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Although opioids are useful narcotic analgesics in clinical settings, their misuse and addiction in the United States of America and other countries are rapidly increasing. Therefore, the development of abuse-deterrent formulations is an urgent issue. We herein investigated how to select the ratio of an opioid and the opioid receptor antagonist, naloxone in abuse-deterrent formulations for mice. The conditioned place preference (CPP) test was used to evaluate the rewarding effects of abused drugs. The opioids morphine (30 μmol/kg), oxycodone (3 μmol/kg), fentanyl (0.4 μmol/kg), and buprenorphine (0.5 μmol/kg) significantly induced place preference in mice. We also examined the optimal ratio of naloxone and opioids to inhibit the rewarding effects of the latter. Naloxone (3-5 μmol/kg) effectively inhibited place preference induced by the opioids tested. We calculated theoretical drug doses that exerted the same pharmacodynamic effects based on two parameters: μ-opioid receptor binding affinity and blood-brain barrier (BBB) permeability. Theoretical doses were very close to the drug doses at which mice showed place preference. Therefore, the CPP test is useful as a behavioral method for evaluating abuse-deterrent formulations of opioids mixed with an antagonist. The ratio of naloxone with opioids, at which mice did not show place preference, may be an effective index for developing abuse-deterrent formulations. Ratios may be calculated for other opioids based on μ-opioid receptor binding affinity and BBB permeability.

The brominated flame retardant 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is extensively used, stable, and difficult to degrade in the environment. The existence of BDE-47 could pose a certain risk to the environment and human health. However, the biotransformation mechanisms of BDE-47 by microorganisms remain unclear. In this study, aerobic degradation of BDE-47 by

There has been extensive discussion of the “Replication Crisis” in many fields, including genome-wide association studies (GWAS). We explored replication in a mouse model using an advanced intercross line (AIL), which is a multigenerational intercross between two inbred strains. We re-genotyped a previously published cohort of LG/J x SM/J AIL mice (F34; n = 428) using a denser marker set and genotyped a new cohort of AIL mice (F39-43; n = 600) for the first time. We identified 36 novel genome-wide significant loci in the F34 and 25 novel loci in the F39-43 cohort. The subset of traits that were measured in both cohorts (locomotor activity, body weight, and coat color) showed high genetic correlations, although the SNP heritabilities were slightly lower in the F39-43 cohort. For this subset of traits, we attempted to replicate loci identified in either F34 or F39-43 in the other cohort. Coat color was robustly replicated; locomotor activity and body weight were only partially replicated, which was inconsistent with our power simulations. We used a random effects model to show that the partial replications could not be explained by Winner’s Curse but could be explained by study-specific heterogeneity. Despite this heterogeneity, we performed a mega-analysis by combining F34 and F39-43 cohorts (n = 1,028), which identified four novel loci associated with locomotor activity and body weight. These results illustrate that even with the high degree of genetic and environmental control possible in our experimental system, replication was hindered by study-specific heterogeneity, which has broad implications for ongoing concerns about reproducibility.

