Density of crystalline lens and cornea in different trimesters of pregnancy

PurposeTo evaluate topographic measurements of the anterior segment and densitometric measurements of the cornea and lens by Pentacam HR in different trimesters of pregnancy.MethodsThis prospective study included 150 healthy pregnant women in their first, second, or third trimester (Groups 1, 2 and 3, respectively) and 54 non-pregnant healthy women (Group 0). Topographic measurements, including central corneal thickness (CCT), corneal volume (CV), anterior chamber depth (ACD), corneal densitometry (CD) and lens densitometry (LD), were done with the Pentacam HR (Oculus, Wetzlar, Germany). The measurement results of the healthy pregnant women and non-pregnant healthy women were compared.ResultsCD values were found in Group 1 to be 13.19, in Group 2 to be 13.16, in Group 3 to be 13.17 and in Group 0 to be 13.22 (p = 0.811). The mean Group 1, Group 2, Group 3 and Group 0 LD-horizontal was 5.40 ± 0.5, 5.47 ± 0.38, 5.53 ± 0.44, 5.36 ± 0.43, respectively. The mean Group 1, Group 2, Group 3 and Group 0 LD-vertical was 5.6 ± 0.43, 5.66 ± 0.32, 5.71 ± 0.40 and 5.5 ± 0.44, respectively. Area LD values were higher in the advanced trimester period, and the only statistically significant difference was between Group 3 and Group 0 (p = 0.025). The difference between three-dimensional (3D) and peak LD values was not statistically significant between the groups (p = 0.89 and p = 0.91, respectively).DiscussionThe Pentacam HR seems to be an important option for the evaluation of LD, CD and topographic measurements of the anterior segment in pregnancy. In the present study, CD and LD, including LD-horizontal, LD-vertical, peak and 3D values, were not significantly different between pregnant women and non-pregnant women.     

Flow regime identification in spouted beds using gamma-ray densitometry

The mixing characteristics, flow patterns and hydrodynamics of gas-solid spouted beds depend on the type of operating flow regime. In the present work, Gamma-Ray Densitometry (GRD) technique has been developed and implemented for the first time to identify different flow regimes and their transition velocities in gas-solid spouted beds. Two spouted beds (0.152 m and 0.076 m diameter) have been used to identify various flow regimes. Three statistical parameters (mean, variance and flow regime indicator (I)) have been applied to analyze the photon counts from GRD. It was found that the implementation of such non-invasive radioisotope based technique, GRD, was successfully able to identify different flow regimes and their transition velocities in gas-solid spouted beds. Flow regimes of packed bed, stable spouting and unstable spouting have been identified in the two studied spouted beds. Furthermore, the stable spouting regime achieved at larger magnitudes of the range of the superficial gas velocity in a larger diameter bed as compared to those in a smaller diameter bed.     

Evaluation of cortical bone by peripheral quantitative computed tomography in continuous ambulatory peritoneal dialysis patients

Several studies have suggested an increased prevalence of osteopenia in dialysis. Peripheral quantitative computed tomography (pQCT) is a new technique that allows the noninvasive evaluation of trabecular and cortical bone separately. The aim of the study was: (1) to evaluate cortical bone by pQCT in continuous ambulatory peritoneal dialysis (CAPD) patients and compare the data with that obtained in healthy controls; and (2) to correlate cortical bone parameters with bone mineral density (BMD) of the lumbar spine and femoral neck and total bone mineral content (TBMC). Cortical bone parameters were obtained in 22 CAPD patients and 27 healthy individuals at the distal radius using a Stratec XCT 960 pQCT machine. In the dialysis patients, we also determined BMD and TBMC by bone densitometry. Dialysis patients, compared with controls, showed a significant reduction in volumetric cortical BMD (VcBMD) (p = 0.04) and cortical thickness (cThk) (p < 0.0001) with a significant increase in radial total cross-sectional area (TA) (p = 0.006), endosteal circumference (p < 0.0001), and buckling ratio (p < 0.0001). In CAPD patients, total time on dialysis correlated negatively with radial total BMD (p < 0.01) and VcBMD (p < 0.01). Age correlated positively with TA (p < 0.01), endosteal (p < 0.01), and periosteal circumferences (p < 0.01). Serum intact parathyroid hormone (PTH) levels correlated positively with endosteal (p = 0.04) and periosteal perimeter (p = 0.01). Total alkaline phosphatase correlated negatively with VcBMD (p < 0.01), and positively with endosteal perimeter (p = 0.02). Total bone mineral content correlated significantly with radial cortical content (p < 0.001), cross-sectional cortical area (cA; p < 0.001), and cThk (p < 0.01) but not with total radial BMD, VcBMD, or buckling ratio. No correlations were found between radial cortical parameters and BMD measured at the lumbar spine or femoral neck. We conclude that dialysis patients show cortical osteopenia with marked cortical thinning partially mediated by PTH action on bone. Total bone mineral content correlated with various radial cortical parameters (content, area, and thickness) but not with others. No correlations were found between cortical bone parameters measured at the peripheral skeleton with areal bone density measured at the axial skeleton. These findings suggest that pQCT may be a new tool in the assessment of bone fragility in dialysis patients.     

