3D Voronoi Tessellation for the Study of Mechanical Behavior of Rocks at Different Scales

Numerical investigation of crack damage development and microfracturing in brittle rocks is a widely studied topic, given the number of applications involved. In the framework of the Discrete Element Method (DEM) formulation, the grain-based distinct element model with random polygonal blocks can represent an alternative to the Bonded-Particle Model (BPM) based on particles. Recently, a new engine called Neper has been made available for generating 3D Voronoi grains. The aim of this study is to investigate the applicability of a Neper-based 3D Voronoi tessellation technique for the simulation of the mechanical macro response of rocks. Simulation of unconfined compression tests on synthetic specimens is conducted and a calibration procedure tested. The issue related to scale effects is also addressed, with an application to the case study of a deep geothermal reservoir

Numerical modeling of the tension stiffening in reinforced concrete members via discontinuum models

[prova tipográfica]This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictional elements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete-steel interaction and their macro behavior. The results demonstrate that the proposed phenomenological modeling strategy successfully captures the concrete-steel interaction and provides an accurate estimation of the macro behavior

Promoter G-quadruplexes and transcription factors cooperate to shape the cell type-specific transcriptome

Cell identity is maintained by activation of cell-specific gene programs, regulated by epigenetic marks, transcription factors and chromatin organization. DNA G-quadruplex (G4)-folded regions in cells were reported to be associated with either increased or decreased transcriptional activity. By G4-ChIP-seq/RNA-seq analysis on liposarcoma cells we confirmed that G4s in promoters are invariably associated with high transcription levels in open chromatin. Comparing G4 presence, location and transcript levels in liposarcoma cells to available data on keratinocytes, we showed that the same promoter sequences of the same genes in the two cell lines had different G4-folding state: high transcript levels consistently associated with G4-folding. Transcription factors AP-1 and SP1, whose binding sites were the most significantly represented in G4-folded sequences, coimmunoprecipitated with their G4-folded promoters. Thus, G4s and their associated transcription factors cooperate to determine cell-specific transcriptional programs, making G4s to strongly emerge as new epigenetic regulators of the transcription machinery

A Survey Of Ciidae (Coleoptera, Tenebrionoidea) Of The Hyrcanian Forest (Iran) With New Faunistic Records

Amini, S., Krolik, R., Nozari, J., Farashiani, M. E., Kazerani, F. (2020): A Survey Of Ciidae (Coleoptera, Tenebrionoidea) Of The Hyrcanian Forest (Iran) With New Faunistic Records. Zoodiversity 54 (4): 317-328, DOI: 10.15407/zoo2020.04.317, URL: http://dx.doi.org/10.15407/zoo2020.04.31

Effect of thermocycling on the surface texture and release of titanium particles from titanium alloy (Ti6Al4V) plates and dental implants: An in vitro study

Statement of problem: The release of titanium (Ti) particles from the surface of endosseous dental implants is not well understood. Purpose: The purpose of this in vitro study was to evaluate the effect of thermocycling on the surface texture and release of Ti particles from the surface of dental implants. Material and methods: Three MSI dental implants and 3 Ti alloy (Ti6Al4V) plates were divided into 6 subgroups (n=3). Specimens in each group were subjected to 0 (control group), 100, 200, 500, 1000, and 2000 thermocycles. After each cycling process, artificial saliva was collected, and the concentrations of released Ti particles were quantified by inductively coupled plasma-mass spectrophotometry (ICP-MS). The surfaces of the dental implants and Ti plates were evaluated before and after thermocycling by scanning electron microscopy (SEM), and SEM images were analyzed by using the ImageJ software program. Data were analyzed by mixed-model ANOVA and post hoc Tukey tests (α=.05). Results: The greatest Ti release was seen after 2000 thermocycles. After increasing the number of cycles, additional Ti particles were released. SEM images of the surfaces of the dental implants and Ti plates displayed significant changes in surface texture. Conclusions: Thermocycling continuously removed the protective TiO2 layer on the surface of dental implants, resulting in the release of Ti particles. The surface treatment and texture did not affect the release of Ti particles

Effect of thermocycling on the surface texture and release of titanium particles from titanium alloy (Ti6Al4V) plates and dental implants: An in vitro study

Statement of problem: The release of titanium (Ti) particles from the surface of endosseous dental implants is not well understood. Purpose: The purpose of this in vitro study was to evaluate the effect of thermocycling on the surface texture and release of Ti particles from the surface of dental implants. Material and methods: Three MSI dental implants and 3 Ti alloy (Ti6Al4V) plates were divided into 6 subgroups (n=3). Specimens in each group were subjected to 0 (control group), 100, 200, 500, 1000, and 2000 thermocycles. After each cycling process, artificial saliva was collected, and the concentrations of released Ti particles were quantified by inductively coupled plasma-mass spectrophotometry (ICP-MS). The surfaces of the dental implants and Ti plates were evaluated before and after thermocycling by scanning electron microscopy (SEM), and SEM images were analyzed by using the ImageJ software program. Data were analyzed by mixed-model ANOVA and post hoc Tukey tests (α=.05). Results: The greatest Ti release was seen after 2000 thermocycles. After increasing the number of cycles, additional Ti particles were released. SEM images of the surfaces of the dental implants and Ti plates displayed significant changes in surface texture. Conclusions: Thermocycling continuously removed the protective TiO2 layer on the surface of dental implants, resulting in the release of Ti particles. The surface treatment and texture did not affect the release of Ti particles