Skin cutaneous melanoma (SKCM) is the most aggressive and fatal type of skin cancer. Its highly heterogeneous features make personalized treatments difficult, so there is an urgent need to identify markers for early diagnosis and therapy. Detailed profiles are useful for assessing malignancy potential and treatment in various cancers. In this study, we constructed a co-expression module using expression data for cutaneous melanoma. A weighted gene co-expression network analysis was used to discover a co-expression gene module for the pathogenesis of this disease, followed by a comprehensive bioinformatics analysis of selected hub genes. A connectivity map (CMap) was used to predict drugs for the treatment of SKCM based on hub genes, and immunohistochemical (IHC) staining was performed to validate the protein levels. After discovering a co-expression gene module for the pathogenesis of this disease, we combined GWAS validation and DEG analysis to identify 10 hub genes in the most relevant module. Survival curves indicated that eight hub genes were significantly and negatively associated with overall survival. A total of eight hub genes were positively correlated with SKCM tumor purity, and 10 hub genes were negatively correlated with the infiltration level of CD4+ T cells and B cells. Methylation levels of seven hub genes in stage 2 SKCM were significantly lower than those in stage 3. We also analyzed the isomer expression levels of 10 hub genes to explore the therapeutic target value of 10 hub genes in terms of alternative splicing (AS). All 10 hub genes had mutations in skin tissue. Furthermore, CMap analysis identified cefamandole, ursolic acid, podophyllotoxin, and Gly-His-Lys as four targeted therapy drugs that may be effective treatments for SKCM. Finally, IHC staining results showed that all 10 molecules were highly expressed in melanoma specimens compared to normal samples. These findings provide new insights into SKCM pathogenesis based on multi-omics profiles of key prognostic biomarkers and drug targets. GPR143 and SLC45A2 may serve as drug targets for immunotherapy and prognostic biomarkers for SKCM. This study identified four drugs with significant potential in treating SKCM patients.

This paper aims at presenting an analytical method for evaluating the calcium diffusion coefficient of partially leached cement paste. The analytical method is developed based on a two-scal...

Background Early childhood caries is an urgent public health concern. The aim of this study was to investigate salivary proteomic biomarkers for the surveillance of changes in the high-risk status of early childhood caries. The process involves the screening of specific salivary peptides that were differentially expressed only under dynamic changes in individual caries status. Methods Stimulated whole saliva samples were collected from 28 kindergarten children aged 3–4 years in Beijing at baseline and 3 months and 6 months after baseline. A total of 68 samples were collected. In terms of their caries status and progress during the observation period, participants were divided into 3 groups; 7 in the non-caries recurrence group, 6 in the caries recurrence group, and 15 in the healthy control group. Salivary peptides that exhibited no significant differences in cross-sectional comparisons between different groups of caries status but only expressed differentially along with dynamic changes of individual caries were screened using the technique of magnetic beads combined with matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The technique of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) was employed to identify the proteins from which these peptides were derived. Results We found two salivary peptides differentially expressed only under dynamic changes in individual caries status in the above comparisons; mass-to-charge ratio (m/z) values of the two peptides were 1045.9 and 2517.6, respectively (P m/z values of 1045.9 and 2517.6 were identified as submandibular gland androgen regulatory protein 3B (SMR-3B) and mucin-7, respectively. Conclusions Two proteins in children’s saliva, namely SMR-3B and mucin-7, have the potentiality to serve as candidate biomarkers for dynamic surveillance of changes in high-risk status of early childhood caries.

In a previous genome-wide association study (GWAS) using outbred Carworth Farms White (CFW) mice, we identified a locus that influenced the stimulant response to methamphetamine and colocalized with an eQTL for Azi2. Based on those findings, we hypothesized that heritable differences in Azi2 expression were causally related to the differential response to methamphetamine. To test that hypothesis, we created a mutant Azi2 allele on an inbred C57BL/6J background. The mutant allele enhanced the locomotor response to methamphetamine. However, the GWAS had suggested that lower Azi2 would decrease the locomotor response to methamphetamine. We also sought to explore the mechanism by which Azi2 influenced methamphetamine sensitivity. A recent publication reported that the 3'UTR of Azi2 mRNA downregulates the expression of Slc6a3, which encodes the dopamine transporter, which is a key target of methamphetamine. We evaluated the relationship between Azi2, Azi2 3'UTR and Slc6a3 expression in the ventral tegmental area of wildtype, mutant Azi2 heterozygotes and mutant Azi2 homozygotes and in a new cohort of outbred CFW mice where both allele mapped in our prior GWAS were segregating. We did not observe any correlation between Azi2 and Slc6a3 in either cohort. However, RNA sequencing confirmed that the Azi2 mutation altered Azi2 expression and also revealed a number of potentially important genes and pathways that were regulated by Azi2, including the metabotropic glutamate receptor group III pathway and nicotinic acetylcholine receptor signaling pathway. Our results support a role for Azi2 in methamphetamine sensitivity; however, the exact mechanism does not appear to involve regulation of Slc6a3.

