Estimation Of Surface Area Research Articles

Above- and below-ground allocation and functional trait response to soil water inputs and drying rates of two common savanna grasses

The study of functional trait plasticity and optimal allocation strategies in a water competition context may help to explain the mechanisms relating plant competition to ecological semi-arid patterns. We measured four functional plant traits –root to shoot ratio, superficial to deep roots ratio, root diameter, and root estimated surface area to shoot ratio– in wild populations of two C4 grasses in a Kenyan savanna to assess their responses to different water inputs (changing with latitude) and soil drying rates (driven by canopy cover). Root:shoot allocation was different between the two species. We show that to account for root architecture helps understanding root allocation strategies, especially in species with high plasticity in root geometry. Concretely, in our case, a higher root allocation in wetter conditions was driven by water storage and not water foraging in the species with high root diameter variability. Superficial root allocation responded to changes associated with drying rates but not to water input, and shallower root systems developed under higher water stress conditions, supporting rainfall intermittency models of savanna tree-grass competition. We also suggest self-shading as a facilitation mechanism that may affect spatial patterns according to the scale-dependent feedback hypothesis.

Recent Surface Water Extent of Lake Chad from Multispectral Sensors and GRACE.

Consistent observations of lakes and reservoirs that comprise the majority of surface freshwater globally are limited, especially in Africa where water bodies are exposed to unfavorable climatic conditions and human interactions. Publicly available satellite imagery has increased the ability to monitor water bodies of various sizes without much financial hassle. Landsat 7 and 8 images were used in this study to estimate area changes around Lake Chad. The Automated Water Extraction Index (AWEI), Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI) and Normalized Difference Vegetation Index (NDVI) were compared for the remote sensing retrieval process of surface water. Otsu threshold method was used to separate water from non-water features. With an overall accuracy of ~96% and an inter-rater agreement (kappa coefficient) of 0.91, the MNDWI was a better indicator for mapping recent area changes in Lake Chad and was used to estimate the lake’s area changes from 2003–2016. Extracted monthly areas showed an increasing trend and ranged between ~1242 km2 and 2231 km2 indicating high variability within the 13-year period, 2003–2016. In addition, we combined Landsat measurements with Total Water Storage Anomaly (TWSA) data from the Gravity Recovery and Climate Experiment (GRACE) satellites. This combination is well matched with our estimated surface area trends. This work not only demonstrates the importance of remote sensing in sparsely gauged developing countries, it also suggests the use of freely available high-quality imagery data to address existing lake crisis.

Application of Population Balance Theory for Dynamic Modeling of Methane and Ethane Hydrate Formation Processes

Natural gas hydrates are considered as a promising fuel source in the relatively near future. Kinetic modeling of various steps of the natural gas hydrate formation process, such as dissolution, nucleation, and growth processes, has received numerous attentions. A novel mechanism is introduced for the entire nucleation and growth steps, and a proper mathematical model is presented to estimate the gas consumption rate in a constant temperature and pressure process. The proposed model covers the entire dissolution, nucleation, and growth stages. The combined Lax–Wendroff/Crank–Nicolson method is employed to solve the population balance equation for estimation of total surface area of evolved hydrate particles and corresponding particle size distributions. A special class of artificial neural network (known as the Regularization Network) is used to predict the solid–liquid equilibria. The proposed model is successfully validated using experimental data borrowed from the literature for both methane and ethane...

Estimation of the Craniectomy Surface Area by Using Postoperative Images.

Decompressive craniectomy (DC) is a neurosurgical procedure performed to relieve the intracranial pressure engendered by brain swelling. However, no easy and accurate method exists for determining the craniectomy surface area. In this study, we implemented and compared three methods of estimating the craniectomy surface area for evaluating the decompressive effort. We collected 118 sets of preoperative and postoperative brain computed tomography images from patients who underwent craniectomy procedures between April 2009 and April 2011. The surface area associated with each craniectomy was estimated using the marching cube and quasi-Monte Carlo methods. The surface area was also estimated using a simple AC method, in which the area is calculated by multiplying the craniectomy length (A) by its height (C). The estimated surface area ranged from 9.46 to 205.32 cm2, with a median of 134.80 cm2. The root-mean-square deviation (RMSD) between the marching cube and quasi-Monte Carlo methods was 7.53 cm2. Furthermore, the RMSD was 14.45 cm2 between the marching cube and AC methods and 12.70 cm2 between the quasi-Monte Carlo and AC methods. Paired t-tests indicated no statistically significant difference between these methods. The marching cube and quasi-Monte Carlo methods yield similar results. The results calculated using the AC method are also clinically acceptable for estimating the DC surface area. Our results can facilitate additional studies on the association of decompressive effort with the effect of craniectomy.

