Photometric Readings Research Articles

Formulation of Chemically Defined Media and Growth Evaluation of Ligilactobacillus salivarius ZJ614 and Limosilactobacillus reuteri ZJ625.

Lactic acid bacteria are increasingly becoming important dietary supplements due to their health benefits when consumed in adequate quantity. The increasing attention on these important microbes has necessitated an in-depth understanding of their physiological processes, such as nutritional requirements and growth patterns, to better harness their probiotic potentials. This study was carried out to determine the nutritional requirements for the growth of L. salivarius ZJ614 and L. reuteri ZJ625 from a chemically defined medium and evaluate growth kinetics by fitting different sigmoidal growth models. The complete CDM contains 49 nutritional ingredients such as glucose, Tween 80®, mineral salts, buffers, amino acids, vitamins, and nucleotides at defined concentrations. In addition, the minimal nutritional requirements of the isolates were determined in a series of single-omission experiments (SOEs) to compose the MDM. Growth curve data were generated by culturing in an automated 96-well micro-plate reader at 37°C for 36 h, and photometric readings (optical density: OD600) were taken. The data were summarized in tables and charts using Microsoft Excel, while growth evaluation was carried out using open-source software (Curveball) on Python. The results revealed that omission of the amino acids, vitamins, and nucleotides groups resulted in 2.0, 20.17, and 60.24% (for L. salivarius ZJ614) and 0.95, 42.7, and 70.5% (for L. reuteri ZJ625) relative growths, respectively. Elimination of the individual CDM components also indicates varying levels of growth by the strains. The growth curve data revealed LogisticLag2 and Baranyi–Roberts models as the best fits for L. reuteri ZJ625 and L. salivarius ZJ614, respectively. All the strains showed appreciable growth on the CDM and MDM as observed in de Man–Rogosa–Sharpe (MRS) broth. We also described the growth kinetics of L. reuteri ZJ625 and L. salivarius ZJ614 in the CDM, and the best models revealed the estimated growth parameters.

Current problems of dynamics of moons of planets and binary asteroids based on observations

The general approach to studying the dynamics of moons of planets and asteroids consists in developing more and more accurate models of motion based on observational data. Not only the necessary ephemerides, but also some physical parameters of planets and moons are obtained this way. It is demonstrated in the present study that progress in this field is driven not only by the increase in accuracy of observations. The accuracy of ephemerides may be increased by expanding the observation time interval. Several problems arise on the way toward this goal. Some of them become apparent only when the procedure of observational data processing and use is examined in detail. The method used to derive astrometric data by processing the results of photometric observations of mutual occultations and eclipses of planetary moons is explained below. The primary contribution to the error of astrometric results is produced by the unaccounted noise level in photometric readings and the inaccuracy of received values of the albedo of moons. It is demonstrated that the current methods do not allow one to eliminate the noise completely. Extensive additional photometric measurements should be performed at different angles of rotation of moons and in different spectral bands of the visible wavelength range in order to obtain correct values of the albedo of moons. Many new distant moons of the major planets have been discovered in the early 21st century. However, the observations of these moons are scarce and were performed over short time intervals; as a result, some of the moons were lost. The necessity of further observations of these Solar System bodies is pointed out in the present study. Insufficient knowledge of asteroid masses is an obstacle to improving the accuracy of the ephemerides of Mars. The basic method for determining the masses of large asteroids consists in analyzing their influence on the motion of Mars, the Earth, and spacecraft. The masses of more than 100 large asteroids were determined this way. One of the principal techniques for Earth-based measurement of the masses of asteroids involves astrometric observations of binary asteroids. The determination of relative coordinates is made rather difficult by the apparent proximity of components. The success of these efforts depends on the availability of instrumentation and the expertise of observers skilled in adaptive optics and speckle interferometry. Collaboration between different research teams and observers is absolutely necessary.

