Equivalent Cylindrical Diameter Research Articles

Does the duration of no-till implementation influence depth distribution of soil organic carbon, hydro-physical properties, and computed tomography-derived macropore characteristics?

No-till (NT) is a sustainable alternative to conventional-till (CT), however, the impacts of NT and its duration on the depth distribution of soil organic carbon (SOC), physical and hydrological parameters are less studied. Therefore, the objective of this study was to evaluate the changes in soil hydro-physical properties and X-ray computed tomography (XCT)-derived macropore characteristics to a depth of 40 cm as influenced by the duration [short-(5-yr) and long-(30 yr) term] of NT practice on a previously conventionally-tilled (CT) soil. The treatments included: CT, initiated in 1991; long-term NT (LTNT),1991; and short-term NT (STNT), 2016 established on silty clay loam soil (Udic Haplustolls). Four replicated intact soil cores were collected from each treatment at 0–10, 10–20, 20–30, and 30–40 cm depths. Data showed that the LTNT stored 23% more SOC stock in the 0–40 cm depth as compared to the CT. The LTNT also increased the total nitrogen (TN) stock, soil water retention (SWR), plant available water (PAW) content, and saturated hydraulic conductivity (Ksat) to the depth of 40 cm as compared to the CT. The LTNT increased the XCT-derived soil macroporosity [pores with > 500 µm equivalent cylindrical diameter (ECD)] and pore connectivity up to 20 cm than the CT. However, the STNT implementation increased the SWR at − 0.6, − 5, and − 30 kPa, pore connectivity, and Ksat only for the 0–10 cm depth than the CT. In addition, PAW showed a high correlation with SOC content [Pearson correlation coefficient (δ) = 0.71], and Ksat was highly correlated with the modulus of XCT-derived Euler-Poincaré characteristic (a measure of local connectivity; δ = 0.61). The study highlighted that pore connectivity and Ksat in surface soil (0–10 cm) were most responsive to the implementation of NT on a previously tilled soil. Data suggest that a longer duration of NT implementation was required to improve the SOC and soil hydro-physical parameters to a deeper soil profile (0–40 cm). Therefore, we conclude that the conversion of tilled soil to NT practice has beneficial effects, depending upon the duration of NT implementation, in enhancing the SOC and hydro-physical conditions, which may help in storing more water in deeper soil for enhanced production.

Relationship between Patient-Dependent Parameters and Radiation Dose Rates Measured around Patients Undergoing PET/CT Imaging Using <sup>18</sup>F-FDG

Objectives: Patients undergoing 18F-FDG PET/CT imaging are considered external radiation sources. Accurate dose rate estimates are important for conducting realistic risk assessments and performing dose reconstruction in cases of accidental exposures. The patient radiation self-attenuation factor is assumed to be a function of the patient’s body size metrics, but we can use these metrics to predict the dose rate around the patients with accuracy. The objective of this work was first to measure the patient attenuation factor by performing direct dose rate measurements from patients undergoing PET/CT imaging studies using 18F-FDG. The second objective was to study the possible correlation between the measured dose rate constant per unit activity from the patients and their body size metrics; five metrics were tested in this work. The last objective was to measure the patients’ voiding factor. Methods: We have measured dose rates at one meter from 57 patients and noted the patient’s height (H), weight (W) and calculated patient size metrics namely: Equivalent Cylindrical Diameter (ECD), Equivalent Spherical Diameter (ESD) and the Body Mass Index (BMI). Results: The measured average dose rate was 92.2 ± 14 μSv·h-1·GBq-1 measured at one meter. Therefore, the dose rate constant of 92 μSv·h-1·GBq-1 proposed by the AAPM, TG-108 report is adequate for radiation protection purposes. There was no statistically significant correlation between the dose rate constant per unit activity and the patient body size metrics. We have measured a patient voiding factor of 0.89 ± 0.06 in comparison with 0.85 recommended by the AAPM. Conclusions: The presented data can be used by medical physicist working in nuclear medicine in formulating more accurate risk estimations resulting from radiation exposure from patients undergoing 18F-FDG PET/CT imaging.

