Initial Set Of Measurements Research Articles

The effect on the five FDA soft contact lens material types of prolonged exposure to phospholipid-based eye drops.

The aim of this study was to assess the effects of regular phospholipid tear supplement application on five soft contact lens materials (FDA Types I-V). Twenty unworn lenses of each lens type were assessed and given an identification number. An initial set of measurements was made on each lens before being immersed in the phospholipid tear supplement solution for one hour. After one hour, the lens was removed, gently rinsed in saline, and the measurements were repeated. This process was repeated for each lens, of each type. Each lens parameter was assessed in the sequence: Refractive Index (% H2O), Dioptric Power (BVP), Lens Diameter (OD), and Lens Curvature (BCOR). All measurements of % H2O, BVP, OD and BCOR did not differ between baseline and after lenses being immersed in the phospholipid tear supplement solution for one hour [all soft contact lens materials (FDA Types I-V) p > 0.05]. However, in the type IV lenses, a statistically significant change in the % H2O was found. Only a 1% reduction was observed, and, in the investigator's opinion, the significance of these results is due more to a statistical anomaly produced by having very repeatable measurements showing very little variation. The phospholipid tear supplement solution did not adversely change the physical parameters of unworn soft contact lenses, of the five FDA Types, to the extent that would be considered clinically significant.

Picometer sensitivity metrology for EUV absorber phase

With growing interest in EUV attenuated phase-shift masks due to their superior image quality for applications such as dense contact and pillar arrays, it is becoming critical to model, measure, and monitor the intensity and relative phase of multilayer and absorber reflections. We present a solution based on physical modeling of reflectometry data, which can achieve single picometer phase precision and sensitivity to changes in average film thickness below one atomic monolayer. We measure absorber and multilayer reflectivity to determine thin-film parameters with a multidimensional optimization and then acquire a new measurement of either multilayer or absorber to determine perturbations in surface contamination thickness. While it is difficult to assess the accuracy of the first step, the simplicity of the second step allows us to characterize our sensitivity to changes in contamination thickness. We apply this analysis using an initial set of measurements and repeated measurements after a period of storage. For the multilayer, the total contamination growth was 1068 pm, which occurred almost exclusively during storage (1085 pm) and decreased very slightly during repeated measurements (−17 pm). For the absorber, the behavior was quite different, with a total growth of 126 pm, which occurred much less during storage (28 pm) and primarily during repeated measurements (98 pm). Ultimately, the change in relative phase (absorber minus multilayer) was −0.86 deg for the multilayer and −1.12 deg for the absorber. We estimate the precision of the surface contamination measurement to be 3σ < 6 pm for measuring thickness and 3σ < 0.2 deg for measuring phase.

Measurement of Pressure Field on Stationary Rotary Wing Model for Further Computation of Chaff Cloud Bloom

This article describes the current situation in the area of electronic warfare. Aircraft protection can be greatly utilised not only in military but also in civilian applications. Active radar signal jamming methods are costly and therefore, aircraft protection using Chaff jamming increases efficiency, application variability and makes aircraft protection affordable. The article describes Chaff and the initial set of measurements designed for measuring aerodynamic pressure around a stationary helicopter model. This data lays foundations for the direction of further development, which is introduced at the end of the article.

A fast heuristic optimization algorithm for measurement placement in distribution system state estimation

An accurate, real‐time estimation of the states of a power distribution system is highly desirable but hard to achieve because of the complexity of the network and the relative inefficiency of the measuring system. To increase the efficiency, this paper analyzes the mathematical relationship between the measurement errors and estimation errors of the state vector using the classic weighted least square method. Then a heuristic algorithm is proposed to improve the accuracy by optimizing the deployment of the real‐time measuring points, which is based on the deterministic factors of the measuring points/branches over the system state. The basic implementation starts with an initial measurement set and replaces the least important branches in the set with the most important branches outside the set using iterative optimization. The algorithm was tested in the IEEE 14‐bus and 33‐bus distribution systems and achieved 50% increase in accuracy at much lower computational cost compared with exhaustive search. Moreover, the proposed algorithm has also been compared with representative and widely used evolution algorithms such as particle swarm optimization and quantum‐behaved particle swarm optimization. This comparison shows that our method can achieve stable and comparable accuracy with a speed at least 10 times higher. The performance of our method can be even better with increasing network size. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Design and performance of a novel magnetocaloric heat pump