Wavelength Anomalies in Ultraviolet-Visible Spectrophotometry

Spectral scans of atomic line emission sources with a Shimadzu UV2101PC spectrophotometer show that the nominal wavelength depends upon the instrumental slit width, the wavelength sampling interval, and for some slit widths, also on the specified spectral range. The range dependence is manifested as a smoothing that occurs when the range includes >65 sampled wavelengths, and it affects both the wavelength and the line shape. For spectra not subject to this smoothing, the wavelength error looks like a one-sample misassociation of the wavelength and photometric readings. However, the instrument does reliably move to a specified wavelength, independent of the scan parameter settings. These behaviors do not seem to be documented anywhere but have been present in the software for operating this instrument for about two decades.

High-Beam Usage on Low-Volume Rural Roads in Texas

This study evaluated high-beam usage on low-volume roadways in Texas. Most previous studies used a subjective approach to determine high-beam usage that involved a stationary observer or an observer driving around the study section. For more efficient data collection, this study used photometric readings as the methodology. This approach allowed for a quantitative measure of high-beam use, in that it did not rely on an observer's opinion as to whether the headlamps were on high or low beam. Preliminary data collection was conducted as part of the study to estimate the threshold high-beam illuminance value; these illuminance data showed moderate use of high beams on low-volume, rural two-lane highways, with 42% of the free-flow drivers using high beams. There was a wide variation in high-beam use between sites, so site characteristics were reviewed to identify potential reasons for this variation. The data were fit to a logistic regression model to estimate the impact of various site characteristics on a driver's decision to use high beams. The results showed that vehicle speed, paved surface width, number of access points within 1,000 ft of the site, and presence of horizontal curves within 1 mi of the site were statistically significant factors that contributed to the probability of high-beam use. The results also showed that higher vehicle speeds, narrow paved surfaces, presence of horizontal curves, and few or no access points led to a higher probability of high-beam use. These results are intuitive and support the observations made in the exploratory data analysis.

Evaluation of Metabolic Control in Type 1 (Insulin-Dependent) Diabetic Patients by Estimation of Serum Fructosamine*

The method of Johnson et al. (1982) for the estimation of non-enzymatically glycated serum proteins (fructosamine test) was critically evaluated and modified with respect to photometric readings, incubation conditions, and standardization of the procedure. With this modified method, serum fructosamine concentrations were estimated in type 1 (insulin-dependent) diabetic patients whose glycemic control ranged from strictly to poorly controlled and in normoglycemic healthy control subjects. The mean fructosamine concentrations were for the control group (n = 52) 2.17 mmol/l (range 1.73-2.61 mmol/l) and for the diabetic patients (n = 432) 2.87 +/- 0.60 mmol/l (range 2.27-3.25 mmol/l). There were significant differences in fructosamine concentrations among the diabetic patients, corresponding to the degree of metabolic control. Serum fructosamine levels were closely correlated to the HbA1 levels. Compared with HbA1, fructosamine reflects short-term metabolic changes and appears to be an useful index of short-term glycemia.

Diabetic erythrocytes test by correlation coefficient.

Even when a healthy individual is studied, his/her erythrocytes in capillaries continually change their shape in a synchronized erratic fashion. In this work, the problem of characterizing the cell behavior is studied from the perspective of bounded correlated random walk, based on the assumption that diffractometric data involves both deterministic and stochastic components. The photometric readings are obtained by ektacytometry over several millions of shear elongated cells, using a home-made device called Erythrodeformeter. We have only a scalar signal and no governing equations; therefore the complete behavior has to be reconstructed in an artificial phase space. To analyze dynamics we used the technique of time delay coordinates suggested by Takens, May algorithm, and Fourier transform. The results suggest that on random-walk approach the samples from healthy controls exhibit significant differences from those from diabetic patients and these could allow us to claim that we have linked mathematical nonlinear tools with clinical aspects of diabetic erythrocytes’ rheological properties.

