase the measurement accuracy up to 38% compared to the conventional calibration method with a calibration volume of 300(H)  mm×250(W)  mm×500(D)  mm.

Navigation plays a vital role in our daily life. As traditional and commonly used navigation technologies, Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS) can provide accurate location information, but suffer from the accumulative error of inertial sensors and cannot be used in a satellite denied environment. The remarkable navigation ability of animals shows that the pattern of the polarization sky can be used for navigation. A bio-inspired POLarization Navigation Sensor (POLNS) is constructed to detect the polarization of skylight. Contrary to the previous approach, we utilize all the outputs of POLNS to compute input polarization angle, based on Least Squares, which provides optimal angle estimation. In addition, a new sensor calibration algorithm is presented, in which the installation angle errors and sensor biases are taken into consideration. Derivation and implementation of our calibration algorithm are discussed in detail. To evaluate the performance of our algorithms, simulation and real data test are done to compare our algorithms with several exiting algorithms. Comparison results indicate that our algorithms are superior to the others and are more feasible and effective in practice.

We address calibration of Mueller polarimeters in the presence of noise. We compare an extension of the eigenvalue calibration method (ECM) and a maximum likelihood (ML) method. The performances of these two calibration methods are investigated with numerical simulations and real experiments on a broadband infrared polarimeter. It is found that the ML method is superior to the extended ECM in terms of calibration precision and can be used at lower signal-to-noise ratio.

We present a concept of suppression of the influence of variations of the refractive index of air in displacement measuring interferometry. The principle is based on referencing of wavelength of the coherent laser source in atmospheric conditions instead of traditional stabilization of the optical frequency and indirect evaluation of the refractive index of air. The key advantage is in identical beam paths of the position measuring interferometers and the interferometer used for the wavelength stabilization. Design of the optical arrangement presented here to verify the concept is suitable for real interferometric position sensing in technical practice especially where a high resolution measurement within some limited range in atmospheric conditions is needed, e.g. in nanometrology.

The spatial resolution of OFDR is normally degraded by the laser phase noise, deviations from linear frequency scan and acoustic noise in the fibers. A method for mitigating these degradation mechanisms, without using an auxiliary interferometer, via inline auxiliary points, is presented and demonstrated experimentally. Auxiliary points are points that are a priori known to have (spatial) impulse reflectivities. Their responses are used for compensating the phase deviations that degrade the response of points that are further away from the source.

Mueller matrix differential decomposition is a novel method for retrieving the polarimetric properties of general depolarizing anisotropic media [N. Ortega-Quijano and J. L. Arce-Diego, Opt. Lett. 36, 1942 (2011), R. Ossikovski, Opt. Lett. 36, 2330 (2011)]. The method has been verified for Mueller matrices available in the literature. We experimentally validate the decomposition for five different experimental setups with different commutation properties and controlled optical parameters, comparing the differential decomposition with the forward and reverse polar decompositions. The results enable to verify the method and to highlight its advantages for certain experimental applications of high interest.

We show that the volumetric field distribution in the focal region of a high numerical aperture focusing system can be efficiently calculated with a three-dimensional Fourier transform. In addition to focusing in a single medium, the method is able to calculate the more complex case of focusing through a planar interface between two media of mismatched refractive indices. The use of the chirp z-transform in our numerical implementation of the method allows us to perform fast calculations of the three-dimensional focused field distribution with good accuracy.

We propose a novel way to achieve an exceptionally wide frequency range where metamaterial possesses negative effective permeability. This can be achieved by employing a nonlinear response of metamaterials. We demonstrate that, with an appropriate design, a frequency band exceeding 100% is available for a range of signal amplitudes. Our proposal provides a significant improvement over the linear approach, opening a road towards broadband negative refraction and its applications.

The pyramid sensor (PS) is an interesting alternative to the Shack-Hartmann wavefront sensor (SH WFS) for astronomical Adaptive Optics (AO) because of its potential advantages in sensitivity and applicability to novel wavefront sensing schemes. The PS uses a pyramidal prism to perform a knife-edge test in two dimensions simultaneously and relies on modulating the position of the prism to increase the linear dynamic range. It has been suggested that this could also be accomplished by a static diffusing element. We test this idea and show that the diffuser produces a modulation effect. We compare the results of our PS to a SH WFS measuring spatial and temporal properties of real turbulence produced in the lab with a hot-air turbulence generator.

Traditional methods for geometrical camera calibration are based on calibration grids or single pixel illumination by collimated light. A new method for geometrical sensor calibration by means of diffractive optical elements (DOE) in connection with a laser beam equipment is presented. This method can be especially used for 2D-sensor array systems but in principle also for line scanners., ((c) 2008 Optical Society of America)

We present studies of polarized absorption [linear dichroism (LD)] and fluorescence polarization of the styryl derivative (LDS 798) embedded in oriented poly(vinyl alcohol) (PVA) films. These films were oriented by progressive stretching up to eight folds. Both vertical and horizontal components of absorptions and fluorescence were measured and dichroic ratios were determined for different film stretching ratios. The dichroic ratio and fluorescence anisotropy values were analyzed as a function of PVA film stretching ratio by fitting according to the previously developed theory. For maximum stretching ratios, exceptionally high anisotropy (approximately 0.8) and polarization (approximately 0.9) values have been measured. The stretched films have high polarization values also for isotropic excitation in a wide spectral range (500-700 nm). Such films can be conveniently used as high polarization standards and we envision they will also have applications in near infrared (NIR) imaging microscopy, where they can be used for correcting an instrumental factor in polarization measurements.

