Retention Function Research Articles

Approximation of van Genuchten Parameter Ranges from Hydraulic Conductivity Data.

The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem-van Genuchten model which requires the shape parameters and . These, however, are difficult to obtain. When data is scarce, and are often taken from literature and may deviate largely from actual values. The current study presents a novel mathematical model for the approximation of and and for the further estimation of realistic value ranges, which may be used as parameter space, for example, for the calibration of a numerical model. The model was developed for cases where data is scarce and only values of saturated hydraulic conductivity are available. It is based on a large data set from literature and it is demonstrated that the model estimates mean values from that data set with a good accuracy. In order to show the applicability of the model, a second data set has been compiled anew (provided as Supporting Information). The model is incorporated into the current version of the freeware computer program HYPAGS, which enables easy usage.

Copper retention influenced by an invasive and a native plant in riparian soil

Riparian soils are exposed to diverse anthropogenic stressors via aquatic pathways. Our study focuses on the impact of the invasive plant Impatiens glandulifera (Himalayan Balm) on processes that affect the filter and retention function of soils for copper, a regionally applied fungicide.Two soils, overgrown with the invasive I. glandulifera and by the native Urtica dioica were characterized for general soil properties and their copper retention ability assessed by a sequential extraction after seven days flooding with three different copper concentrations.We observed higher values for the absolute copper concentration in all fractions for the soil overgrown with I. glandulifera than for the soil overgrown with U. dioica. However, with respect to the total content, copper was more mobile in soil overgrown with U. dioica despite a higher organic matter content. The lower extraction recovery of the U. dioica soil suggests that more copper was mobilized in colloids which in long-term are easier washed out while I. glandulifera favors immobilization of organically chelated copper enhancing a legacy effect.Our results highlight the plant specific impact possibly induced by root exudates and plant residues affecting soil organic matter quality including the colloidal fraction and thus filter and retention functions of riparian soils.

On evaluating the hypothesis of shape similarity between soil particle-size distribution and water retention function

Two pedotransfer functions (PTFs) are available in the literature enabling the soil water retention function (WRF) to be estimated from knowledge of the soil particle-size distribution (PSD), oven-dry soil bulk density (b), and saturated soil water content (s): i) the Arya and Heitman model (PTF-AH) and ii) the Mohammadi and Vanclooster model (PTF-MV). These physico-empirical PTFs rely on the hypothesis of shape similarity between PSD and WRF, and do not require the calibration of the input parameters. In the first stage, twenty-seven PSD models were evaluated using 4,128 soil samples collected in Campania (southern Italy). These models were ranked according to the root mean square residuals (RMSR), corrected Akaike Information Criterion (AICc), and adjusted coefficient of determination (R2adj). In the second stage, three subsets of PSD and WRF data (DS-1, DS-2, and DS-3), comprising 282 soil samples, were used to evaluate the two PTFs using the best three PSD models selected in the first stage. The hypothesis of shape similarity was assumed as acceptable only when the RMSR value was lower than the field standard deviation of the WRFs (*), which is viewed as a tolerance threshold and computed from the physically-based scaling approach proposed by Kosugi and Hopmans (1998). In the first study area (DS-1), characterized by a fairly uniform, loamy textured volcanic soil, the PTF-AH outperformed the PTF-MV and both PTFs provided reasonable performance within the acceptance threshold (i.e., RMSR < *). In the other two heterogeneous field sites (DS-2 and DS-3, characterized by soil textural classes that span from clay and clay-loam to loam and even sandy-loam soils), the PTF-MV (with 3% to 6% RMSR surpassing *) outperformed the PTF-AH (with 8% to 30% RMSR surpassing *) and the majority of RMSR values were larger than those obtained in the original studies. The mean relative error (MRE) revealed that the PTF-MV systematically underestimates the measured WRFs, whereas the PTF-AH provided negative MRE values indicating an overall overestimation. The outcomes of our study provide a critical evaluation when using calibration-free PTFs to predict WRFs over large areas.