In order to better understand the composition and driving factors of the bacterial community in Mollisols, we selected 9 representative facility agricultural lands in Mollisol area of China for sampling, and described it on a larger spatial scale. Soil bacterial community structure in these 9 regions (determined by high-throughput sequencing analysis) showed significant differences at the genus level. The correlation between bacterial community composition and soil properties, contaminants and geographical latitude showed that the diversity of bacterial community was still strongly correlated with pH and SOM under the influence of phthalates (P 0.05). Principal component Analysis (PCA) showed that soil properties (i.e. pH, organic matter, stacking density, the content of nitrogen, potassium, phosphorus) and PAEs level rather than geographic latitude were main drivers of differences in bacterial community structure. These factors account for 73.04% of the total variation of the bacterial community. Among them, PAEs act as a typical pollutant is the main factor driving the composition of bacterial community in facility agriculture Mollisols. This shows that PAEs is a potential pollution risk factor, which has important guiding significance for the sustainable and healthy development of agriculture in Mollisol area.

Identification of the cis-regulatory elements controlling cell-type specific gene expression patterns is essential for understanding the origin of cellular diversity. Conventional assays to map regulatory elements via open chromatin analysis of primary tissues is hindered by sample heterogeneity. Single cell analysis of accessible chromatin (scATAC-seq) can overcome this limitation. However, the high-level noise of each single cell profile and the large volume of data pose unique computational challenges. Here, we introduce SnapATAC, a software package for analyzing scATAC-seq datasets. SnapATAC dissects cellular heterogeneity in an unbiased manner and map the trajectories of cellular states. Using the Nyström method, SnapATAC can process data from up to a million cells. Furthermore, SnapATAC incorporates existing tools into a comprehensive package for analyzing single cell ATAC-seq dataset. As demonstration of its utility, SnapATAC is applied to 55,592 single-nucleus ATAC-seq profiles from the mouse secondary motor cortex. The analysis reveals ~370,000 candidate regulatory elements in 31 distinct cell populations in this brain region and inferred candidate cell-type specific transcriptional regulators., Single cell analysis of transposase-accessible chromatin is deepening our understanding on the origins of cellular diversity, yet methods are limited by data sparsity. Here, the authors introduce SnapATAC, a pipeline to resolve cellular heterogeneity and reveal candidate regulatory elements across different cell populations.

The chloride diffusivity of concrete is an important parameter for assessing the long-term durability of coastal concrete structures. The purpose of this paper is to present a three-dimensional random walk algorithm (RWA) for estimating the chloride diffusivity of concrete. By analyzing the size distribution of aggregates, the equivalent interfacial transition zone (ITZ) thickness is derived in an analytical manner. Each aggregate is combined with the surrounding ITZ to construct an equivalent aggregate model (EAM) and the chloride diffusivity is formulated. It is found that the equivalent ITZ thickness decreases with the increase of practical ITZ thickness and aggregate volume fraction. The aggregate gradation influences the equivalent ITZ thickness to a certain extent. The relative chloride diffusivity of the equivalent aggregate is almost directly and inversely proportional to the equivalent ITZ thickness and the aggregate radius, respectively. The numerical results show that, when the EAM is adopted, the computational time is greatly reduced. With the EAM, concrete can be modeled as a two-phase material and the chloride diffusivity is estimated by applying the RWA. It is shown that, with the increase of mean square displacement and number of Brownian particles, the average chloride diffusivity of concrete approaches a stable value. Finally, through comparison with experimental data, the validation of the RWA is preliminarily verified.