The Estimate of the Impact of Coccyx Resection in Surgical Field Exposure During Abdominal Perineal Resection Using Preoperative High-Resolution Magnetic Resonance.

To estimate the improvement in surgical exposure by removal of the coccyx, during abdomino-perineal resection (APR), in rectal cancer patients. Retrospective study of 29 consecutive patients with rectal cancer was carried out. Using MR T2 sagittal series, the solid angle was estimated using the angle determined by the anterior resection margin and the tip of coccyx (no coccyx resection) or the tip of last sacral vertebra (coccyx resection). The solid angle provides an estimate of the tridimensional surface area provided by an original angle resulting in the best estimate of the surgeon's view/exposure to the critical dissecting point of choice (anterior rectal wall). The difference ("Gain") in surgical field exposure by removal of the coccyx was compared by the solid angle variation between the two estimates (with and without the coccyx). Routine removal of the coccyx determines an average 42% (95% CI 27-57%) gain in surgical field exposure area facing the anterior rectal wall at the level of the prostate/vagina by the surgeon. Fifteen (51%) patients had ≥30% (median) estimated gain in surgical field exposure by coccygectomy. There was no association between BMI, age or gender and estimated gain in surgical field exposure area. Routine removal of the coccyx during APR may result in an average increase in 42% in surgical field exposure during APR's perineal dissection. Precise estimation of surgical field exposure gain by removal of the coccyx may be predicted by MR sagittal series for each individual patient.

Scale effect on the time dependence of mineral dissolution rates in physically heterogeneous porous media

Hydrologic heterogeneity complicates the time dependent behavior of mineral dissolution rates and introduces large uncertainty in effective surface area estimation. In order to resolve the coupled evolution of mineral dissolution rates and mineral surface area over time in various fluid flow conditions, this study presents multiple reactive transport simulations of anorthite dissolution over 3000 years with 2D latticed random permeability fields on small (1 m × 1 m) and large (400 m × 400 m) domains. Physical heterogeneity is controlled by varying integral scales (λmin and λmax) and variance in permeability distribution (σlnk2) conditions. Chemistry is simplified to a single dissolving primary mineral (anorthite) distributed homogeneously throughout the domain and a single secondary mineral (kaolinite) that is allowed to dissolve or precipitate. In a homogeneous domain, non-normalized effective mineral dissolution rate decreases over time as depletion of the dissolving mineral reduces reaction product concentration. When the reaction rate is normalized either by local or domain-averaged mineral surface area, the rate increases over time approaching the value of the predefined intrinsic rate constant as the effect of saturation state becomes negligible. In a small heterogeneous domain, the effect of physical heterogeneity is largely negligible regardless of the changes in control parameters. In large domains, however, large λ and σlnk2 contribute to develop low-reactive zones that preserve the reactive mineral from dissolution by limiting solute transport to slow diffusion. This preserved mineral fraction provides reactants in late time period resulting in gradual decrease of non-normalized effective mineral dissolution rate. If the rate is normalized by domain-averaged specific surface area, these remaining surface areas over-normalize effective dissolution rates resulting in ∼1.5 orders of magnitude reduction from the homogeneous case.