Particle detachment in reservoir flows by breakage due to induced stresses and drag

Suspension-colloidal-nano transport in porous media encompasses the detachment of detrital fines against electrostatic attraction and authigenic fines by breakage, from the rock surface. While much is currently known about the underlying mechanisms governing detachment of detrital particles, including detachment criteria at the pore scale and its upscaling for the core scale, a critical gap exists due to absence of this knowledge for authigenic fines. For the first time, we integrate the 3D version of Timoshenko's beam theory of elastic cylinder deformation with a CFD-based model for viscous flow around the attached particle and with strength failure criteria for particle-rock bond. This results in a novel explicit criterium for fines detachment by breakage at the pore scale. The criterium includes analytical expressions for tensile and shear stress maxima along with two geometric diagrams which allow determining the breaking stress. This leads to an explicit formula for the flow velocity that provides the particle-rock bond breakage. Its upscaling yields a novel mathematical model for fines detachment by breakage, expressed in the form of the maximum retained concentration of attached fines versus flow velocity – maximum retention function (MRF) for breakage. We performed corefloods with piecewise constant increasing flow rates, measuring breakthrough concentration and pressure drop across the core. It was found out that the behaviour of the measured data is consistent with two-population colloidal transport, attributed to detrital and authigenic fines migration. Indeed, the laboratory data show high match with the analytical model for two-population colloidal transport, which validates the proposed mathematical model for fines detachment by breakage.

Climate Warming Dominates Vegetation Productivity in the Hanjiang River Basin, China

The Hanjiang River Basin (HJRB) encompasses the Danjiangkou Reservoir, a critical water source for the South-to-North Water Transfer project, the world’s largest such endeavor. Recent studies have highlighted that increased vegetation growth in the HJRB has led to reduced water availability in the region. To investigate the seasonal dynamics and spatial patterns of vegetation and their association with the local climate, we employed Gross Primary Productivity (GPP), a pivotal component of terrestrial carbon-water cycling, derived from the MODIS MOD17A2HGF dataset at a 500 m resolution. We combined this dataset with station meteorological data and the Standardized Precipitation Evapotranspiration Index (SPEI) to explore the complex relationship between vegetation productivity, climate fluctuations, and hydrothermal changes in the HJRB from 2000 to 2020. Our findings reveal that the rising trend in vegetation productivity in the HJRB is primarily attributable to climate warming. Different types of vegetation in the upstream and downstream areas exhibit varying water requirements. While the region has not experienced prolonged widespread drought conditions thanks to its excellent water conservation capabilities, there remains a certain level of drought risk in the downstream area as the climate continues to warm. Moreover, variables such as wind speed and sunshine duration significantly impact the hydrothermal conditions within the river basin, consequently influencing vegetation productivity. This study elucidates the mechanisms through which climate change affects vegetation productivity in the HJRB. Despite afforestation efforts in the upstream region and climate warming leading to increased greening, there may be implications for the water retention function of the HJRB. This understanding is crucial for water resource management and ecosystem sustainability in the HJRB.

B - 05 Intervention Resistant Dyslexia: a Neuropsychological Profile.

Dyslexia is a brain based neurodevelopmental disorder marked by deficits in phonemic awareness and fluency. Brain structures implicated include the left superior temporal gyrus, planum temporal, and frontal regions. Convergent research supports the efficacy of multisensory, systematic, hierarchically organized, phonics-based instruction This study examines a bright, severely dyslexic youngster who, despite seven years of intensive intervention, has made little appreciable progress. Co-morbid neuropsychological weaknesses are implicated in his failure to respond to intervention. The subject is a 13-year-old, 8th grade boy who presented for neuropsychological evaluation subsequent to a history of dyslexia. He attends a specialized school employing evidence-based reading interventions in a small classroom. Despite intellectual functions in the high average range and seven years of consistent intervention, he continues to read at a first to second grade level. Findings from a comprehensive neuropsychological assessment revealed a complex profile characteristic of dyslexia with multiple unexpected deficits in several neurocognitive processes. Data revealed weaknesses in processing speed, verbal working memory, retention, and executive functions. There is little empirical research examining response to intervention in severely dyslexic children. In this case study, the cumulative impact of underlying cognitive weaknesses in speed, working memory, verbal retention, and executive functions are thought to have negatively impacted progress. This youngster is among a small population of individuals with severe dyslexia who do not respond well to intervention. There is a need for awareness of such youngsters and both neuropsychological assessment and research to determine the impact of co-occurring neurocognitive deficits contributing to poor progress.