The design and preliminary results of an active magnetic refrigeration prototype for room temperature cooling applications are investigated. The physical prototype along with its operational and measurement envelopes are described. General design goals included: A wide range of cycle parameter control, independent fluid and magnetic circuits, extensive measurement capability, and compact overall design. An initial set of measurements has been made with Gadolinium particulate of an industrial purity. The maximum no-load span recorded was 21 K and the maximum power recorded was 26 W at a span of 1 K. Additionally, three different cyclical parameters have been varied to help determine the optimal cycle for such a machine. The unique modularity and control of this system will allow for a detailed understanding of the operation of commercial active magnetic regeneration designs.

Effect of colloidal silica on rheological properties of common pharmaceutical excipients

In pharmaceutical industry, the use of lubricants is mostly based on historical experiences or trial and error methods even these days. It may be demanding in terms of the material consumption and may result in sub-optimal drug composition. Powder rheology enables more accurate monitoring of the flow properties and because the measurements need only a small sample it is perfectly suitable for the rare or expensive substances. In this work, rheological properties of four common excipients (pregelatinized maize starch, microcrystalline cellulose, croscarmellose sodium and magnesium stearate) were studied by the FT4 Powder Rheometer, which was used for measuring the compressibility index by a piston and flow properties of the powders by a rotational shear cell. After an initial set of measurements, two excipients (pregelatinized maize starch and microcrystalline cellulose) were chosen and mixed, in varying amounts, with anhydrous colloidal silicon dioxide (Aerosil 200) used as a glidant. The bulk (conditioned and compressed densities, compressibility index), dynamic (basic flowability energy) and shear (friction coefficient, flow factor) properties were determined to find an optimum ratio of the glidant. Simultaneously, the particle size data were obtained using a low-angle laser light scattering (LALLS) system and scanning electron microscopy was performed in order to examine the relationship between the rheological properties and the inner structure of the materials. The optimum of flowability for the mixture composition was found, to correspond to empirical findings known from general literature. In addition the mechanism of colloidal silicone dioxide action to improve flowability was suggested and the hypothesis was confirmed by independent test. New findings represent a progress towards future application of determining the optimum concentration of glidant from the basic characteristics of the powder in the pharmaceutical research and development.

Accurate polarimeter with multicapture fitting for plastic lens evaluation

Due to their manufacturing process, plastic injection molded lenses do not achieve a constant density throughout their volume. This change of density introduces tensions in the material, inducing local birefringence, which in turn is translated into a variation of the ordinary and extraordinary refractive indices that can be expressed as a retardation phase plane using the Jones matrix notation. The detection and measurement of the value of the retardation of the phase plane are therefore very useful ways to evaluate the quality of plastic lenses. We introduce a polariscopic device to obtain two-dimensional maps of the tension distribution in the bulk of a lens, based on detection of the local birefringence. In addition to a description of the device and the mathematical approach used, a set of initial measurements is presented that confirms the validity of the developed system for the testing of the uniformity of plastic lenses.

The Helical Structure of Sweat Ducts: Their Influence on the Electromagnetic Reflection Spectrum of the Skin

