Mixed mode cracking in concrete keeps being a challenging issue in computational fracture mechanics. While uncracked concrete develops cracks perpendicular to the direction of the maximum principal ...tensile stress, the crack edges will expectedly open, mutually slide, and transmit both normal and shearing stresses. In the present formulation, we replace the damage band with a regularized strain band by enriching the space of the approximating functions in compliance with the regularized extended finite element model developed by the authors. Our clue is that a discriminant factor to choose the appropriate expression of the regularized strain relies upon the concept of stress compatibility modified to consider aggregate interlock. In particular, we resort to a simplified phenomenological saw-tooth model of the crack surface asperities. We show the capability of the methodology to capture both structural behavior and crack paths in a set of bending tests carried out on concrete specimens. Though phenomenological, the resulting approach is novel, conceptually simple and reliable for it directly reproduces the expected kinematics and structural results.
•The localized strain is modeled through the regularized XFEM.•Stress compatibility and aggregate interlock are considered.•A saw-tooth model of the crack surface asperities is used.•The regularization length is linked with the width of the FPZ.•Both structural results and crack paths are captured.
Trichloroanisole (TCA) is one of the most significant contaminants in cork stoppers. The presence of TCA leads to an unpleasant odor known as cork taint, resulting in high economic losses for the ...cork and wine industries. Hence, the detection, quantification, and characterization of TCA are essential to address this concern. The present study investigates the electron-driven fragmentation pathways of TCA through electron ionization mass spectrometry as a function of electron energy (0100 eV), and the results are supported by theoretical characterization of ionization potentials, dissociation thresholds, and electron ionization cross sections. The appearance energies of ten cations were measured, including the first experimental evaluation of the molecule's ionization energy at 8.8 0.3 eV, in excellent agreement with the calculations (8.83 eV). For lower energies, around 20 eV, the parent cation accounted for more than 60% of the total ion signal, followed by its demethylated fragment. Taken together, these ion signals could be used as fingerprints of TCA in industrial quality control by low-energy electron ionization mass spectrometry. Fifty other fragments have been identified at higher electron energies, revealing the very rich fragmentation pattern of TCA.
This work probes electron-driven ionization of TCA. New fragment ions are identified by mass spectrometry and experimental appearance energies show excellent agreement with calculated threshold energies for the most significant pathways.
•The present study formulates a novel FE constitutive model with multi-surface plasticity and anisotropic multi-surface damage.•The model correctly captures the sensitivity of the material to ...loading-directionality, and ductile and brittle phenomena.•We define a set of plasticity and damage activation criteria and three damage variables corresponding to distinct stress states.•We formulate the algorithmic treatment of the relevant tangent constitutive matrix.•We show that the proposed formulation performs better than analogous existing models.
Restoration of ancient wooden beams and design of smart wood-based structures are gaining an increasing interest in building industry. In this context, the computational challenge is to develop numerical constitutive models that account for the complex and strongly non-linear behaviour of wood. Wood is a natural composite exhibiting pronounced orthotropic behaviour, and markedly different properties along the parallel and transverse-to-the-fiber directions. It displays a strongly non-linear mechanical behavior, almost elasto-plastic at compressive loadings and elasto-damaging when subjected to tensile and shearing stresses. We devise here a novel constitutive model for wood with a multi-surface failure domain resulting from a set of plastic laws for compressive failure modes and orthotropic damage laws for tensile/shear failure modes. The advantage over existing formulations is that the coexistence of anisotropic damage and plasticity constitutive laws allows to correctly capture brittle failure induced by strain localization as well as the possible occurrence of ductile plastic behavior. Furthermore, the present contribution shows how to numerically treat the simultaneous presence of anisotropic damage and plasticity in a general algorithmic multi-surface framework. It is shown that the obtained numerical results satisfactorily fit to experimental data.
Over the last few years, there has been increasing interest in the use of amorphous carbon thin films with low secondary electron yield (SEY) to mitigate electron multipacting in particle ...accelerators and RF devices. Previous works found that the SEY increases with the amount of incorporated hydrogen and correlates with the Tauc gap. In this work, we analyse films produced by magnetron sputtering with different contents of hydrogen and deuterium incorporated via the target poisoning and sputtering of CxDy molecules. XPS was implemented to estimate the phase composition of the films. The maximal SEY was found to decrease linearly with the fraction of the graphitic phase in the films. These results are supported by Raman scattering and UPS measurements. The graphitic phase decreases almost linearly for hydrogen and deuterium concentrations between 12% and 46% (at.), but abruptly decreases when the concentration reaches 53%. This vanishing of the graphitic phase is accompanied by a strong increase of SEY and the Tauc gap. These results suggest that the SEY is not dictated directly by the concentration of H/D, but by the fraction of the graphitic phase in the film. The results are supported by an original model used to calculate the SEY of films consisting of a mixture of graphitic and polymeric phases.
•We consider damage under tensile/shear stresses and plasticity.•The model transitions from the continuous damage plasticity regime of Part I to a regularized XFEM regime.•The transition is ...smooth.•Failure is correctly captured.
The present study investigates the modelling capabilities offered by the multi-surface damage-plasticity FE-formulation illustrated in Part I 1 when integrated with a regularized extended finite element model. The aim is to tackle discontinuous displacements and interfaces. In particular, we show how to embed a regularized discontinuity within an element, carry out the transition from the continuous to the regularized discontinuous regime and obtain physically consistent results. We present a wide set of applications ranging from brittle to ductile failure, displaying the effectiveness of the proposed FE-approach versus the experimental results.