Staff Retention and Organizational Performance in Kasese District in Western Uganda

The pragmatic study evaluated the association between Staff Retention and Organizational performance in Kasese District in Western Uganda. The inquiry study utilized a cross sectional survey research design with quantitative and qualitative mockups. A sample of 148 participants were carefully chosen from 240 individuals using a table developed by Morgan & Kreijcie (1970). Information was assembled by means of questionnaires and interview schedules. Data was appraised using frequencies, percentages, Pearson linear correlation coefficient (PLCC) for quantitative measurements and thematic analysis was engaged for organizing qualitative proof. The study verdicts came up with a significant relationship between Staff retention and Organizational Performance in Kasese District in Western Uganda. The project team concluded that Staff Retention is vital for increasing the productivity of an organization especially in local governments because it conventions with issues to do with stability of tenure of office. If the employees are well retained in an organization, they can be a source of motivation for socio-economic development of local governments at large. From the research project results, the academics recommended that Staff Retention in Kasese district sub-national government in Uganda should continuously put in place better conditions of work such as descent accommodation, free medical care, payment of overtime allowances and giving scholarships for those who want go for further studies. This can be done through putting in place operational committees to make sure that government policies on staff retention are well cherished and implemented. The government of Uganda should increase on the budget meant to facilitate staff retention function in Human Resource Department so that a big number of local government employees can be retained for effective service delivery in Kasese District local government.

Understanding the balance between soil conservation and soil water storage capacity during the process of vegetation restoration in semi‐arid watersheds in the Loess Plateau, China

AbstractIn the Loess Plateau, gaining insights into the water storage and soil retention functions of diverse vegetation types, especially, in the semi‐arid watersheds is crucial for identifying the key factors necessary to ensure sustainable development and achieve land degradation neutrality. In this study, five different land use types such as forest, shrub, artificial grass, and natural grasslands were surveyed from 2014 to 2020. Meanwhile, bare land was also used as a control plot. The trade‐off between erosion mitigation and water consumption indicator was quantified based on the ecosystem services perspective benefits. Our results showed that there are significant differences among different land use types (p < 0.05): natural grassland > shrubs > artificial grassland > forests. Vegetation restoration was able to change the soil particle size distribution, increasing clay and silt content, and decreasing sand particles. During the growing season, surface soil water storage decreased in all land use types coinciding with the higher decrease in the control plot. The change in surface water storage in the forest was the most stable, with a decrease of 0.13 mm. The trade‐off between erosion mitigation and water consumption indicator was less than 0 for all vegetation types, which indicates a synergistic effect on soil conservation and water storage benefit. Our results demonstrated that shrubs can register the most balanced benefit of water storage and soil preservation. This is a solid basis for the selection of specific vegetation types and the optimization of the watershed landscape in the middle reaches of the Yellow River, characterized by vulnerable areas due to aridification.

Improved calculation of soil hydraulic conductivity with the simplified evaporation method

AbstractNumerical modeling of soil water dynamics and storage is generally based on the Richards equation. Its solution requires knowledge of the soil hydraulic properties (SHP): the soil water retention function and the hydraulic conductivity function. To determine SHP, laboratory evaporation experiments are particularly popular because they provide data for both SHP functions. The evaluation by the simplified evaporation method (SEM) method, originally proposed by Schindler and subsequently improved by several authors, relies on linearization assumptions that allow for a relatively simple calculation scheme but result in biased conductivity data for some soils. The objective of this study is to propose and test an improved computational scheme for the hydraulic conductivity function. We present the new theory and show that it leads generally to higher accuracy of the conductivity function. The improvement is most pronounced for sandy soils and soil water pressure heads below −100 cm, where the original method provided data with bias.

Integrative modeling of lncRNA-chromatin interaction maps reveals diverse mechanisms of nuclear retention

BackgroundMany long non-coding RNAs, known to be involved in transcriptional regulation, are enriched in the nucleus and interact with chromatin. However, their mechanisms of chromatin interaction and the served cellular functions are poorly understood. We sought to characterize the mechanisms of lncRNA nuclear retention by systematically mapping the sequence and chromatin features that distinguish lncRNA-interacting genomic segments.ResultsWe found DNA 5-mer frequencies to be predictive of chromatin interactions for all lncRNAs, suggesting sequence-specificity as a global theme in the interactome. Sequence features representing protein-DNA and protein-RNA binding motifs revealed potential mechanisms for specific lncRNAs. Complementary to these global themes, transcription-related features and DNA-RNA triplex formation potential were noted to be highly predictive for two mutually exclusive sets of lncRNAs. DNA methylation was also noted to be a significant predictor, but only when combined with other epigenomic features.ConclusionsTaken together, our statistical findings suggest that a group of lncRNAs interacts with transcriptionally inactive chromatin through triplex formation, whereas another group interacts with transcriptionally active regions and is involved in DNA Damage Response (DDR) through formation of R-loops. Curiously, we observed a strong pattern of enrichment of 5-mers in four potentially interacting entities: lncRNA-bound DNA tiles, lncRNAs, miRNA seed sequences, and repeat elements. This finding points to a broad sequence-based network of interactions that may underlie regulation of fundamental cellular functions. Overall, this study reveals diverse sequence and chromatin features related to lncRNA-chromatin interactions, suggesting potential mechanisms of nuclear retention and regulatory function.