The helical structure of human eccrine sweat ducts, together with the dielectric properties of the human skin, suggested that their electromagnetic (EM) properties would resemble those of an array of helical antennas. In order to examine the implications of this assumption, numerical simulations in the frequency range of 100-450 GHz, were conducted. In addition, an initial set of measurements was made, and the reflection spectrum measured from the skin of human subjects was compared to the simulation results. The simulation model consisted of a three layer skin model (dermis, epidermis, and stratum corneum) with rough boundaries between the layers and helical sweat ducts embedded into the epidermis. The spectral response obtained by our simulations coincides with the analytical prediction of antenna theory and supports the hypothesis that the sweat ducts can be regarded as helical antennas. The results of the spectrum measurements from the human skin are in good agreement with the simulation results in the vicinity of the axial mode. The magnitude of this response depends on the conductivity of sweat in these frequencies, but the analysis of the phenomena and the frequencies related to the antenna-like modes are independent of this parameter. Furthermore, circular dichroism of the reflected electromagnetic field is a characteristic property of such helical antennas. In this work we show that: 1) circular dichroism is indeed a characteristic of the simulation model and 2) the helical structure of the sweat ducts has the strongest effect on the reflected signal at frequencies above 200 GHz, where the wavelength and the dimensions of the ducts are comparable. In particular, the strongest spectral response (as calculated by the simulations and measured experimentally) was noted around the predicted frequency (380 GHz) for the axial mode of the helical structure.

Carbon Isotope Measurements of Surface Seawater from a Time-Series Site Off Southern California

We report carbon isotope abundances of dissolved inorganic carbon (DIC) in surface seawater collected from a time-series site off the Newport Beach Pier in Orange County, California. These data represent the first time series of Δ14C data for a coastal southern California site. From a suite of samples collected daily from 16 October to 11 November 2004, Δ14C values averaged 32.1 ± 4.4‰. Freshwater input from the Santa Ana River to our site caused Δ14C and δ13C values to decrease. Since this initial set of measurements, a time-series site has been maintained from November 2004 to the present. Surface seawater has been collected bimonthly and analyzed for Δ14C, δ13C, salinity, and ΣCO2 concentrations. Water samples from the Santa Ana River were collected during the wet season. California sea mussels and barnacle shells, ranging from 4 to 6 months old, were also collected and analyzed. Results from May 2005 to January 2008 show no long-term changes in δ13C DIC values. Δ14C DIC values over the 2005–2006 period averaged 33.7‰; high Δ14C values were observed sporadically (every 6–7 months), suggesting the presence of open water eddies at our site. Finally, in 2007, a stronger upwelling signal was apparent as indicated by correlations between Δ14C, salinity, and the Bakun index, suggesting that the Δ14C record is an indicator of upwelling in the Southern California Bight.

Minimizing the integer ambiguity search space for RTK

Differential GPS carrier phase measurements have much lower noise and multipath error than that of pseudorange measurements. The result is centimeter accuracy for Real-Time Kinematic (RTK). However, the measurement of the carrier phase has a constant unknown integer ambiguity. Several technical issues are related to solving the integer ambiguity correctly. They are: proper stochastic model, search space definition and initialization, search space reduction, state and standard deviation calculation, validation and rejection criteria for the unique and correct candidate. Search space reduction is critically important. It not only affects the ambiguity resolution speed, but also defines the ambiguity resolution success rate. The smaller the search space, the easier it is to find the unique and correct candidate set. The paper analyzes the integer ambiguity search space in its residual domain. The search space is minimized by: Analyzing the maximum independent integer ambiguity measurement set theoretically; Selecting the best initial measurement set that minimizes the search range of each satellite in the set and reduces the error effects from noise that may cause the wrong integer ambiguity solution for the remaining satellites not contained in the initial measurement set.

EFFECT OF LIANA CUTTING ON TREE REGENERATION IN A LIANA FOREST IN AMAZONIAN BOLIVIA

Lianas, woody climbing plants, are a conspicuous component of tropical forest canopies that might affect prevailing conditions in the forest floor and thus impact tree seedling regeneration. The effects of lianas on tree seedling survival, growth, and density were studied in a lowland liana forest in Bolivia. Gravimetric soil water content and canopy openness were measured to evaluate whether these factors changed as a result of liana cutting. I established 24 square plots of 900 m2 each, and after an initial set of measurements, all lianas were cut in half of them, while the others plots were used as controls. Tree seedling growth and survival of two tree species were evaluated: Clarisia ilicifolia and Astronium fraxinifolium. Eighteen months after liana cutting, seedlings in liana-cut plots grew significantly taller and produced more leaves than did seedlings in control plots, but survival was not affected by treatment. Seedling growth following liana cutting was significantly higher in A. fraxinifolium...