Heritability estimates of cortical anatomy: The influence and reliability of different estimation strategies

Twin study designs have been previously used to investigate the heritability of neuroanatomical measures, such as regional cortical volumes. Volume can be fractionated into surface area and cortical thickness, where both measures are considered to have independent genetic and environmental bases. Region of interest (ROI) and vertex-wise approaches have been used to calculate heritability of cortical thickness and surface area in twin studies. In our study, we estimate heritability using the Human Connectome Project magnetic resonance imaging dataset composed of healthy young twin and non-twin siblings (mean age of 29, sample size of 757). Both ROI and vertex-wise methods were used to compare regional heritability of cortical thickness and surface area. Heritability estimates were controlled for age, sex, and total ipsilateral surface area or mean cortical thickness. In both approaches, heritability estimates of cortical thickness and surface area were lower when accounting for average ipsilateral cortical thickness and total surface area respectively. When comparing both approaches at a regional level, the vertex-wise approach showed higher surface area and lower cortical thickness heritability estimates compared to the ROI approach. The calcarine fissure had the highest surface area heritability estimate (ROI: 44%, vertex-wise: 50%) and posterior cingulate gyrus had the highest cortical thickness heritability (ROI: 50%, vertex-wise 40%). We also observed that limitations in image processing and variability in spatial averaging errors based on regional size may make obtaining true estimates of cortical thickness and surface area challenging in smaller regions. It is important to identify which approach is best suited to estimate heritability based on the research hypothesis and the size of the regions being investigated.

Estimation of the surface area of a screen-printed carbon electrode modified with gold nanoparticles and cysteine using electrochemical impedance spectroscopy

This work concerns with the estimation of the surface area of a screen-printed carbon electrode (SPCE) modified with gold nanoparticles (AuNPs) and cysteine, using electrochemical impedance spectroscopy (EIS). Interpretation of EIS results was based on charge-transfer reactions at high frequencies, followed by diffusion through the monolayers at lower frequencies. Estimates of the electrode fractional surface coverage (?), active site radius (ra), and the distance between two adjacent sites (2rb) were obtained by assuming that charge transfer occurred at the active sites and that there were planar diffusions of redox species to these sites. Using EIS, fractional surface coverage was estimated to be around 0.467 for EC modified SPCE, 0.497 for ETSC modified SPCE, and 0.25 for ETSTSC modified SPCE. For the EC modified SPCE, the ra and 2rb were estimated to be 14.8 µm and 68 µm. For the ETSC modified SPCE, the estimated ra and 2rb were 14.3 µm and 63.6 µm. The estimated ra and 2rb for ETSTSC were 13.42 µm and 85 µm. respectively. The inactive site areas for EC, ETSC and ETSTSC modified SPCEs were 0.0587 m2, 0.0624 m2, and 0.0314 m2. The results obtained during this research work suggest that modifying SPCEs using gold and cysteine through electrodeposition of AuNPs, linking with thiourea, self-assembly of AuNPs and self-assembly of cysteine (ETSC) resulted in an electrode with sufficiently high surface area that has the potential to be used as a biosensor for skin sensitiser detection.

Crustal structure and properties of Archean cratons of Gondwanaland: similarity and difference

This is a synopsis of available data the on crustal structure and properties of thirteen Archean cratons of Gondwanaland (the cratons of Africa, Australia, Antarctica, South America, and the Indian subcontinent). The data include estimates of surface area, rock age and lithology, Moho depth, thickness of lithosphere and sediments, as well as elevations, all summarized in a table. The cratons differ in size from 0.05 x 106 km2 (Napier craton) to 4 x 106 km2 (Congo craton) and span almost the entire Archean period from 3.8 to 2.5 Ga. Sediments are mostly thin, though reach 7 km in the Congo and West African cratons. Elevations above sea level are from 0 to 2 km; some relatively highland cratons (Kaapvaal, Zimbabwe, and Tanzanian) rise to more than 1 km. On the basis of regional seismic data, the Moho map for cratons has been improved. The Moho diagrams for each craton are constructed. The analysis of the available new data shows that the average Moho depth varies from 33 to 44 km: Pilbara (33 km), Grunehogna (35 km), Sao Francisco (36 km), Yilgarn (37 km), Dharwar (38 km), Tanzanian (39 km), Zimbabwe (39 km), Kaapvaal (40 km), Gawler (40 km), Napier (40 km), West Africa (40 km), Congo (42 km), and Amazon (44 km) cratons. The Moho depth within the cratons is less uniform than it was assumed before: from 28 to 52 km. The new results differ significantly from the earlier inference of a relatively flat Moho geometry beneath Archean cratons. According to the new data, early and middle Archean undeformed crust is characterized by a shallow Moho depth (28-38 km), while late Archean or deformed crust may be as thick as 52 km.