Self-organizing dynamics of human erythrocytes under shear stress

The characterization of the erythrocytes’ viscoelastic properties is studied from the perspective of bounded correlated random walk (Brownian motion), based on the assumption that diffractometric data involves both deterministic and stochastic components. The photometric readings are obtained by ektacytometry over several millions of shear elongated cells, using a home-made device called Erythrodeformeter. The results suggest that the samples from healthy donors are intrinsically unpredictable (ordinary Brownian motion), while when studying beta thalassemic samples, these exhibit not only a great sensitivity to initial conditions (fractional Brownian motion) but also chaotic behavior. These results could allow us to claim that we have linked nonlinear tools with clinical aspects of the erythrocytes rheological properties.

Selective Influence of Dentin Thickness upon Cytotoxicity of Dentin Contacting Materials

The effect of three dentin contacting materials on three-dimensional cultures of pulp-derived cells was evaluated in a dentin barrier test device. The test materials (Syntac Classic, Prompt L-Pop, Vitrebond) were applied on dentin disks of different thicknesses ranging from 100 to 500 μm. After 24 h of exposure with and without perfusion of the test chamber, cell survival was evaluated using the MTT assay and related to a nontoxic control material. Syntac Classic decreased cell activity significantly (p ≤ 0.0003), independently of the dentin thickness. For Prompt L-Pop and Vitrebond a significant influence of dentin thickness was found on the cell reaction. After exposure of the control material, photometric readings showed no dependency of the cellular reaction on dentin thickness (p > 0.05). It could be demonstrated that dentin acts as a barrier, decreasing the elicited cytotoxicity with increasing thickness. This effect is material related, showing little influence for the nontoxic or the glutaraldehyde containing material.

Viscoelasticity: Fractal parameters studied on mammalian erythrocytes under shear stress

In this work, experimental determinations are carried out using a home-made device called an erythrodeformeter, which has been developed and constructed for rheological measurements on red blood cells subjected to definite fluid shear stress. A numerical method formulated on the basis of the fractal approximation for ordinary and fractionary Brownian motion1 is proposed to evaluate the viscoelastic behavior of mammalian erythrocyte membranes. The diffraction pattern, which is circular when the mammalian erythrocyte membranes are at rest, becomes elliptical when the cells undergo shear stress. Photometric readings of light intensity variation along the major axis of the elliptical diffraction pattern are recorded during the creep and recovery process. These data series are used to calculate, fractal rheological parameters of self-affine Brownian motion on the erythrocytes, averaged over several millions of cells. Three different parameters over the time dependent process could be obtained, which are: correlation coefficient , correlation integral, andK2-entropy, and very different results were obtained.

Evaluation of gray scale steps on Scheimpflug photographs.

A method for the calibration of gray scale density in a Scheimpflug photograph was established. Based on the result of statistical analysis, it was found that variability in the film emulsion was insignificant if the measuring area > or = 0.01 mm2. Each lens image should be calibrated with the reference gray scale in the same photograph. Photometric readings of the lens image was converted to gray scale levels. This conversion can be obtained from fitting photometric readings of the gray scale as a function of gray scale steps with a third order polynomial. Adopting this calibration procedure, 95% of estimated nuclear densities are within +/- 3-5% of the real value.

Shear-Induced Structural Changes Observed in Concentrated Suspensions of Binary Blends of Fluorescent Particles of Differing Size and Color

AbstractShear-induced structural changes were observed in suspensions of binary blends of fluorescent particles of differing size and color. Median particle size ranged from 8.3 to 13.7 microns for the nearly spherical fluorescent particles. Concentrated aqueous suspensions were studied under shear flow in a Couette fixture modified to accommodate a fused silica cup. The color of the fluorescent particle blends was observed through the cup wall using photometric methods. Suspension color near the cup wall depended upon shear rate. A color shift occurred near the shear thinning to shear thickening transition. With increasing shear rate, the color contribution from the larger particles increased as the thickening transition occurred. Draining films of these suspensions on a flat fused silica plate were also studied using photometric readings from both the free surface and through the silica plate. Color measurements indicated highly non-uniform particle size distributions within the draining films, which varied with drain time.

Detection of Cysticercus cellulosae antigens in cerebrospinal fluid by dot enzyme-linked immunosorbent assay (Dot-ELISA) and standard ELISA.