Characterization of highly porous nanoparticle deposits by permeance measurements

Highly porous deposits of flame-made aerosol nanoparticles were formed by filtration through a porous substrate (α-alumina, average pore diameter 3.7μm). The aerosol was characterized by transmission electron microscopy (TEM) and scanning mobility particle sizer (SMPS) showing average primary and agglomerate particle sizes of 4.1 and 30nm, respectively. The analysis of the cake structure (determination of pore-size, dec, and porosity, εc) was carried out by two non-destructive permeance methods. The first (“method I”) was based solely on the dusty gas model (DGM) for mass-transfer. Thereafter, an expression (“method II”) for the calculation of the cake porosity was derived for Knudsen numbers >10. Permeance analysis revealed pore-sizes (equivalent cylindrical diameter) of the deposited cakes of approximately 200nm, independent of mass deposited (wd=0.7–36.8mg). Calculation of the porosity by method I was prone to large errors due to any anisotropy of the porosity and resulted in unrealistically high εc values at low deposited mass (e.g. εc=0.99 at wd=0.7mg). In contrast, the porosities (average εc=0.947–0.949) calculated by method II were independent of deposited mass and in excellent agreement to scanning electron microscopy (SEM) analysis (εc=0.94–0.97), as well as to previous studies at comparable experimental conditions (εc=0.95).

WE-C-303A-05: Variation in Radiation Doses in Pediatric and Adult Interventional Radiology Procedures: The Need for Dose Optimization

Purpose: To determine the variation in pediatiric and adult doses in cardiac catheterization and angiography procedures and investigate factors that correlate with radiation. Methods and Materials: Effective doses were estimated from the dose area product values of 761 pediatric patients belonging to age groups 0, 1, 5 and 10 years old who underwent coarctation (COA) dilatation, patent ductus arteriosus (PDA) occlusion, pulmonary and diagnostic. The causes for high patient doses were investigated and the correlation of effective dose and DAP with patient weight, equivalent cylindrical diameter, fluoroscopy time and number of cine frames were analyzed. The maximum entance skindoses and effective doses were determined for 114 adult patients for cardiac catheterization and 320 adults for angiography procedures. Techniques to reduce patient entrance doses were investigated. Resuts: Pulmonary and PDA are high dose procedures with an average effective dose of 10 and 8.2 mSv respectively. DAP values showed a good correlation with effective doses for diagnostic and COA dilatation with r2 (p <0.0001) equal to 0.81 and 0.70 respectively. PTCA procedure delivered a maximum skindose (4.5 mGy) that exceeded the threshold dose for skin erythemia. Percutaneous Transhepatic Choleangiography (PTC) and Transjugular Intrahepatic Portosystemic Shunts (TIPSS) delivered the maximum skindose of 983 and 735 mGy. Conclusions: Review of the protocols and setting of image quality criteria for pediatric especially for age groups 0 and 1 and for adult patients in order that flurocospy time, peak kilovoltage and number of cine series be reduced is needed. Pooling all ages, an effective dose conversion coefficient of 120 cGy‐cm2 per mSv can be used for pediatric procedures. This research was supported by IAEA.

Soil quality assessment of an oil-contaminated tropical Alfisol amended with organic wastes using image analysis of pore space