Functional morphometry for the estimation of the alveolar surface area in prematurely-born infants

Conventionally, the alveolar surface area (SA) has been measured by using post-mortem morphometry. Such studies have highlighted that SA in prematurely-born infants is markedly smaller when compared to term-born infants as a result of postnatal impairment or arrest of alveolar development. We herein explore how, non-invasive measurements of the ventilation/perfusion ratio (VA/Q) can be used to estimate SA in prematurely-born surviving, convalescent infants. We also compare SA in prematurely-born infants measured at term-corrected age, to term-born infants using previously published datasets of VA/Q. Fick’s first law of diffusion is employed for the conversion of VA/Q measurements to SA values after correcting for differences in pulmonary perfusion, thickness of the respiratory membrane and alveolar-arterial gradient. We report that SA is fivefold smaller in prematurely-born compared to term-born infants. We conclude that non-invasive measurements of VA/Q can be used for the functional estimation of SA which could, in turn, be used as a future outcome measure in respiratory studies of prematurely-born infants.

Probing Electrochemical Structure-Property Relationships at Non-Porous Monolayer Electrodes of Exfoliated Graphene and MoS2 Single Layers

The electrochemically available surface area and porosity of 2D materials is difficult to control due to the strong aggregation and restacking phenomena that occur when single layers are processed into thin or thick film electrodes. Furthermore, the distributed resistance, the potential for pore-size related effects and the uncertainty in relating estimated surface area and porosity data to the actual electrochemically accessible surface area make measurements of the intrinsic electrochemical performance of these materials difficult to assess. Ideally, electrochemical measurements are carried out on flat, polished or atomically flat electrode surfaces for the evaluation of intrinsic double-layer capacitance and electrochemical rate constants. In this talk, we will discuss our efforts to create large-area monolayers of solution exfoliated 2D materials for electrochemical evaluation in aqueous and non-aqueous electrolytes. Using a modified Langmuir-Blodgett technique, we demonstrate the ability to create uniform and large area monolayers of graphene oxide, thermally reduced graphene oxide as well as 1T and 2H molybdenum disulfide which can be transferred to atomically flat electrode substrates such as highly oriented pyrolytic graphite. These films are found to be stable during electrochemical cycling in various electrolytes and allow us to probe electrochemical properties as a function of 2D material structure without porosity-related artifacts. This model system has been used to probe the changes in double-layer capacitance in both aqueous and non-aqueous electrolytes for graphene-based materials as a function of defect density. It has allowed us to estimate the theoretical limits of graphene-based supercapacitors as a function of graphene “type”. More recently, this analysis has been extended to probe the intrinsic capacitance of the metallic 1T and semiconducting 2H polymorphs of MoS2 as a function of layer number to probe the charging mechanisms at play. The system also offers the ability to probe the capacitance of graphene/MoS2 heterostructures. These and future studies are expected to provide valuable insight into how we might build more energy dense supercapacitors from the optimal combination of 2D materials.

F17. DIFFERENCES IN INTRACRANIAL VOLUME, IQ AND PSYCHOPATHOLOGY IN YOUNG OFFSPRING OF PATIENTS AFFECTED WITH SCHIZOPHRENIA OR BIPOLAR DISORDER