A truly endless polarization stabilization experiment with a tracking speed of 15 krad/s is presented. The high-speed polarization tracking is realized by using calibrated lithium niobate linear retardation waveplates as the polarization transformers combined with a very fast digital controller running on a field-programmable gate array (FPGA).

The calibration of a complete Stokes birefringent prismatic imaging polarimeter (BPIP) in the MWIR is demonstrated. The BPIP technique, originally developed by K. Oka, is implemented with a set of four Yttrium Vanadate (YVO(4)) crystal prisms. A mathematical model for the polarimeter is presented in which diattenuation due to Fresnel effects and dichroism in the crystal are included. An improved polarimetric calibration technique is introduced to remove the diattenuation effects, along with the relative radiometric calibration required for the BPIP operating with a thermal background and large detector offsets. Data demonstrating emission polarization are presented from various blackbodies, which are compared to data from our Fourier transform infrared spectropolarimeter.

Objective: To determine sensitivity and specificity of 4 methods to assess colostral IgG concentration in dairy cows and determine the optimal cutpoint for each method., Design: Cross-sectional study., Animals: 160 Holstein dairy cows., Procedures: 171 composite colostrum samples collected within 2 hours after parturition were used in the study. Test methods used to estimate colostral IgG concentration consisted of weight of the first milking, 2 hydrometers, and an electronic refractometer. Results of the test methods were compared with colostral IgG concentration determined by means of radial immunodiffusion. For each method, sensitivity and specificity for detecting colostral IgG concentration < 50 g/L were calculated across a range of potential cutpoints, and the optimal cutpoint for each test was selected to maximize sensitivity and specificity., Results: At the optimal cutpoint for each method, sensitivity for weight of the first milking (0.42) was significantly lower than sensitivity for each of the other 3 methods (hydrometer 1, 0.75; hydrometer 2, 0.76; refractometer, 0.75), but no significant differences were identified among the other 3 methods with regard to sensitivity. Specificities at the optimal cutpoint were similar for all 4 methods., Conclusions and Clinical Relevance: Results suggested that use of either hydrometer or the electronic refractometer was an acceptable method of screening colostrum for low IgG concentration; however, the manufacturer-defined scale for both hydrometers overestimated colostral IgG concentration. Use of weight of the first milking as a screening test to identify bovine colostrum with inadequate IgG concentration could not be justified because of the low sensitivity.

Silica nanospheres with diameters ranging from 60 nm to 269 nm are investigated as an alternative to polystyrene spheres for calibrating laser-scattering-based wafer surface inspection systems, since they are less susceptible to changes upon ultraviolet exposure. Polystyrene and silica spheres were classified by differential mobility analysis before being deposited onto bare silicon wafers, and scattered signals were measured by two commercial tools using 488 nm and 355 nm laser light. The instrument signals were modeled by integrating a theoretically-determined differential cross section over the collection geometry of each tool, and the predicted signals were compared to the measured signals. The resulting calibrations, whether performed using the polystyrene spheres, the silica spheres, or both, were found to be equivalent and to meet industry requirements, provided the index of refraction of the silica spheres was allowed to be a floating parameter. The indices were found to be 1.413 and 1.421 at 488 nm and 355 nm, respectively, consistent with a void fraction of 11.4%.

A technique is described for calibrating the amplitude of motion of a phase mask typically used for inscribing fibre Bragg grating (FBG) structures. The motion of the phase mask is detected using a simple Michelson interferometer that can be readily mounted onto an FBG writing system. The output of the interferometer provides a direct indication of the phase mask motion as a function of the true periodicity of the phase mask structure and so is ideally suited to inscription of apodised or phase shifted FBG structures. The technique can be automated and can achieve accuracies of +/-1 nm in approximately 1 minute.

We present a method for calibrating a polarization state analyzer that uses a set of well- characterized reference polarization states and makes no assumptions about the optics contained in the polarimeter other than their linearity. The method requires that a matrix be constructed that contains the data acquired for each of the reference polarization states and that this matrix be pseudoinverted. Since this matrix is usually singular, we improve the method by performing the pseudoinversion by singular value decomposition, keeping only the four largest singular values. We demonstrate the calibration technique using an imaging polarimeter based upon liquid crystal variable retarders and with light emitting diode (LED) illumination centered at 472 nm, 525 nm, and 630 nm. We generate the reference polarization states by using an unpolarized source, a single polarizer, and a Fresnel rhomb. This method is particularly useful when calibrations are performed on field-grade instruments at a centrally maintained facility and when a traceability chain needs to be maintained.