Methamphetamine is a widely abused psychostimulant. In a previous genome-wide association study (GWAS), we identified a locus that influenced the stimulant response to methamphetamine. That locus was also an eQTL for the gene Azi2. Based on those findings, we hypothesized that heritable differences in the expression of Azi2 were causally related to the differential response to methamphetamine. In this study, we created a mutant Azi2 allele that caused lower Azi2 expression and enhanced the locomotor response to methamphetamine; however, based on the GWAS findings, we had expected lower Azi2 to decrease rather than increase the stimulant response to methamphetamine. We then sought to explore the mechanism by which Azi2 influenced methamphetamine sensitivity. A recent publication had reported that the 3’UTR of Azi2 mRNA downregulates the expression of Slc6a3, which encodes the dopamine transporter (DAT), which is a key target of methamphetamine. We evaluated the relationship between Azi2/Azi2 3’UTR and Slc6a3 expression in the VTA in the mutant Azi2 mice and in a new cohort of CFW mice. We did not observe any correlation between Azi2 and Slc6a3 in the VTA in either cohort. However, RNA sequencing confirmed that the Azi2 mutation altered Azi2 expression and also revealed a number of potentially important genes and pathways that were regulated by Azi2, including the metabotropic glutamate receptor group III pathway and nicotinic acetylcholine receptor signaling pathway. Our results support a role for Azi2 in methamphetamine sensitivity; however, the exact mechanism does not appear to involve regulation of Slc6a3 and thus remains unknown.

Graphene shows extraordinary optical and electrical properties that can be combined with some metallic micro-nanostructures. We experimentally investigated the electric tuning of Raman scattering in both a monolayer graphene and a monolayer graphene with gold nanorods (AuNRs). It is found when a gate voltage is applied on graphene from −30 to 30 V, the G and 2D peaks of the graphene structures can both be tuned. More importantly, the tuning can be significantly enhanced by the AuNRs on graphene, including the change of the peak position, width and the intensity. Our findings may provide a new way for studying enhanced tunable Raman scattering of graphene structures.

This paper develops a highly efficient numerical method for estimating the chloride diffusivity of mature cement paste. In the method, the two-dimensional microstructure of cement paste is ...

Identification of the cis-regulatory elements controlling cell-type specific gene expression patterns is essential for understanding the origin of cellular diversity. Conventional assays to map regulatory elements via open chromatin analysis of primary tissues is hindered by heterogeneity of the samples. Single cell analysis of transposase-accessible chromatin (scATAC-seq) can overcome this limitation. However, the high-level noise of each single cell profile and the large volumes of data could pose unique computational challenges. Here, we introduce SnapATAC, a software package for analyzing scATAC-seq datasets. SnapATAC can efficiently dissect cellular heterogeneity in an unbiased manner and map the trajectories of cellular states. Using the Nyström method, a sampling technique that generates the low rank embedding for large-scale dataset, SnapATAC can process data from up to a million cells. Furthermore, SnapATAC incorporates existing tools into a comprehensive package for analyzing single cell ATAC-seq dataset. As demonstration of its utility, SnapATAC was applied to 55,592 single-nucleus ATAC-seq profiles from the mouse secondary motor cortex. The analysis revealed ∼370,000 candidate regulatory elements in 31 distinct cell populations in this brain region and inferred candidate transcriptional regulators in each of the cell types.

The chloride diffusion coefficient of concrete plays an essential role in the durability assessment and design of concrete structures built in chloride-laden environments. The purpose of this paper is to present an effective medium method (EMM) for evaluating the chloride diffusion coefficient of mature fly ash cement paste. In this method, a numerical method is used to estimate the degrees of hydration of cement and fly ash. Fly ash cement paste is then modeled as a two-phase composite material, composed of a solid phase and a pore space. By introducing the percolation theory, the EMM is modified to derive the chloride diffusion coefficient of fly ash cement paste in an analytical manner. To verify the EMM, a chloride diffusion test of fly ash cement paste at a curing age of up to 540 days is conducted. It is shown that, within a reasonable fly ash content, a larger fly ash content and/or curing age results in a smaller chloride diffusion coefficient. The chloride diffusion coefficient decreases with a decreasing water/binder ratio. Finally, the validity of the EMM is verified with experimental results.