BackgroundOffspring of patients with schizophrenia and bipolar disorder are at increased risk to develop psychopathology. It has been suggested that the development of these disorders may be a result of early neurodevelopmental abnormalities. The intracranial volume (ICV) is a direct marker for neurodevelopment in the early years, as ICV reaches 90% of its full size around the age of five. Interestingly, a smaller ICV is more consistently found in SZ patients, compared to controls, than in bipolar disorder patients. The offspring of these two patients group may provide important information on the putative neurodevelopmental trajectory underlying the development of these disorders. We compared ICV between offspring of at least one parent with SZ (SZo) or BD (BDo) and control offspring (Co) in relation to IQ and the presence of psychopathology.MethodsA large sample of children and adolescents (8–18 years old; 54 SZo, 90 BDo, and 46 Co) was included. T1-weighted (3-Tesla) MRI brain scans were available for 146 participants. Group differences in ICV, global and local brain measures, psychopathology (K-SADS-PL, CBCL/6–18), IQ (WISC-III/WAIS-III), and their interactions were analyzed. FreeSurfer-5.3.0 was used for subcortical and cortical volume, cortical thickness, and cortical surface area estimations. Groups were compared using linear mixed effects modeling, corrected for family dependencies. FDR-correction was applied.ResultsOur main finding was that ICV was significantly smaller in SZo, compared to BDo and Co. IQ was significantly lower in both SZo and BDo, relative to Co, but could not explain the smaller ICV in SZo. ICV was also not explained by psychopathology, even though there was no significant difference in ‘any psychopathology’ between SZo and BDo. There was however some illness specificity as BDo had a higher prevalence of ‘any mood disorder’ as compared with Co, and SZo had a higher prevalence of major depressive disorder and autism spectrum disorders as compared with BDo and Co. After correcting for ICV, the cortex was significantly thinner in SZo compared to BDo and Co, and BDo had larger lateral ventricles than Co. Without correction for ICV, volumes of the total brain and gray matter were significantly smaller in SZo than in BDo and Co. Cortical white matter volume was significantly smaller in SZo as compared with Co.DiscussionIrrespective of a lower IQ and increased presence of psychopathology in both high-risk offspring groups, abnormal early brain development, expressed as smaller ICV, differentiates offspring of patients with schizophrenia from offspring of patients with bipolar disorder and offspring of healthy parents. This suggest that the risk for schizophrenia is, in contrast to that in bipolar disorder, characterized by stunted brain development.

Using X-ray computed tomography and micro-Raman spectrometry to measure individual particle surface area, volume, and morphology towards investigating atmospheric heterogeneous reactions

Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogeneous reactions usually have large variations and may not be relevant to real atmospheric conditions. One of the major reasons for this is the use of bulk samples in laboratory experiments, while particles in the atmosphere are suspended individually. A number of technologies have been developed recently to study heterogeneous reactions on the surfaces of individual particles. Precise measurements on the reactive surface area, volume, and morphology of individual particles are necessary for calculating the uptake coefficient, quantifying reactants and products, and understanding the reaction mechanism better. In this study, for the first time we used synchrotron radiation X-ray computed tomography (XCT) and micro-Raman spectrometry to measure individual CaCO3 particle morphology, with sizes ranging from 3.5–6.5μm. Particle surface area and volume were calculated using a reconstruction method based on software three-dimensional (3-D) rendering. The XCT was first validated with high-resolution field-emission scanning electron microscopy (FE-SEM) to acquire accurate CaCO3 particle surface area and volume estimates. Our results showed an average difference of only 6.1% in surface area and 3.2% in volume measured either by micro-Raman spectrometry or X-ray tomography. X-ray tomography and FE-SEM can provide more morphological details of individual CaCO3 particles than micro-Raman spectrometry. This study demonstrated that X-ray computed tomography and micro-Raman spectrometry can precisely measure the surface area, volume, and morphology of an individual particle.

Estimation of the chemical specific surface area of catalytic nanoparticles by TEM images analysis

Purpose: The purpose of this article is the development of quantitative methods for assessing the quality of nanocomposite materials used in fuel cells. Design/methodology/approach: latinum is the most commonly used catalyst in fuel cells, commonly in the form of nanoparticles deposited on the surface of carbon black. Due to the nanometric size of platinum particles, transmission electron microscopy can be applied to evaluate the produced catalysts. TEM image also allow to determinate the approximate value of the chemical specific surface area) of platinum nanoparticles, but only in case of spherical particles. Findings: In present work, taking into account additional assumptions resulting directly from the analysis of microscopic images, the method of estimation of the particle diameter and the chemical specific surface area for nonsymmetrical (elongated) nanoparticles is present. Research limitations/implications: The presented work presents a method for determining the specific surface of platinum, when their shape is elongated. It is worth noting that the modified formulas for determining the particle diameter and the value of the chemically active specific surface of the platinum nanoparticles of the elongated shape are equivalent to the formulas previously given for spherical particles, if the particle length and its diameter are equal. In this case, patterns for symmetric particles and more general (modified) patterns can be used interchangeably. Practical implications: Development of new and more effective catalysts for fuel cells. Originality/value: The significance of the presented work results from the possibility of using the described method in the catalyst studies during real catalytic processes. It allows comparing catalytic activity after the process, also in unusual conditions and in an aggressive environment, using minimal amounts of material.