Accurate wavelength assignment of each spectral element for spectral-domain optical coherence tomography (SD-OCT) and optical frequency domain imaging (OFDI) is required for proper construction of biological tissue cross-sectional images. This becomes more critical for functional extensions of these techniques, especially in polarization-sensitive optical coherence tomography (PS-OCT), where incorrect wavelength assignment between the two orthogonal polarization channels leads to polarization artifacts. We present an autocalibration method for wavelength assignment that does not require separate calibration measurements and that can be applied directly on actual data. Removal of the birefringence artifact is demonstrated in a PS-OCT system with picometer accuracy in the relative wavelength assignment, resulting in a residual phase error of 0.25 deg/100 microm. We also demonstrate, for the first time, a quantitative birefringence map of an in vivo human retinal nerve fiber layer.

Monitoring the passive transfer of immunoglobulins from colostrums particularly in noncentrifuged samples can be useful for calf health management programs. The results of total solids refractometry from centrifuge and noncentrifuge harvested sources of serum were highly correlated (R2 = 0.95). Results from a digital and a hand-held refractometer were highly correlated (R2 = 0.96).

The purpose of this paper is to describe the use of LGC Promochem AEA 1001 to AEA 1003 monosized fiber-analog shape standards in the study of the effect of particle shape on laser diffraction (LD) particle size analysis (psa). The psa of the AEA standards was conducted using LD psa systems from Beckman Coulter, Horiba, and Malvern Instruments. Flow speed settings, sample refractive index values, and sample cell types were varied to examine the extent to which the shape effect on LD psa results is modified by these variables. The volume and number probability plots resulting from these measurements were each characterized by a spread in the particle size distribution that roughly extended from the breadth to the longest dimension of the particles. For most of the selected sample refractive index values, the volume probability plots were characterized by apparent bimodal distributions. The results, therefore, provide experimental verification of the conclusions from theoretical studies of LD psa system response to monosized elliptical particles in which this apparent bimodality was the predicted result in the case of flow-oriented particles. The data support the findings from previous studies conducted over the past 10 years that have called into question the verity of the tenets of, and therefore the value of the application of, the equivalent spherical volume diameter theory and the random particle orientation model to the interpretation of LD psa results from measurements made on nonspherical particles.

The concentration of detergent in membrane protein preparations can have a critical role on protein stability, function, and the potential for crystallization. Unfortunately, dialysis or protein concentration can lead to an unknown amount of detergent in the final membrane protein preparations. Here we present a method for the determination of detergent concentration based on refractive index of the detergent solution. This method was applied to quantitate the amount of detergent remaining in solution after concentration in various concentrators. We found that the ability of the tested detergents to pass through the molecular weight cutoff membrane correlates well with detergent micelle size. Therefore, the micelle size can be used as a rough guide to estimate the retention of a given detergent in various molecular weight cutoff concentrators. The refractive index method is exceptionally informative when coupled with size exclusion chromatography and light scattering, and can be used to determine the oligomeric state of the membrane protein, the size of a protein-associated micelle, as well as the amount and size of the unbound detergent micelle.

The objective of this study was to evaluate the quality of the measurement of dog urine dilution/concentration by comparing osmolality with three methods of specific gravity (USG) measurement, i.e. weighing, refractometry and test strips. In unselected urine samples from 182 dogs there was a better agreement between osmolality and USG determination by refractometry (r = 0.92) than by weighing (r = 0.82) or by test strips (r = 0.27). There was an almost linear relationship between osmolality and USG: osmolality (mOsm/kg) = 36646(34318/38974) x (USGref - 1) + 25(-39/88); calculated osmolality differed from measured osmolality by more than 500 mOsm/kg in only 8 of 181 samples. There was a good agreement between USG determination by weighing and refractometry: USGref = 1.000(0.905/1.095) x USGweighing - 0.0004(-0.0019/0.0027), with a moderate bias. Only 12% of the differences between the two methods exceeded 0.010. Test strip assessment of USG was unreliable because of systematic underestimation and should not be used for dog urine. Refractometry is the best technique for routine evaluation of urine concentration/dilution when osmometry is not available.

The Turkish hamster (Mesocricetus brandti) is a photoperiodic species. In this investigation, we characterized the photoperiodic requirements for termination of gonadal refractoriness, defined as the inability of the animal to respond to short-day treatment with gonadal regression. Paired testes weights were reduced to less than 20% of their original weight by 10 wk of 12L:12D treatment. This was followed by spontaneous testicular recrudescence (completed by Week 25 of 12L:12D treatment), the overt indication of refractoriness to short photoperiods. Next, the period of long-day exposure sufficient for termination of refractoriness was determined. Refractory males were exposed to 16L:8D for 5 to 20 wk. Ten weeks of 16L:8D treatment was enough for the animals to regain the sensitivity to a second challenge of 12L:12D treatment. Fifteen weeks of 20L:4D or 16L:8D terminated refractoriness in female Turkish hamsters; 20L:4D therefore was not interpreted as a short day by refractory hamsters. This was unexpected because in photosensitive animals this photoperiod acts like a short day, causing gonadal regression. These results suggest that Turkish hamsters are similar to Syrian hamsters in that both species require two or more months of long days in summer to recover sensitivity to the short days of the following fall.