The dot enzyme-linked immunoassay and standard enzyme-linked immunoassay were used to detect Cysticercus cellulosae antigens in cerebrospinal fluid of patients suffering with neurocysticercosis. Using the dot enzyme-linked immunoassay, 10 of 17 patients (59%) were positive at a reciprocal titer of 128 (range 128-1,024). In the standard assay, 13 of 17 (77%) were positive (range 128-512). Specificity was 100% in both assays using 48 cerebrospinal fluids from patients with various central nervous system infections. The quantification of antigens in cerebrospinal fluid using standard assay and photometric readings showed a range of 17 to 138 ng/ml. The results indicate that both assays are sensitive, specific, and economical for the diagnosis of neurocysticercosis.

Evaluation and interpretation of grain density autoradiographs by reflectance photometry.

The tritium content of nervous tissue sections is calculated from grain-density of autoradiograph without loss in anatomical information. The calculation is not based on determination of (expected) grain numbers but on photometric measurements (SKphot), interpreted as the result of the function of exposure time (T) and incorporated activity (beta): SKphot = f(T, beta). As experimental radiation standards homologous material (optic nerve preparations) with different activities determined by liquid scintillation counting has been used. Exposure times between 12 h and 28 weeks for these preparations with known radioactivities yielded a set of curves (nomogram) relating photometric values of exposure times. At any given exposure time the knowledge of photometric readings and related radioactivities within that set of curves enabled the development of a function covering all photometer readings within the range of the nomogram. Thus, any photometric reading could be correlated to the corresponding radioactivity. Such a function has been applied for the transformation of photometric values obtained from particular brain-section areas exposed for 16 weeks. Since the results are given in Bq, they may be related and, if necessary, corrected to results obtained by other tritium detection methods. Terminology used in the text: experimental radiation source = experimental standards prepared from optic nerve sections; standard radiation source = polymer reference source.

Correction for the inherent error in optical density readings

Except at very low levels, uncorrected photometric determination of bacterial cell densities showed a decreasing proportionally to actual cell density or dry weight. A standard curve was prepared to convert photometric readings to truly proportional optical density values. With one dry weight determination, optical density values may be converted to absolute dry weight values.

A new method for automatic quantitation of the fluorochromatic microcytotoxicity test

Automatic quantitation of the fluorochromatic microcytotoxicity test was obtained by increasing the emission ratio of the sample over background. This ratio was increased by washing and removing the fluorescein which had been released from dead cells into the surrounding media. The fluorescence remaining in the living cells was then measured on a microscope spectrophotometer. The plates, each containing 60 wells, were positioned for viewing on a new semiautomatic stage which can be easily interfaced to a small computer for rapid scoring ( 1 min 20 sec 60 wells ). Good correlation existed between visual scores and photometric readings.

The correlation of individual results in laser microanalysis applied to histological slices.

This work is a continuation of investigations concerning the applicability of laser analysis in histochemical techniques (Kozik et al., 1970a, b; Kozik et al., 1971a, b).Agar standards containing known amounts of Pb were subjected to laser microanalysis and optical densities of the resulting Pb spectral bands as well as volumes of the resultant craters were determined.—Based on mathematical considerations and equation has been educed by means of which the experimentally obtained photometric readings may be converted into densities corresponding to mean crater volumes. In that way it is possible to eliminate inconveniences resulting from diversity of individual crater volumes and from eventual differences in the degree of atomic excitation between samples. Using this method, the concentrations of the investigated element in histological slices become expressed in percentages.

Further investigations concerning the applicability of laser analysis in quantitative histochemistry.

Further investigations on the applicability of the laser technique for qantitative purposes in histochemistry were conducted. Special attention has been paid to the relationship between the volume of the crater burnt out in the tissue by laser ray treatment and the photometric readings of the spectral bands. A statistical evalution of the measurements of crater volumes for quantitative histochemistry as well as determination of the error of the former method used and previously described (Kozik et al., 1970b) have been performed. Special agar standards containing known amounts of Pb(NO3)2 and appropriately prepared photographic plates were used. From the results obtained it appeared that the variances calculated for the differences between density of spectral bands for the Pb present in the investigated sample and the density of the respective band for the Ag present in the photographic plate fall in the range of between 14.1 and 19.7%, whereas the error of the method in which the density of spectral bands was related to the crater volumes covered a range from 3.45–7.7%.