Fast, Automated Indoor Light Detection, Classification, and Measurement

Lighting is one of the largest power consumers in the United States and around the globe. To better understand how much energy lighting uses in a building, a lighting audit can be performed. Typically, this is a long and manual process, current solutions require significant effort on the part of the auditor. This paper develops a system using commercially available hardware and custom algorithms that enable a single human operator to quickly cover a large area while estimating light positions, type, and surface area. These tasks are accomplished with an error rate of 6.9% and 13.9%, respectively, with surface area estimation within about a factor of two.

From swollen gels to dried films: Relating the IR spectra of ferrihydrite dried as a film on an ATRIR crystal to aqueous suspensions

In aquatic systems ferrihydrite forms as highly porous aggregates that resemble swollen gels. Much insight into the surface chemistry of ferrihydrite has been gleaned using a technique in which ferrihydrite is dried on to the surface of a crystal that acts as an Attenuated Total Reflectance (ATR) medium for in situ infrared (IR) studies of ligand sorption. In this paper BET N2 adsorption, acid-base titration, H4SiO4 isotherms and the relationship between H4SiO4 sorption and H4SiO4 interfacial oligomerization are used to systematically probe the influence of this drying step on ferrihydrite's surface chemistry. This means that insights into sorption reactions revealed from in situ ATR-IR are can be increasingly related to real environmental systems. Comparing the measured acid-base titration curves to the theoretical curve provide a specific surface area (SSA) estimation of ≈600 and 290 m2 g−1 for the fresh and film-dried ferrihydrite respectively, compared to the BET N2 adsorption values of 240 and 140 m2 g−1 where the fresh ferrihydrite was freeze dried prior to BET measurement. The H4SiO4 isotherms were identical on the two ferrihydrite samples when normalized to the titration derived surface areas. The extent of interfacial H4SiO4 oligomerization provides insights into surface structures. Within experimental uncertainty, the process of drying ferrihydrite into a film did not alter either the general trend in the relationship between sorption and oligomerization, or the extent of oligomerization as a function of surface coverage normalized to the titration derived surface areas. Therefore, in comparable laboratory studies where sorption densities for dried films are compared with fresh suspensions the SSA values of 290 and 600 m2 g−1 respectively should be a reasonable estimate.

Metal and polymer-mediated synthesis of porous crystalline hydroxyapatite nanocomposites for environmental remediation.

This study was focused on the preparation of metal and polymer-mediated porous crystalline hydroxyapatite (HAp) nanocomposites for environmental applications. Four different nano HAp systems were synthesized, namely, microwave irradiated HAp (M1), Zn doped HAp (M2), Mg-doped HAp (M3) and sodium alginate incorporated HAp (M4), and characterized using X-ray diffraction (XRD), Fourier transform infra-red spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, nuclear magnetic resonance (NMR), X-ray fluorescence, thermogravimetric analysis and Brunauer–Emmett–Teller (BET) analyses. Systems M1–M4 showed morphologies similar to coral shapes, polymer-like interconnected structures, sponges and feathery mycelium assemblies. Using XRD, selected area electron diffraction patterns and 1H and 31P CP/MAS solid-state NMR studies, crystallinity variation was observed from highest to lowest in the order of M4 > M1 > M3 > M2. Surface area estimates using BET isotherm reflected the highest surface area for M3, and M1 > M2 > M4. Four systems of M1–M4 were used as potential adsorbent materials for the removal of metal containing azo dye from aqueous system. Adsorption data were correlated to Freundlich and Langmuir isotherm models. According to the results, the highest capacity of 212.8 mg g−1 was exhibited by M4 having mycelium like morphology with alginate groups. This study highlights the possibility of developing HAp nanocomposites for the effective removal of dye contaminants in the environment.