Integrated Ecological Risk Assessment of the Agricultural Area under a High Anthropopressure Based on Chemical, Ecotoxicological and Ecological Indicators

Agricultural land is often located close to highly urbanised/industrialised areas and is subject to continuous anthropogenic pressure associated with the emission of many pollutants, ultimately deposited in the soil. Most studies on ecological risk assessment have only analysed the total contaminants’ concentration, which does not reflect their bioavailability or toxicity and often leads to an overestimation of risk. Therefore, in our study, we used an interdisciplinary approach, whereby the final conclusions about the risk in a given area are based on the integration of detailed data from chemical, ecotoxicological and ecological analysis. The research was carried out on agricultural land exposed to high levels of anthropopression for more than 100 years. Chemical measurements comprised both the total and bioavailable PAH content. A battery of bio-assays describing effects on soil retention and habitat function was used for ecotoxicity testing, and ecological indicators included enzymatic activity, respiration, microbial biomass, carbon mineralisation and nitrification. The integrated IntRisk index ranged from 0.19 to 0.94, and this was mainly due to high values of the chemical risk index, while the ecotoxicological and ecological results indicated no or low risk. The majority of the area (almost 90%) had acceptable risk levels, no/low risk (IntRisk < 0.5) at 57% of the sites and medium risk at 28% of the area. Very high unacceptable risk (IntRisk 0.77–0.94) was only at three sampling sites. The integration of data from a set of 15 indicators allowed us to derive quantitative risk indexes and delineate the limited area which needs additional action.

Assessment of the interactions between soil–biosphere–atmosphere (ISBA) land surface model soil hydrology, using four closed-form soil water relationships and several lysimeters

Abstract. Soil water drainage is the main source of groundwater recharge and river flow. It is therefore a key process for water resource management. In this study, we evaluate the soil hydrology and the soil water drainage, simulated by the interactions between soil–biosphere–atmosphere (ISBA) land surface model currently used for hydrological applications from the watershed scale to the global scale, where parameters are generally not calibrated. This evaluation is done using seven lysimeters from two long-term model approach sites measuring hourly water dynamics between 2009 and 2019 in northeastern France. These 2 m depth lysimeters are filled with different soil types and are either maintained as bare soil or covered with vegetation. Four closed-form equations describing soil water retention and hydraulic conductivity functions are tested, namely the commonly used equations from Brooks and Corey (1966) and van Genuchten (1980), a combination of the van Genuchten (1980) soil water retention function with the Brooks and Corey (1966) unsaturated hydraulic conductivity function, and, for the very first time in a land surface model (LSM), a modified version of the van Genuchten (1980) equations, with a new hydraulic conductivity curve proposed by Iden et al. (2015). The results indicate good performance by ISBA with the different closure equations in terms of soil volumetric water content and water mass. The drained flow at the bottom of the lysimeter is well simulated, using Brooks and Corey (1966), while some weaknesses appear with van Genuchten (1980) due to the abrupt shape near the saturation of its hydraulic conductivity function. The mixed form or the new van Genuchten (1980) hydraulic conductivity function from Iden et al. (2015) allows the solving of this problem and even improves the simulation of the drainage dynamic, especially for intense drainage events. The study also highlights the importance of the vertical heterogeneity of the soil hydrodynamic parameters to correctly simulate the drainage dynamic, in addition to the primary influence of the parameters characterizing the shape of the soil water retention function.

Feasibility of virtual Alzheimer's biomarker disclosure: Findings from an observational cohort.

Increased availability of Alzheimer's disease (AD) biomarker tests provides older adults with opportunities to seek out and learn results. We evaluated the feasibility of virtually returning AD biomarker results. Trained study clinicians disclosed amyloid positron emission tomography (PET) results and provided dementia risk-reduction counseling via televideo to cognitively unimpaired participants already enrolled in AD research (n = 99; mean age ± SD: 72.0 ± 4.8; 67% women; 95% White; 28% amyloid elevated). Our study demonstrated acceptable levels of retention (93%), compliance (98%), adherence (98%), clinician competence (97%), education comprehension (quiz scores 14/15), and virtual visit functionality (rating 9.4/10). Depression, anxiety, and suicidality remained low and did not differ by amyloid result. Virtual return of amyloid PET results to cognitively unimpaired research participants is feasible and does not result in increased psychological symptoms. Technological barriers for some participants highlight the need for flexibility. These findings support the use of televideo in AD biomarker disclosure, although our study sample and design have important limitations for generalizability.