Petroleum products are the most common source of pollution in Nigeria. We studied changes of the pore space of a soil contaminated with petroleum products by image analysis; and also assessed the applicability of fractal scaling of the pore surfaces to estimate soil degradation. The main-plot treatments include control (C), cow dung (CD), poultry manure (PM), and pig waste (PW) each applied at 10 Mg/ha; sub-plot treatments were control (0%), 0.5%, 2.5% and 5% spent oil (SP) applied at 10, 50 and 100 Mg/ha respectively with four replications. The results show that treatment with waste-lubricating oil (spent oil) led to increases in pore space parameters, viz. area, perimeter, count number (hole count), equivalent cylindrical diameter and shape. However, treatment with only organic wastes shows that PM increased these parameters and percent macroporosity over CD and PW. At the 0.5% oil level, the order of this increase was CD > PM > PW while at the 2.5% and 5% oil contamination levels the sequence was PM > PW > CD. This indicates that addition of CD had a greater effect on increasing void space at low oil concentrations, whilst PM was better at high contamination levels. The calculated pore surface dimension ( D s D s) was between 2.30 and 2.80, showing that the pore outlines exhibit fractal behaviour. Oil contaminated soil supplemented with organic wastes showed that the D s followed 0.5%SP > 2.5%SP > 5%SP, indicating increases in irregularity of the soil pores with decrease in oil concentrations. This study demonstrates the applicability of fractal scaling for evaluating pore space of soils amended with cow dung, poultry manure, and pig waste.

Variation in radiation doses in paediatric cardiac catheterisation procedures

Paediatric cardiac catheterisation involves diagnostic and therapeutic procedures that range from simple to complex and can subject paediatric patients to varying radiation doses. The study aims to determine the variation in entrance doses in patients in terms of dose-area product (DAP) values and to investigate the methods for optimising radiation protection. A total of 190 paediatric patients belonging to age groups 0, 1, 5 and 10 y who underwent diagnostic and six selected therapeutic procedures at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia were included in the study. Therapeutic procedures include coarctation (COA), patent ductus arteriosus (PDA), radiofrequency ablation, pulmonary, embolisation and septostomy. Fluoroscopy and cine radiography were used in all procedures. Patient demography (weight, age, gender and height), radiographic technique factors, fluoroscopy and cine time, frame rate, and DAP values were taken from patients records. Effective doses for each procedure were estimated from the DAP values. The mean DAP per procedure were analysed for correlation with patient equivalent cylindrical diameter, weight, fluoroscopy time and number of frames. Factors influencing the variation in doses were investigated. Initial results show that PDA occlusion has the highest mean DAP value of 23.21 Gy-cm2, while the diagnostic and septostomy procedures have the lowest value of 7.77 and 6.95 Gy-cm2, respectively.

A review of non‐equilibrium water flow and solute transport in soil macropores: principles, controlling factors and consequences for water quality

SummaryThis review discusses the causes and consequences of ‘non‐equilibrium’ water flow and solute transport in large structural pores or macropores (root and earthworm channels, fissures and interaggregate voids). The experimental evidence suggests that pores larger thanc. 0.3 mm in equivalent cylindrical diameter allow rapid non‐equilibrium flow. Apart from their large size and continuity, this is also due to the presence of impermeable linings and coatings that restrict lateral mass exchange. Macropores also represent microsites in soil that are more biologically active, and often more chemically reactive than the bulk soil. However, sorption retardation during transport through such pores is weaker than in the bulk soil, due to their small surface areas and significant kinetic effects, especially in larger macropores. The potential for non‐equilibrium water flow and solute transport at any site depends on the nature of the macropore network, which is determined by the factors of structure formation and degradation, including the abundance and activity of soil biota such as earthworms, soil properties (e.g. clay content), site factors (e.g. slope position, drying intensity, vegetation) and management (e.g. cropping, tillage, traffic). A conceptual model is proposed that summarizes these effects of site factors on the inherent potential for non‐equilibrium water flow and solute transport in macropores. Initial and boundary conditions determine the extent to which this potential is realized. High rain intensities clearly increase the strength of non‐equilibrium flow in macropores, but the effects of initial water content seem complex, due to the confounding effects of soil shrinkage and water repellency. The impacts of macropore flow on water quality are most significant for relatively immobile solutes that are foreign to the soil and whose effects on ecosystem and human health are pronounced even at small leached fractions (e.g. pesticides). The review concludes with a discussion of topics where process understanding is still lacking, and also suggests some potential applications of the considerable knowledge that has accumulated in recent decades.

