Microstructure-Based Modeling of the Effect of Inclusion on the Bendability of Advanced High Strength Dual-Phase Steels

Advanced high strength dual-phase steels are one of the most widely sought-after structural materials for automotive applications. These high strength steels, however, are prone to fracture under bending-dominated manufacturing processes. Experimental observations suggest that the bendability of these steels is sensitive to the presence of subsurface non-metallic inclusions and the inclusions exhibit a rather discrete size effect on the bendability of these steels. Following this, we have carried out a series of microstructure-based finite element calculations of ductile fracture in an advanced high strength dual-phase steel under bending. In the calculations, both the dual-phase microstructure and inclusion are discretely modeled. To gain additional insight, we have also analyzed the effect of an inclusion on the bendability of a single-phase material. In line with the experimental observations, strong inclusion size effect on the bendability of the dual-phase steel naturally emerge in the calculations. Furthermore, supervised machine learning is used to quantify the effects of the multivariable input space associated with the dual-phase microstructure and inclusion on the bendability of the steel. The results of the supervised machine learning are then used to identify the contributions of individual features and isolate critical features that control the bendability of dual-phase steels.

Photophysical Properties of Donor-Acceptor Stenhouse Adducts and Their Inclusion Complexes with Cyclodextrins and Cucurbit[7]uril

Donor-acceptor Stenhouse adducts (DASAs) are a novel class of solvatochromic photoswitches with increasing importance in photochemistry. Known for their reversibility between open triene and closed cyclized states, these push-pull molecules are applicable in a suite of light-controlled applications. Recent works have sought to understand the DASA photoswitching mechanism and reactive state, as DASAs are vulnerable to irreversible “dark switching” in polar protic solvents. Despite the utility of fluorescence spectroscopy for providing information regarding the electronic structure of organic compounds and gaining mechanistic insight, there have been few studies of DASA fluorescence. Herein, we characterize various photophysical properties of two common DASAs based on Meldrum’s acid and dimethylbarbituric acid by fluorescence spectroscopy. This approach is applied in tandem with complexation by cyclodextrins and cucurbiturils to reveal the zwitterionic charge separation of these photoswitches in aqueous solution and the protective nature of supramolecular complexation against degradative dark switching. DASA-M, for example, was found to form a weak host-guest inclusion complex with (2-hydroxypropyl)-γ-cyclodextrin, with a binding constant K = 60 M−1, but a very strong inclusion complex with cucurbit[7]uril, with K = 27,000 M−1. This complexation within the host cavity was found to increase the half-life of both DASAs in aqueous solution, indicating the significant and potentially useful stabilization of these DASAs by host encapsulation.

Extrinsic viscous anisotropy in two-phase aggregates, fabric parametrisation and application to mantle convection

<p>Earth's mantle rocks are poly-aggregates where different mineral phases coexist.  These rocks may often be approximated as two-phase aggregates with a dominant phase and less abundant one (e.g. bridgmanite-ferropericlase aggregates in the lower mantle). Severe shearing of these rocks leads to a non-homogeneous partitioning of the strain between the different phases. The resulting bulk rock is mechanically not isotropic, and the elastic and the viscous tensor depend on the volume fraction and viscosity contrast between the mineral phases and the fabric.</p><p>Here we employ three-dimensional mechanical models to reproduce and parametrise fabrics typical of mantle rocks and quantify the evolution of the viscous tensor. These fabrics are produced by shearing a mechanically heterogeneous medium comprised by randomly distributed isotropic inclusions embedded in: i) a weak inclusion-strong matrix aggregate where strain is mainly accommodated by the weak phase, that flattens and yields a penetrative foliation; and, ii) a strong inclusion-weak matrix where strain is mainly accommodated by the matrix, in this case, the strong phase deforms primarily parallel to the direction of the flow, producing cigar-shaped inclusions.</p><p>Finally, we combine the fabric parametrisation of a two-phase aggregate with the Differential Effective Medium (DEM) theory to study the evolution of the viscous tensor and its effects in mantle dynamics. The results of two-dimensional models of thermal convection show that a viscosity contrast of one order of magnitude between the two mineral phases is enough to deflect mantle plumes and produce convection patterns that differ considerably from the ideal isotropic media.</p>

On the Margins of Citizenship: The Refugee Crisis and the Transformation of Identities in Europe

Drawing on the notion of the “right to have rights”, the study aims to explore how the European responses in the context of the current so called “refugee crisis”, based on strong inclusion-exclusion mechanisms, as well as the current shortcomings of the international human rights regime can be pertinent for analysing and capturing current transformations of the notion and foundations of European citizenship. It is further suggested that the institution of European citizenship in its current form needs to be superseded, in order to attain a truly cosmopolitan content and to provide a basis for a universalistic human rights regime. The main proposal presented in this direction, stresses the need to rethink human rights in terms of political practices and to “rediscover” the revolutionary heritage of human rights from an Arendtian perspective.