Exploring an Integrated System for Urban Stormwater Management: A Systematic Literature Review of Solutions at Building and District Scales

Climate change has aggravated the frequency and severity of extreme weather events, particularly in flood-related hazards. Cities nowadays face significant challenges in stormwater management from frequent heavy rainfalls. Traditional urban drainage systems can no longer cope with large amounts of surface runoff; cities are searching for new ways to deal with urban stormwater. Green roofs and other nature-based solutions have been widely used for stormwater management by combining water purification and retention functions but have not yet fully solved the flood problems. This article aims to (1) explore the different aspects of urban water management, particularly the urban stormwater topic, and (2) identify the existing solutions and discuss the potential and barriers to integrated solutions implementation. By introducing the concept of four domains and finding the overlapping area to investigate, we analyzed different solutions to reduce rainwater runoff from the roof and ground level, aiming at building and district scales. This paper proves that further research direction could constitute an integrated system to work together for urban stormwater management.

Effects of different inferior mesenteric artery ligation levels on the prognosis of patients with low rectal cancer.

Regarding low rectal cancer (RC) low anterior resection (LAR), a specific consensus regarding the optimal level of inferior mesenteric artery (IMA) ligation does not exist. To systematically evaluate the effects of different IMA ligation methods on the prognosis of patients with low RC, so as to further guide clinical treatment. Between January 2013 and December 2018, 158 patients with low RC underwent LAR. According to the IMA ligation method used, the cases were divided into the low-ligation group (LL group; n = 66) and the high-ligation group (HL group; n = 92). The basic information, operation indicators, postoperative data, and long-term survival in the 2 groups were compared. Sixty cases in the HL group and 60 cases in the LL group were successfully matched using propensity score matching (PSM). There were no statistically significant differences in intraoperative bleeding, intraoperative time, postoperative hospital stay, harvested lymph nodes (LNs), postoperative complications (including urinary retention, urinary incontinence, anastomotic leaks, bowel obstruction, incisional infection, and anal function 3 months after surgery), overall survival (OS), disease-free survival (DFS), local recurrence, and distant metastasis between the 2 groups (p > 0.05). Compared with the HL group, the time to first flatus and the time to fluid intake were shorter in the LL group (p < 0.05). In general, the different IMA ligation methods have no significantly different effects on the prognosis of patients with low RC, but the LL group showed restored intestinal motility earlier.

Variability of in situ soil water retention curves under different tillage systems and growing seasons

Soil pore space can change over time due to tillage, frost, wetting and drying cycles, plant roots, and compaction. However, a soil water retention curve (SWRC) is usually considered to be static and is determinedin a laboratory on a limited number of small soil samples. Field SWRCs were determined at a depth of 20 cm on Mollic Gleysol. Measurements were made in two growing seasons at different spatial locations on plots with different tillage systems: no-tillage (NT) and conventional tillage (CT). The unimodal van Genuchten retention function (VG) was fitted to each SWRC and model parameters were estimated. We evaluated the variability of the curves within growing seasons, predicted soilwater contents at field capacity, and evaluated the differences in the estimated parameters of the VG model between different growing seasons and tillage systems considering intraseasonal and spatial variability. The shape of the curves depended more on the environmental conditions during the growing season than on the tillage system. In the wetter and cooler growing season of 2020, when soybeans were grown, the soil retained water in a narrower range. In the drier growing season of 2021, when maize was grown, intraseasonal variability in SWRCs was greater than in 2020. Regardless of the growing season, estimated α values were more intraseasonally variable under the CT than under the NT. Based on the SWRCs, predicted water contents at field capacity varied intraseasonally, seasonally, and spatially. Accounting for spatial and intraseasonal variability, the estimated VG parameter θr differed between years, regardless of tillage system. In 2020, the parameter α was higher under the NT system than under the CT system. Under the CT, α differed between years, while under NT it did not. For the parameter n, there were no significant differences between tillage systems or growing seasons. Seasonal, intraseasonal, and spatial variability in soil hydraulic properties should be considered in soil water modelling studies.