Characterising the packing and dead-end filter cake compressibility of the polymorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415

Suspensions of the polymorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415 were grown in batch and continuous culture, producing broths with a range of mean cell morphologies. The mean cell aspect ratio, L dm, defined as the mean ratio of total cell length to equivalent cylindrical diameter, was measured for each broth by image analysis and ranged from 1.7 to 51. The porosity of the cell pellet formed in a bench-top centrifuge was measured for each broth and in all cases, the pellet porosity decreased linearly with increasing centrifuge speed. This decrease became more pronounced as L dm increased. The extrapolated zero-speed pellet porosity, ε 0, was correlated with L dm by the expression ε 0=1−1/(1.24+0.062 L dm). The dead-end specific cake resistance, α, was measured for each broth in the pressure range 30–180 kPa. The cake compressibility constant, k c, defined by the expression α=α 0(1+k c ΔP) was found to increase with increasing values of L dm. The increase was most rapid in the region, L dm<10. Microscopic observations indicate that cell deformation at branching points may contribute to cake compressibility.

CHARACTERIZATION OF MACROPORE MORPHOLOGY IN A SANDY LOAM SOIL USING X-RAY COMPUTER ASSISTED TOMOGRAPHY AND GEOSTATISTICAL ANALYSIS

Our understanding of the factors affecting the leaching of chemicals such as pesticides and fertilizers into soils is limited, due in part to a lack of adequate non-destructive measurements of soil pore size distribution. The recent application of X-Ray Computer Assisted Tomography scanning to non-medical fields such as soil physics has allowed the development of a new and non-destructive technique with considerable potential for quantification of soil and water processes. The present study was undertaken to develop an innovative protocol for the characterization and visualization of soil macropores. It focuses primarily on the characterization of macropore morphology in large undisturbed soil columns using a 4th generation X-ray CAT scanner. The objective of the study is to assess, in quantitative terms, variations in the morphology of macropores as a function of depth. In order to evaluate these variations, the number of macropores, soil macroporosity, macropore size, hydraulic radius, and circularity have been computed and are presented in the paper. Aspects of geostatistics, which have been used to describe the spatial distribution and spatial continuity of soil macroporosity are also presented. Pores larger or equal to 1.0 mm in equivalent diameter were readily detected. It was found that the average macroporosity of the four soil columns fluctuated between 2.1 and 3.8%. Macroporosity was found to decrease significantly with depth. Similarly, the number of macropores decreased by 0.7% to 2.5% over the entire depth of the soil columns. It was also found that the macropore-size distributions exhibited a peak for all soil columns and at all depths for macropores having an equivalent cylindrical diameter ranging from 2–4 mm. The number of macropores in this category decreased with depth. From the hydraulic radius distribution, it was inferred that about 20% of macropore throats have a diameter of 1.6 mm. Moreover, it was noted that the relative percentage of circular macropores increased with depth. Semi-variograms showed spatial dependency for most soil sections up to 22 pixels (17 mm).

Effect of Cell Morphology on Dead‐End Filtration of the Dimorphic Yeast Kluyveromycesmarxianus Var. marxianus NRRLy2415

The dead-end filtration characteristics of the dimorphic yeast Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415 were investigated for a range of mean cell morphologies, ranging from predominantly yeast-like to predominantly filamentous. Semiautomated image analysis was used to measure the mean cell specific surface area, Sv, and the mean ratio of cell length to equivalent cylindrical diameter, Ldm, in each broth. The method of Ju and Ho (Biotechnol. Bioeng. 1988, 32, 95-99) was used to show that for broths with Ldm values between 1.72 and 10.03, the voidage of cell pellets formed by centrifugation increased with increasing Ldm. In the pressure range 30-180 kPa, the specific filter cake resistance, alpha, was found to be related to pressure, DeltaP, through the equation alpha = alpha0(1 + kcDeltaP). The dependence of alpha0/Sv2 on Ldm was found to be qualitatively consistent with the pellet voidage data and the Carman-Kozeny equation. Considerably better agreement with the experimental data was obtained when the Kozeny constant, K, was treated as variable and related to Ldm through the equation K = 4.83 + 7.08 log10 Ldm. The cake compressibility constant, kc, was found to increase with increasing Ldm, a phenomenon consistent with the wide range of voidages that can be displayed by beds of long cylinders.