Preparation of histochemical sections for quantitative determination of acid phosphatase activity by means of laser microanalysis.

Based on former experiments dealing with a quantitative assay of acid phosphatase (acP) activity in histological sections by means of a laser microanalysis. The authors present results of investigations concerning optimal conditions needed for this purpose. The investigations were performed on rat liver sections. The realtion between incubation time and depth of acP reaction appearing in tissue blocks was investigated along with the dependence of photometric readings on thickness of histological sections and on incubation times. From results of experiments it appears that optimal conditions for quantitative determination of acP activity using the proposed laser method are provided by sections 30 to 50 μ in thickness which have been incubated in the substrate containing medium for 45 min. Sections thinner than 30 μ are not recommended for quantitative assay with this method because of low accuracy of readings caused by too low amounts of reaction product present there.

Simultaneous Determination of Calcium and Magnesium of Serum by a Single Chelometric Titration

Abstract Titration of a trichloracetic acid filtrate of serum with EDTA is carried out at pH 9.8 using an excess of Calmagite indicator. Successive photometric readings of percentage transmission, made with an EEL titrator, are plotted against the volume of EDTA added. There is very little change at first while calcium is being complexed; the reading then decreases rapidly while magnesium is being titrated, followed by a flattening of the curve at completion of the titration. Hence, two sharp "breaks" are obtained in the titration curve, the first corresponding to the amount of calcium and the second to the amount of magnesium.

Radiation Beam Mapping with Photographic Film

Mapping the intensity distribution across a radiation beam by means of photographic film is convenient and inexpensive, but the question of accuracy of this method requires investigation. An experiment was carried out at the National Bureau of Standards to examine, with film, the uniformity of some of the x- and γ-ray beams used in calibration work. By exercising certain precautions in film selection, positioning, processing, and photometric measurement, it was possible to determine the relative intensity of radiation across the beams with an accuracy of 1 per cent. A commercial x-ray film type was chosen, which, when exposed to Co60 γ-radiation and, for maximum contrast, processed for twice the prescribed time in a commercial x-ray developer, showed a fog density level of only 0.11 and a linear response up to a density level of 3.5, within the accuracy of the photometric readings. This film was available in 14 × 17-inch size, in individual envelopes with center position and orientation marked on the outside for easy and accurate positioning. During the exposure, the film was held rigidly between layers of plastic, thick enough for electronic equilibrium, in a plane perpendicular to the central ray of the beam. All other supporting materials were kept outside the beam, to avoid errors due to radiation scattering. Commercial x-ray developer was used for processing for ten minutes at 20° C. and, with vigorous, random, manual agitation, produced highly uniform densities on the large sheets of film. Certain photographic artefacts were avoided by using fresh developer, stop bath, and fixer, and by thorough washing and uniform drying. For the photometric measurement, a photoelectric densitometer was used, whose inherent accuracy over a density range from 0 to 5.00 was within 0.02 density units. Readings over a relatively narrow spread of densities were found to be reproducible within the reading accuracy that was limited by the resolution of the densitometer scale. With this procedure, relative intensity readings at any one point on several film sheets, exposed identically at a 1-meter distance in a Co60 γ-ray beam and processed in various orientations in the developer, showed agreement within 0.5 per cent. A plot of the intensity distribution for one direction across the beam is shown in Figure 1, A. The points represent average readings at the various positions on three different film sheets. More than 400 densitometric readings over a central area of 8 × 8 cm. of the exposed films showed a root mean square deviation of 0.7 per cent. This is within the 1 per cent accuracy limit of the photographic method. For this particular beam, only beyond a distance of 10 cm. from the center did the intensity decrease by a statistically significant value.