Predicting microplastic masses in river networks with high spatial resolution at country level

Microplastics are a ubiquitous contaminant of natural waters, and a lot of field monitoring is currently performed. However, what is missing so far is a general understanding how emissions of microplastics are linked to environmental exposure, especially on larger geographic scales such as countries. Here we coupled a high-resolution microplastic release model with a fate model in rivers and lakes and parameterized it for Switzerland on a country scale to predict masses of microplastics in each river section for seven different polymers. The results show that catchment characteristics, for example, distribution of releases within the catchment, location and size of lakes or river connections, are as important as polymer properties such as density. There is no simple linear function of microplastic retention within a catchment in dependency of river length to the outlet. Instead, we found that different catchments cover a wide range of retained fractions for microplastics. Consequently, we argue that the availability and use of spatially distributed release data and performing modelling on high spatial resolution is of importance when estimating concentrations of microplastics in large areas such as countries.

Agricultural Residues as Potential Diluents in Natural Rubber Formulation

Agricultural residues such as Maize Husk, Groundnut Shell, Coconut Shell and Sugarcane Bagasse were collected, sorted, dried and ground to particulate fillers. The various fillers were characterized in terms of density, moisture content and pH value. Single ordinates of 150 µm particle size and 30 parts per hundred of rubber (pphr) loading were respectively adopted for all filler types. They were used alongside with conventional Sulphur vulcanization system (high Sulphur to low organo-accelerator level) in the formulations of natural rubber compounds. Tests such as tensile strength at 400% elongation, constant force compression set, abrasion resistance as a function of percentage mass retention on surface exposure to a rotating abrasive surface and thermal stability using differential scanning calorimeter were carried out. Results obtained revealed that rubber vulcanizate samples filled with coconut shell and sugarcane bagasse had hardness values of 58 and 57 on Shore A scale while unfilled vulcanizate and carbon black filled sample had respective values of 45 and 49 Shore A hardness. However, unfilled vulcanizate and carbon black filled vulcanizate showed superior values of tensile strength at 400% elongation to the ones filled with agricultural residues. Therefore, these agricultural residues can serve as diluents in the formulation of rubber vulcanizates.

Fines migration during coal bed methane production: mathematical and laboratory modelling, field cases

Fines migration in coalbed methane (CBM) fields comprises a serious environmental and gas-production challenge. The literature widely reports two kinds of fines: potential coal fines, which are a part of the coal body and can be detached by breakage under a significant drag force exerted from the inflowing water, and detrital coal fines, which are attached to the coal body by electrostatic forces. The theory for detrital coal fines migration is well developed. A theory for potential coal fines, where the drag deforms the coal asperities and detaches fines by rock failure, is not available. The objectives of this study are (1) to derive the governing equations for fines generation by breakage using failure criteria, and (2) to predict well productivity during dewatering and gas production using laboratory-based modelling. The micro-model developed is based on beam theory and comprises static rock deformation by the flow-through water and calculating failure criteria by tensile and shear stresses. The failure condition determines the number of fines that detach after the application of each flow rate, allowing determining the maximum retention function of potential coal fines. The breakage micro-model is incorporated into filtration equations that account for fines mobilisation, migration, straining and consequent permeability decline. Eight series of lab flooding data with coal cores have been treated. The close match between the lab and model validates the model developed. The model allows predicting productivity decline due to permeability reduction by fines breakage and straining.

Contact restriction time after common nuclear medicine therapies: spreadsheet implementation based on conservative retention function and individual measurements

The increasing use of new radiopharmaceuticals invites us to reconsider some radiation protection issues, such as the contact restriction time that limits public exposure by nuclear medicine patients. Contact restriction time should be patient specific and conservative, and its assessment made easy for clinicians. Here a method is proposed based on conservative estimation of the whole-body retention function and at least one measurement of the patient’s dose rate. Recommended values of the retention function are given for eight therapies: 131I (Graves’ disease, remnant ablation, patient follow-up, meta-iodobenzylguanidine), 177Lu-prostate-specific membrane antigen and 177Lu-DOTATATE therapies, and 90Y and 166Ho microsphere injection of the liver. The patient line source model for scaling dose rate from one distance to another is included in the restriction time calculation. The method is benchmarked against published values and the influence of the dose rate scaling and whole-body retention function illustrated. A spreadsheet is provided, along with the source code, with recommended values for the eight therapies. The recommended values can be changed as well as the dose rate scaling function, and other radiopharmaceuticals can be included in the spreadsheet provided retention functions are defined.