Reference Man in Diagnostic Radiology Dosimetry

Patient size and shape are considered in patient dose evaluations in diagnostic radiology. The size, shape and constitution of the patients are shown to relate exponentially to the energy imparted during examination of the trunk. The equivalent cylindrical diameter of the patients body is used as the independent variable. Exponential functions are created by linear regression. A method is suggested by which co-ordinate transformations reduce data to a base line defined by Reference Man. It is shown that the method reduces the range of energy imparted during X ray examinations of the trunk. Resulting data constitute a finer instrument for intercomparisons between hospitals for the same examination. Reference Man, stripped of 10 kg subcutaneous adipose tissue, is used as the non-fat standard. The suggested method is used to estimate the fraction of energy imparted to vital organs only.

Reference Man in Diagnostic Radiology Dosimetry

Patient size and shape are considered in patient dose evaluations in diagnostic radiology. The size, shape and constitution of the patients are shown to relate exponentially to the energy imparted during examination of the trunk. The equivalent cylindrical diameter of the patients body is used as the independent variable. Exponential functions are created by linear regression. A method is suggested by which co-ordinate transformations reduce data to a base line defined by Reference Man. It is shown that the method reduces the range of energy imparted during X ray examinations of the trunk. Resulting data constitute a finer instrument for intercomparisons between hospitals for the same examination. Reference Man, stripped of 10 kg subcutaneous adipose tissue, is used as the non-fat standard. The suggested method is used to estimate the fraction of energy imparted to vital organs only.

The effects of different management practices on the physical properties of a sandy loam soil in Southern Nigeria

The effects of different management practices on the physical properties of a sandy loam soil in Southern Nigeria were studied for two cropping seasons. The bulk densities of the top 0–10-cm soil depths were significantly reduced in plots under 13 years of Panicum maximum and Centrosema pubescens covers. Pores of equivalent cylindrical diameter > 0.05 mm were increased significantly under the two covers. Up to 33% of the saturation water content was released between tensions of 0 and 0.06 bar in the sandy loam soil of all the treatment plots. Furthermore an average of 24% of this water was released between tensions of 0.06 and 0.33 bar. Infiltration rates, measured at the end of the growing season, ranged from 240 mm h −1 under the bare fallow treatment to 1326 mm h −1 under the Centrosema cover. There was no significant difference between the tilled and no-tillage plots. Saturated hydraulic conductivities were significantly higher under the Panicum and Centrosema covers. The effect of tillage on conductivity was not appreciable. The highest weekly 5-cm depth, 1.30 p.m. soil temperature (32°C) was obtained under the bare fallow treatment and the lowest (23.5°) under the Panicum cover. Tillage had no significant effect on the soil temperature. Thirteen years of continuous Centrosema and Panicum covers had a significant effect on the physical properties of the tropical sandy loam soil. Tillage effects were not significant after 2 years of cropping.

Soil damage by intensive arable cultivation: temporary or permanent?

Intensive arable production normally involves an increasing frequency of cultivation, and hence an increasing probability of soil compaction, particularly if the soil is cultivated when it is wet. The effects on the potential ability of the soil to produce crops is uncertain, because the relations between soil physical conditions and crop growth are poorly understood. To measure damage requires improved techniques for measuring pore size distribution, as well as pore continuity and stability. Most damage takes the form of a reduction in the number of transmission pores (those greater than 0.05 mm, equivalent cylindrical diameter) although storage pores may also be lost in intensively cultivated soils. Where damage is primarily in the surface soil it can usually be repaired by appropriate cultivations. Where compaction of subsurface soil occurs, or blockage of subsurface pores by dispersion of clay from disrupted aggregates, the damage is less easily repaired. Soils differ considerably in their ability to withstand intensive cultivation. The behaviour of soil aggregates on immersion in water provides a useful guide to those likely to suffer more permanent damage, and those where increasingly intensive production can be safely practised.