Variability of blood pressure response to orthostatism and reproducibility of the diagnosis of orthostatic hypotension in elderly subjects.

Orthostatic hypotension (OH) is a major problem in the elderly population. Its diagnosis is based on measurement of the blood pressure (BP) response to orthostatism (BPRO). This study investigates the within-day and day-to-day variability of the BPRO and the reproducibility of the diagnosis of OH in this population. BP was measured in the supine position and after 1 and 2 minutes of orthostatism in 53 consecutive elderly patients (43 women and 10 men aged 83.7 +/- 9.5 years) of an intermediate care geriatric ward. BPRO was assessed 4 times on the same day (8-9 AM, 10-11 AM, 1-2 PM, and 5-6 PM) and twice more on another day of the same week (8-9 AM and 1-2 PM). There were significant within-day differences between the four orthostatic changes in systolic BP (OCs, supine minus standing systolic BP) after 1 minute or 2 minutes (p < .05). Day-to-day differences between the OCs measured at the same times were not significant. OH defined as an OCs of 20 mm Hg or more at 1 or 2 minutes of orthostatism, was found in ten cases (19%) in the initial set of measurements on the first day. A cumulative diagnosis of OH after the six BPRO tests was found in 23 cases (43%). The reproducibility of the diagnosis of OH was mild or poor (all kappa values were below 0.47). BPRO exhibits significant within-day variability in elderly patients. Within-day and day-to-day reproducibility of the diagnosis of OH, based on conventional criteria, were found to be poor.

Reproducibility of frame positioning for fractionated stereotactic radiosurgery

Fractionated stereotactic radiation therapy is a useful new approach for treating a number of intracranial neoplasms including meningiomas, pituitary adenomas, craniopharyngiomas, and recurrent gliomas. For the majority of these we employ a conventional fractionation scheme of 180 cGy per fraction for 25 to 30 fractions, using a modified Gill–Thomas–Cosman (GTC) relocatable frame to accommodate fractionated delivery. The GTC system uses a custom acrylic dental appliance to set the frame position and an occipital plate and Velcro straps fix the head in place. Daily reproducibility is evaluated through use of a “depth helmet,” a plastic hemispherical shell containing 25 holes at regularly spaced intervals. The depth helmet attaches to the GTC frame and the distance from the shell to the patient's head is recorded at each of the 25 positions. This paper describes a new simplified approach to the quantitative assessment of day-to-day variability in head fixation using the depth helmet measurements. This approach avoids the need to try and decide on the relative merit of 25 numerical differences at each fitting and provides a straightforward mathematical and conceptual framework for the description of fit and clinical decision making. The mathematical analysis and computer program we have developed uses all 25 measurements to provide a single three-dimensional displacement vector as well as displacement values in the three principal patient dimensions. Measurements at each of the 25 depth helmet positions are automatically separated into three principal axes corresponding to the patients left/right (x), anterior/posterior (y), and superior/inferior (z) using the spherical relations: x = r sin(Φ) cos(θ), y = r sin(Φ) sin(θ), z = r cos(Φ), where θ and Φ are the polar and azimuthal angles respectively and ris the distance from the center of the depth helmet to the surface of the patient's head. For each patient, a set of initial measurements is taken at the CT scanner with the patient in the treatment (supine) position. Because treatment planning is based on the CT scan, this serves as the baseline from which subsequent deviations are recorded. In an analysis of our first 30 patients representing over 750 fractions, the mean RMS deviation, that is, the mean three-dimensional displacement from baseline, was 0.468 ± 0.296 mm. Among individual patients the range was 0.169 mm to 1.438 mm. A closer analysis suggests that in-plane (AP/PA-lateral) deviations occur randomly. Deviations along the superior/inferior direction are greater than those in-plane, and in several patients a small shift along this axis, possibly due to a loosening or stretching of the Velcro straps, has been noted over time. We have found our method to be a useful indicator of day-to-day reproducibility, allowing ready identification and correction of three-dimensional shifts relative to the patient axes. Based on our initial analysis, we can now define quantitative limits of acceptability in repositioning for subsequent fractionated delivery.