Replication is considered to be critical for genome-wide association studies (GWAS) in humans, but is not routinely performed in model organisms. We explored replication using an advanced intercross line (AIL) which is the simplest possible multigenerational intercross. We re-genotyped a previously published cohort of LG/J x SM/J AIL mice (F34; n=428) using a denser marker set and also genotyped a novel cohort of AIL mice (F39-43; n=600) for the first time. We identified 110 significant loci in the F34cohort, 36 of which were new discoveries attributable to the denser marker set; we also identified 27 novel significant loci in the F39-43cohort. For traits measured in both cohorts (locomotor activity, body weight, and coat color), the genetic correlations were high, although, the F39-43cohort showed systematically lower SNP-heritability estimates. We then attempted to replicate loci identified in either F34or F39-43in the other cohort. Albino coat color was robustly replicated; we observed only partial replication of associations for locomotor activity and body weight. Finally, we performed a mega-analysis of locomotor activity and body weight by combining F34and F39-43cohorts (n=1,028), which identified four novel loci. The incomplete replication was inconsistent with simulations we performed to estimate our power to replicate. This may reflect: 1) false positives errors in the discovery cohort, 2) environmental or genetic heterogeneity between the two samples, or 3) the systematic over estimation of the effect sizes at significant loci (“Winner’s Curse”). Our results demonstrate that it is difficult to replicate GWAS results even when using similarly sized discovery and replication cohorts drawn from the same population.

This paper presents an analytical solution for Young's modulus of concrete with the aggregate aspect ratio effect. By taking the interfacial transition zone (ITZ)-coated aggregate as an ‘equivalent aggregate', the three-phase concrete is reduced to a two-phase composite material. The interaction direct derivative estimate is then adopted to derive an analytical solution for Young's modulus of concrete. After the validity of the analytical solution is verified with three sets of experimental results, the effects of various key factors on Young's modulus of concrete are evaluated quantitatively. The numerical results indicate that Young's modulus of concrete increases with an increase in maximum aggregate size, aggregate aspect ratio and Young's modulus of the aggregate, but decreases with increasing ITZ thickness. It is also found that the aggregate gradation has a certain influence on Young's modulus of concrete.

With the increasingly complex of the market competition environment, enterprise competition is increasingly fierce, more and more enterprises has realized the importance of innovation for enterprise survival and development. Currently, the development of SMEs is not optimistic, due to lack of sustainable development capacity, and the more prominent problem is the lack of core competitiveness. The paper researches the core competitiveness of SMEs by the empirical analysis, some conclusions are drawn. Keywords-small and medium-sized enterprises (SMEs); core competitiveness; regression analysis; empirical analysis

The Young’s modulus of concrete is an important mechanical parameter for assessing the stiffness of concrete structures. The objective of this paper is to present an analytical method for evaluating the Young’s modulus of concrete with spheroidal aggregates. In this method, the interfacial transition zone (ITZ) between aggregates and the bulk cement paste is treated as an independent phase. To reduce mathematical complexity, the three-phase concrete is decomposed into two two-phase composite materials and modeled through a two-step procedure. After the validity of the analytical method is verified with three sets of experimental data, a sensitivity analysis is conducted to quantify various factors that affect the Young’s modulus of concrete. The numerical results show that the Young’s modulus of concrete increases with the increase of the maximum size and aspect ratio of aggregate but decreases by increasing the ITZ thickness. It is also shown that the aggregate gradation influences the Young’s mo...