Salinity and flow regime independent multiphase flow measurements

For oil production fields, there is a need for downhole measurements of the gas/water/oil multiphase flow. In extreme conditions a relatively simple, robust, and non-intrusive system will be appropriate. A measurement setup that combines multiple gamma beam (MGB) and dual modality densitometry (DMD) measurements, would be able to determine the gas volume fraction (GVF) independently of the flow pattern, and monitor changes in water salinity. MGB measurements of gamma-ray transmission along multiple sections across the oil pipe will provide information on the flow pattern. Whereas the DMD principle will give information on changes in salinity from a combination of transmission and scattering gamma-radiation measurements. In this work we present the results from MGB and DMD measurements of a multiphase flow with high-speed gamma-ray tomograph measurements as reference for the flow pattern. The MGB measurements should enable us to distinguish between stratified or wavy/slug and annular or slug flow. Flow patterns with several minor components distributed evenly over the measurement cross section, like bubble flow, will be interpreted as homogeneous flow. The DMD measurements can be used to monitor salinity changes of the water component for intervals where the GVF is low and the water cut of the liquid is high. Combined with other gauges for water cut measurements, the MGB and DMD measurement setup should improve the multiphase flow measurements, and enable increased oil/gas recovery and production water monitoring.     

Improvement of overlapping nuclear track densitometry

Detection of tracks produced by α particles, protons or nuclear fission fragments in plastic detectors, viz., solid‐state nuclear track detectors, constitutes a very important tool in various areas. It is not easy for humans to count CR‐39 nuclear tracks manually, especially when the track density is very high. An automated computer program called KTTMS2, written in C++ and running with a user friendly interface, has been developed for recognition and parametric measurements of etched tracks in images captured from the surface of solid‐state nuclear track detectors. Well‐known edge detection methods were applied to estimate the precision and accuracy of nuclear track densitometry using the CR‐39 detector. Among the various routine edge detection methods, the Canny method was chosen because it was the most accurate technique. Because accuracy becomes more important as the track density increases, this allows more overlapping tracks to be detected. KTTMS2 (the proposed system) has an efficiency of 95% and can identify the noise as a background track (5%). Experimental results showed that the error percentage was reduced from 7.63% to 3.23% for high‐density tracks when the count was adjusted by the estimated overlapping tracks.     

Resolution abilities and measuring depth of High-Frequency densitometry on wood samples

The High-Frequency (HF) densitometry measures relative density variations on wood samples utilizing the dielectric properties in wood. This method is based on the propagation of an electric stray field through the surface-near region of a wood sample. We studied experimentally the penetration depth and the differentiation abilities of the HF-densitometry method on wood samples. Two experimental approaches showed that penetration depth is related to the geometrical dimensions of the micro-electrode measuring system. Characteristic patterns of the HF-output signal were used to determine the resolution abilities of each HF-probe. Due to a very small integration area geometric structures of earlywood cells of Norway spruce were indicated by stepwise profiles in the HF-output signal pattern. With the High-Frequency densitometry it was possible to distinguish different cell structures due to their variations in wood density up to a resolution of 1 μm. In addition it was possible to determine wood density variations at various resolution levels. Based on the respective resolution abilities and penetration depths of five different purpose-built HF-probes we show the optimal operating conditions for measurements on wood of this indirect densitometry method.     

Optimization of coomassie staining for quantitative densitometry of soybean storage proteins in gradient gel electrophoresis

Soybean (Glycine maxL. Merr., cv. Dare) protein subunits were separated by gradient gel electrophoresis and analyzed by two-dimensional densitometry with computer-aided volume integration. Significant differences in the time required to achieve equilibrium staining with Coomassie Blue were revealed among the various polypeptides. Bands corresponding to lipoxygenase reached staining equilibrium in 2.7 h, whereas longer periods were required for polypeptides of β-conglycinin (5.5 to 6.7 h) and of glycinin (8.6 to 9.2 h). These differences among polypeptides could be attributed in part to changes in gradient concentration within the polyacrylamide gel. Optimal staining intensity among all soluble proteins extracted from soybean seed was reached after staining for 8 h. Shorter than optimal staining times lead to significant underestimation of parameters such as the percentage of β-conglycinin and glycinin of total soluble protein.     

An evaluation of the solid hold‐up distribution in a fluidized bed of nanoparticles using radioactive densitometry and fibre optics

An experimental study was conducted to assess the solid hold‐up distribution in a fluidized bed of zirconia and aluminum nanoparticles. For this purpose, two different techniques, radioactive densitometry and fibre optic measurement, were used. The results showed that while the fluidization of these nanoparticles occurs in the agglomeration state, it performs homogeneously in terms of phase concentration. This matter is important especially when a polymerization reaction should take place uniformly on the surface of nanoparticles, where the monomer is the fluidizing gas. Both techniques presented uniform solid hold‐up distribution over the cross‐section, although the fibre optic method overestimated the overall solid concentration, which was obtained based on bed expansion results. The radioactive densitometry was, however, capable of properly predicting the phase concentration within the bed according to the bed expansion observation. Finally, the effect of bulk density on the fluidization of nanoparticles was discussed by comparing the fluidization of different types of particulate materials.     

A unidirectional temperature gradient stage for solidification studies in aqueous solutions

A low temperature light microscope stage has been designed and fabricated for quantitative analysis of the solidification of aqueous solutions. Thermal boundary conditions are controlled during freezing so as to enable direct comparison of data with complementary theoretical models. Evolution of the temperature distribution within the system is monitored by a one-dimensional thermocouple array, and growth of the phase interface is measured via a displacement transducer. The two-dimensional solution concentration field is assessed by computer densitometric analysis of the grey scale distribution for a light absorbing solute. Experimental and theoretical analyses of freezing processes with the stage correlate well, and the data base is shown to be internally consistent by independent thermal and mechanical measures of the interface velocity.