A quantitative assessment of variations in the palm surface area as a percentage of total body surface area within the general population

Healthcare professionals who treat burn patients determine fluid requirements for resuscitation based on an estimation of burned body surface area (BBSA) as a percentage of total body surface area ...

Applicability of the Guggenheim–Anderson–Boer water vapour sorption model for estimation of soil specific surface area

SummarySoil specific surface area (SA) controls fundamental soil processes such as retention of water, ion exchange, and adsorption and release of plant nutrients and contaminants. Conventional methods for determining SA include adsorption of polar or non‐polar fluid molecules with associated advantages and limitations. The Guggenheim–Anderson–Boer (GAB) sorption model accurately characterizes soil water vapour sorption isotherms and is posited as an alternate approach for the determination of SA from water vapour sorption. The present study investigates the GAB model as an alternative to other water sorption‐based modelling approaches to determine SA. Measured water vapour adsorption and desorption isotherms for 321 soil samples were used to parameterize the GAB model, the Brunauer–Emmet–Teller (BET) equation and a film adsorption Tuller–Or (TO) model to estimate SA. For adsorption isotherms, the values of the GAB parameters varied depending on the water activity or relative humidity range of measured data (0.03–0.93 compared with 0.10–0.80), whereas the variation for desorption was minimal. For desorption isotherms, the average water activity value at which the GAB monolayer parameter was obtained was 0.24 for kaolinite‐rich samples, 0.31 for illite‐rich or mixed clay samples, 0.34 for smectitic samples and 0.30 for organic matter‐rich samples, respectively. The GAB model provided reasonable estimates of SA (root mean squared error from 11.6 to 36.4 m2 g−1), in particular for smectite‐rich soil samples, when compared with SA measured by the ethylene glycol monoethyl ether (EGME) method. For kaolinitic samples, however, the BET equation provided the best estimate of EGME‐SA. The SA estimates of the GAB model were comparable to those obtained by the TO adsorption model. Thus, the GAB model provides a good alternative to the TO model (applicable only to adsorption data) or the BET model, which fails when the fraction of swelling clay minerals increases.HighlightsGAB, BET and film adsorption models were parameterized with water vapour sorption data.Water activity at GAB monolayer coverage depended on clay mineralogy.Soil organic matter did not affect water activity at monolayer coverage.Estimates of SA from GAB were in accord with EGME‐measured SA.

Development of radiopaque, biocompatible, antimicrobial, micro-particle fillers for micro-CT imaging of simulated periodontal pockets

ObjectivesApproximately 109 bacteria can be harbored within periodontal pockets (PP) along with inflammatory byproducts implicated in the pathophysiology of systemic diseases linked to periodontitis (PD). Calculation of this inflammatory burden has involved estimation of total pocket surface area using analog data from conventional periodontal probing which is unable to determine the three-dimensional (3-D) nature of PP. The goals of this study are to determine the radiopacity, biocompatibility, and antimicrobial activity of transient micro-particle fillers in vitro and demonstrate their capability for 3-D imaging of artificial PP (U.S. Patent publication number: 9814791 B2). MethodsRelative radiopacity values of various metal oxide fillers were obtained from conventional radiography and micro-computed tomography (μCT) using in vitro models. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays were used to measure the biocompatibility of calcium tungstate (CaWO4) particles by determination of viable keratinocytes percentage (%) after exposure. After introducing an antibacterial compound (K21) to the radiopaque agent, antimicrobial tests were conducted using Porphyromonas gingivalis (P. gingivalis) and Streptococcus gordonii (S. gordonii) strains and blood agar plates. ResultsCaWO4 micro-particle-bearing fillers exhibited an X-ray radiopacity distinct from tooth structures that enabled 3-D visualization of an artificial periodontal pocket created around a human tooth. MTT assays indicated that CaWO4 micro-particles are highly biocompatible (increasing the viability of exposed keratinocytes). Radiopaque micro-particle fillers combined with K21 showed significant antimicrobial activity for P. gingivalis and S. gordonii. SignificanceThe plausibility of visualizing PP with 3-D radiographic imaging using new radiopaque, biocompatible, transient fillers was demonstrated in vitro. Antibacterial (or other) agents added to this formula could provide beneficial therapeutic features along with the diagnostic utility.