Owing to its importance to the structural analysis and design of cement-based materials, it is essential to determine Young’s modulus of concrete. This paper presents a numerical method for predicting Young’s modulus of concrete with aggregate shape effect. In the numerical method, aggregate particles are assumed to be elliptical and distributed within a rectangular concrete element with periodic boundary conditions by introducing an overlap criterion for two elliptical aggregate particles. The method modifies the lattice model to take account of the mechanical properties of each phase constituent of concrete in the analysis of stress. After the validity of the developed numerical method is verified with three independent sets of experimental results, the effects of the maximum aggregate diameter, aggregate gradation, interfacial transition zone (ITZ) thickness, and aggregate shape on Young’s modulus of concrete are evaluated in a quantitative manner. It is found that Young’s modulus of concrete increases with the increase of the maximum aggregate diameter and aggregate aspect ratio but decreases by increasing the ITZ thickness. It is also found that the aggregate gradation has a significant influence on Young’s modulus of concrete. The paper concludes that the numerical method developed in the paper can predict Young’s modulus of concrete with an average relative error smaller than 7%.

Owing to their importance to the structural analysis and evaluation of cement-based materials, it is essential to determine the mechanical properties of cement paste. This paper presents a simple three-step analytical scheme for predicting the elastic moduli of hardened cement paste. In this scheme, hardened cement paste is modeled as a multiphase composite material, composed of unhydrated cement, C-S-H, CH, and capillary pores and further represented by five two-phase composite spheres. The elastic moduli of hardened cement paste are obtained in terms of the volume fractions and elastic moduli of unhydrated cement, C-S-H, CH, and capillary pores by the three-step scheme. Finally, the validity of the three-step scheme is verified with three independent sets of experimental data. The paper concludes that, when the water-cement ratio is in the range of 0.4–0.6, the simple three-step analytical scheme presented in the paper can predict the elastic moduli of hardened cement paste with an average relative erro...

Due to its importance to the durability assessment and design of reinforced concrete structures located in a marine or deicing salt environment, it is essential to determine the chloride diffusivity of hardened cement paste. This paper presents an analytical solution for the chloride diffusivity of hardened cement paste. By modeling hardened cement paste as a two-phase composite material, composed of gel and capillary pores and solid cement gel, an analytical solution is derived for the chloride diffusivity of hardened cement paste based on the general effective medium theory. A parameter involved in the analytical solution is then determined by experimental calibration. After verifying the analytical solution with experimental results obtained from the literature, the effects of the water/cement ratio and the degree of hydration on the chloride diffusivity of hardened cement paste are evaluated in a quantitative manner. It is found that the chloride diffusivity of hardened cement paste with a water/cement ratio of 0.7 is three orders of magnitude larger than that with a water/cement ratio of 0.3 and that the extent to which the degree of hydration influences the chloride diffusivity of hardened cement paste is in the range of 50 to 80% when the degree of hydration varies from 0.5 to 1.0. The paper concludes that the analytical solution presented in the paper can predict the chloride diffusivity of hardened cement paste with reasonable accuracy.

In predicting the chloride diffusivity of concrete as a three-phase material, the morphological characteristics of the three phases, the physical properties of each phase constituent material, and the interactions of the three phases in the concrete matrix should all be taken into account. The present paper attempts to develop an analytical method to achieve this. A three-phase composite sphere model for the concrete matrix is proposed to represent the heterogeneous nature of concrete and a closed form solution for the chloride diffusivity of concrete is derived. After verifying the derived closed form solution with experimental results, the effects of key factors that affect the chloride diffusivity of concrete, namely the chloride diffusivity and thickness of the interfacial transition zone (ITZ), the maximum aggregate diameter, and the aggregate gradation are examined in a quantitative manner. It is found in the paper that the most important factor influencing the chloride diffusivity of concrete is the chloride diffusivity of ITZ. When the aggregate volume fraction is equal to 0.8, the relative chloride diffusivity of concrete to cement paste for a given relative chloride diffusivity of ITZ to cement paste at 10 is almost four times that for a given relative chloride diffusivity of ITZ to cement paste at 2. The second most important factor is the thickness of ITZ. When the aggregate volume fraction is equal to 0.8, the relative chloride diffusivity of concrete to cement paste for a given ITZ thickness at 0.05 mm increases by 76% as compared to that for a given ITZ thickness at 0.02 mm. The least important factors are the maximum aggregate diameter and aggregate gradation. The extent to which they influence the chloride diffusivity of concrete is in the range of 10 — 55%. The paper concludes that the closed form solution derived here can predict the chloride diffusivity of concrete with reasonable accuracy.