Measurements and modeling of sound propagating into unconsolidated water-saturated porous media in a laboratory environment

Three models of sound propagating into and within a water-saturated sandy bottom are compared to measurements made in the NRL shallow water laboratories. An initial set of measurements was made in a manufactured 212-μm mean diameter sand, which was washed and filtered, to quantify sound penetration as a function of incident angle and interface roughness, as well as to identify the wave types generated within a water-saturated sandy bottom. Measurements have also been made of sound propagation within a water-saturated sandy bottom, which employed a specialized set of transducers to generate and measure compressional waves and a second set of transducers to generate and measure shear waves. Measurements have also been made in a 525-μm mean diameter water-saturated sand. All of the above measurements are compared to a fluid bottom model and a Biot media model, both of which characterize the sound propagating within a water-saturated sandy bottom. In addition, the measurements of sound penetration into the standy bottom are compared to roughened interface scattering models. [Work supported by NRL and ONR.]

Analysis of laboratory measurements of sound propagating into an unconsolidated water-saturated porous media

A series of measurements in the NRL shallow-water laboratory have been conducted to understand the propagation of sound into and within an unconsolidated water-saturated porous medium. The initial set of measurements was taken to quantify sound penetration as a function of incident angle and interface roughness and to identify the types of waves generated within the water-saturated sandy bottom. These investigations included two-dimensional synthetic array measurements for both a smoothed and a roughened interface. Additionally, above interface and buried source, one-dimensional synthetic array measurements were taken to investigate specifically the types of compressional waves generated within the sandy bottom. To complete the physical characterization of the wave speeds propagating in the bottom, measurements of the shear wave speeds have been made. These measurements provide a large data base for analysis to understand the physics of this sandy bottom, which consists of a 3.0-m-deep bed of a manufactured 212-μm mean diameter sand. Analysis of these measurements using Biot models and other fluid models is presented. In addition, analysis of enhanced sound penetration at shallow grazing angles due to a roughened interface is discussed. [Work supported by ONR.]

Three-dimensional instability of the shear layer over a circular cylinder

The instability of the shear layer separated from a circular cylinder was investigated for Reynolds numbers, based on cylinder diameter, from 3500 to 53 000. For this, the most amplified instability frequencies were found and compared against available results for this ReD range. Based on this initial set of measurements, ReD=3500 was chosen for a detailed study of the instability of the separated shear layer to 3-D disturbances. This involved the excitation of plane Kelvin–Helmholtz waves using an acoustic source, and pairs of oblique waves of equal but opposite angles produced by roughness which was distributed evenly along the cylinder span at the separation line. The sensitivity of the shear layer instability to the initial 2-D disturbance amplitude and 3-D disturbance wave angle was documented. The results showed that there exists a most amplified 3-D wave angle (spanwise wave length) for the separated shear layer. The sensitivity to the wave angle agreed well with the linear 3-D stability analysis of a Stuart vortex by Pierrehumbert and Widnall and the numerical simulations of a free shear flow by Rogers and Moser.

Air impedance-tube technique for measuring the acoustic properties of wet sediment samples

An impedance tube ( Brüel &amp; Kjaer type 4002), originally designed for air acoustic measurements, was modified for use in making attenuation measurements on ocean bottom sediment samples. The measurements are made by placing sediment samples in holders terminated by a reflector plate, the length of which is selected to be equal to the sample length times the ratio of the sound velocity in the plate to the approximate velocity in the sediment. Since sound velocities for most sediments vary from about 1300 to 1700 m/sec, it appears that variations in reflectivity with frequency, which are a function of sediment velocity and attenuation, may be measured with this technique. The present technique differs from other methods used for sediment attenuation studies in that measurements are made in air instead of water. To evaluate the method, an initial set of measurements was made to determine the acoustic properties of water-kaolinite mixtures. Preliminary data analysis indicates that the frequency dependence of the acoustic properties of wet sediment samples can be measured over the range from 1 to 10 kHz by using an impedance tube in air, together with a series of different-length sample holders. The results are compared to measurements made with other techniques.