The genetic diversity of the BoLA‐DRB3 gene has been reported in different cattle breeds owing to its central role in the immune response. However, it is still unknown in hundreds of cattle breeds, ...especially native populations. Here, we studied BoLA‐DRB3 genetic diversity in Highland Creole cattle (CrAl) from Western Bolivia, raised at altitudes between 3800 and 4200 m. DNAs from 48 CrAl cattle were genotyped for BoLA‐DRB3 exon 2 alleles using polymerase chain reaction‐sequence‐based typing (PCR‐SBT). The results were compared with 1341 previously reported data from Tropical Creole cattle and other breeds raised in the region. Twenty‐three BoLA‐DRB3 alleles were identified in CrAl, including the BoLA‐DRB3*029:02 variant previously detected in other Creole cattle. Observed and expected heterozygosity were 0.87 and 0.93, respectively. Nucleotide diversity and the number of pairwise difference values were 0.078 and 19.46, respectively. The average number of nonsynonymous and synonymous substitutions were 0.037 and 0.097 for the entire BoLA‐DRB3 exon 2, and 0.129 and 0.388 for the antigen‐binding site, respectively. Venn analysis and the review of the IPD‐MHC database and the literature showed that 2 of 64 alleles were only detected in CrAl, including BoLA‐DRB3*029:01 previously reported in African cattle and *048:01 detected in Philippine cattle. Two additional alleles, BoLA‐DRB3*007:02 and *029:02, were only present in CrAl and Lowland Creole cattle. Principal Component Analysis (PCA) showed that Bolivian Creole cattle breeds were closely located but they were distant from the Colombian Hartón del Valle Creole. FST analysis showed a low degree of genetic differentiation between Highland and Lowland Bolivian Creole cattle (FST = 0.015). The present results contribute to increasing our knowledge of BoLA‐DRB3 genetic diversity in cattle breeds.
Indium thiospinels (AIn2S4, A= transition metals) have attracted significant attention due to their potential for manipulating magnetic and optoelectronic properties through changes in chemical ...composition. Defined in the cubic space group Fd-3 m (No. 227), the crystal structure consists of a framework of edge-sharing InS6 octahedra (Oh symmetry), with A cations coordinated tetrahedrally (Td symmetry) to sulfur. In this study, we describe a rapid high-pressure synthetic method (3.5 GPa) to prepare MnIn2S4 polycrystalline samples, with tunable degree of inversion (λ) or Mn-In antisite, meaning that some Mn occupy the octahedral sites and some In atoms are located at the tetrahedral positions. We found that λ closely depends on the synthesis temperature. Notably, the refinement of the crystal structure from X-ray diffraction data reveals positive correlations between the inversion degree and different properties such as the band gap, expanding its spectral coverage, and the magnetic behavior, depending on the occupancy rate of the octahedral or tetrahedral sites by the strongly magnetic Mn2+ ions. Whereas the paramagnetic behavior is not affected by the inversion degree, for higher λ values (30%<λ < 38%), achieved at synthesis temperatures as high of 800ºC, the random distribution of Mn2+ ions between Td and Oh sites accounts for a spin-glass state with a clear cusp in the magnetic susceptibility (ac and dc), based on the strong short-range antiferromagnetic interactions.
•Indium thiospinel materials are well-known exhibit semiconducting behavior.•A high-pressure preparation procedure (3.5 GPa) allowed stabilizing MnIn2S4 sulfides.•The crystal structure exhibits variable inversion degrees depending on the synthesis T.•The optical and magnetic properties closely depend on the inversion degree.•The optical gaps can, thus, be tuned within the visible solar spectrum.
A novel nano-Fe sub(3)O sub(4)-MoO sub(3) (Nanocat-Fe-Mo) catalyst was prepared viasimple wet impregnation and characterized by several techniques. The synthesized Nanocat-Fe-Mo was found to be a ...highly active and efficient catalyst in the oxidation of benzyl alcohol and a series of examples of important organic reactions including A3 couplings, hydrogenations and hydrations. The Nanocat-Fe-Mo could be reused and recycled up to 7 times without any significant yield loss.
Compartmentalization of RNA biosynthetic factors into nuclear bodies (NBs) is a ubiquitous feature of eukaryotic cells. How NBs initially assemble and ultimately affect gene expression remains ...unresolved. The histone locus body (HLB) contains factors necessary for replication-coupled histone messenger RNA transcription and processing and associates with histone gene clusters. Using a transgenic assay for ectopic Drosophila HLB assembly, we show that a sequence located between, and transcription from, the divergently transcribed H3-H4 genes nucleates HLB formation and activates other histone genes in the histone gene cluster. In the absence of transcription from the H3-H4 promoter, “proto-HLBs” (containing only a subset of HLB components) form, and the adjacent histone H2a-H2b genes are not expressed. Proto-HLBs also transiently form in mutant embryos with the histone locus deleted. We conclude that HLB assembly occurs through a stepwise process involving stochastic interactions of individual components that localize to a specific sequence in the H3-H4 promoter.
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► The 297 nt bidirectional promoter of the histone H3-H4 genes nucleates HLB formation ► A combination of stochastic and ordered molecular interactions directs HLB assembly ► Transcription from H3-H4 induces HLB maturation and activates the other histone genes ► Histone 3′ end formation factors accumulate in the HLB independent of pre-mRNA signals
Salzler et al. show that a sequence between Drosophila histone H3 and H4 genes, and its transcription, promotes histone locus body (HLB) assembly and histone gene activation. HLB component behavior in the absence of transcription suggests that stochastic molecular interactions and sequence-dependent stepwise component assembly contribute to HLB formation.
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