In view of the importance of percolation of the interfacial transition zones (ITZs) in concrete to its transport properties, it is necessary to determine the ITZ percolation threshold for any aggregate gradation and ITZ thickness. This paper presents a numerical method for predicting the ITZ percolation threshold of concrete. To represent the mesostructure of concrete as realistically as possible, a simulation algorithm for the distribution of aggregate particles and ITZs in concrete with periodic boundary conditions is proposed. By analyzing and studying the numerical results, it is shown in this paper that, for a given aggregate volume fraction and element size, the ITZ percolation probability tends to be a constant for a sufficient number of simulations and that the slope of the ITZ percolation probability curve becomes vertical as the element size increases. Finally the results produced by the proposed numerical method are verified by experimental results obtained from the research literature. Based on the results presented in this paper, the effects of the ITZ thickness, the maximum aggregate diameter, and the aggregate gradation on the ITZ percolation threshold are evaluated in a quantitative manner. It can be concluded that the numerical method developed can be used to predict the ITZ percolation threshold with reasonable accuracy.

The purpose of this paper is to evaluate the effect of aggregate shape on the chloride diffusivity of concrete through laboratory experiments and theoretical analysis. In the experiment, three types of crystal glass spheroids with aspect ratios of 1, 2, and 3 are used as coarse aggregate. The experimental results show that the chloride diffusivity of concrete decreases with an increase in aggregate aspect ratio. When the coarse aggregate volume fraction is equal to 0.1, 0.2, and 0.3, the chloride diffusivity of concrete at an aggregate aspect ratio of 3 is, on average, smaller than that at an aggregate aspect ratio of 1 by 5.29%, 11.4%, and 19.6%, respectively. An analytical approximate is derived for the chloride diffusivity of concrete with spheroidal aggregates and verified with the experimental results. The analytical approximate can predict the chloride diffusivity with an average relative error of less than 8%.

In view of the importance of the interfacial transition zone (ITZ) to the macro-properties of concrete, it is essential to study the ITZ percolation characteristics of concrete. This paper presents a numerical method for predicting the ITZ percolation threshold of concrete with elliptical aggregates. With the simulated mesostructure of concrete with periodic boundary conditions, the ITZ percolation threshold is determined by the forest fire algorithm. Based on the numerical results, the effects of various factors on the ITZ percolation threshold are evaluated in a quantitative manner. It is found that the ITZ percolation threshold increases with the increase of the aspect ratio and maximum diameter of elliptical aggregates, but decreases by increasing the ITZ thickness. It is also found that the aggregate gradation has a significant influence on the ITZ percolation threshold.

Interfacial transition zone (ITZ) in concrete is characterized typically by its high porosity and therefore has a significant influence, particularly, on the transport properties of concrete. To study the transport mechanism of ions and fluids in concrete, it is essential to determine the percolation threshold of ITZs in concrete and to evaluate the effects of attributing factors on it. This paper presents a forest fire algorithm for the prediction of the percolation threshold of ITZs in concrete. Based on the simulated mesostructure of concrete with periodic boundary conditions, the ITZ percolation probability is determined numerically. The effect of the element size on the ITZ percolation probability is then discussed. Finally, the proposed numerical algorithm is verified with experimental results obtained from the research literature.