Binding of Coumarin 334 withβ-Cyclodextrin and with C-Hexylpyrogallol[4]arene: Opposite Fluorescence Behavior

We report here the structure of the host-guest complexes of Coumarin 334 (C334) withβ-cyclodextrin (β-CD) and with C-hexylpyrogallol[4]arene (C-HPA) and the effect of acidity on the neutral-cation equilibrium of C334 in water and in the presence of the host molecules. The structures of the host-guest complexes are proposed on the basis of the change of fluorescence on the addition ofβ-CD or C-HPA to C334 and by 2D ROESY spectroscopy. Opposite fluorescence behaviors, that is, quenching of fluorescence inβ-CD and enhancement of fluorescence in C-HPA are observed. Time-resolved fluorescence analysis is done for the complexation, and biexponential decay pattern is observed. The possible strong inclusion complexation with C-HPA is explained. The ground and the excited statepKavalues for the protonation equilibrium of C334 in water and the difficulty of protonation in the presence of the host molecules are discussed.

Combinatorial Regulation of Protein 4.1R Exon 16 Alternative Splicing: Modulation of Fox-2 Activated Splicing by Other Intronic and Exonic Motifs.

During erythroid differentiation, stage-specific activation of protein 4.1R exon 16 splicing is critical for the mechanical stability of the erythrocyte plasma membrane. The molecular mechanism of this erythroid splicing switch involves multiple factors including stimulation by Fox proteins acting at splicing enhancers in the proximal downstream intron, and inhibition by hnRNPA1 protein acting at silencer elements in exon 16. To explore how the dynamic interplay among these and other factors can fine tune splicing efficiency, we created a series of exon 16-containing minigenes in which splicing efficiency was measured as a function of variation in exon and intron regulatory elements. In the context of wild type exon 16 with intact hnRNP A1 silencer elements and a weak 5′ splice site, an enhancerless construct with no Fox binding sites exhibited little or no exon 16 inclusion in transfected HeLa cells, and over-expression of Fox-2 did not significantly promote inclusion. Insertion of two wild type UGCAUG elements enhanced splicing substantially in a Fox-2-dependent manner and four elements gave even stronger inclusion. Since another study identified the pentamer GCAUG as the Fox binding site, we tested binding site sequence as a potential source of variation in splicing efficiency. Mutation of the first U residue in UGCAUG yielded weaker, but still Fox-2 dependent, activation of splicing, whereas mutation of the terminal G residue dramatically reduced enhancer activity. To investigate whether enhancer activity of Fox binding sites can be modulated by adjacent sequence motifs, we compared exon 16 splicing efficiency in constructs having Fox sites flanked either by neutral sequence or by an A1 silencer element UAGGG. Introduction of the A1 binding site led to a dramatically reduced enhancer activity including its responsiveness to Fox-2 overexpression. These results indicated that efficiency of splicing of Fox-regulated exons is strongly influenced by the number and sequence of intron enhancer elements and by the presence of adjacent antagonistic elements. In further experiments, we demonstrated that the efficiency of splicing is also strongly dependent on exon 16 and its splice sites. Constructs lacking the major exon 16 silencer element for hnRNP A1 binding exhibited partial exon 16 inclusion in the absence, and very strong inclusion in the presence, of a Fox intron enhancer. Finally, strengthening the weak 5′ splice site of exon 16 abrogated many of these regulatory effects and led to strong inclusion of exon 16 independent of other variables. These findings are consistent with previous data showing antagonism between A1 and Fox in their effects on exon 16 splicing, and suggest that Fox proteins primarily function to overcome the weak 5′ splice site and its repression by hnRNP A1 bound at nearby exonic site(s). We propose that the erythroid alternative splicing program can activate splicing a number of alternative exons with variable efficiency based on each exon’s individual complement of exonic and intronic splicing regulatory elements. Modulation of splicing factor expression, typified by the stage-specific down-regulation of hnRNP A1 during erythroblast differentiation, can further alter splicing efficiency of these exons in a selective, motif-dependent manner. Future experiments with exon microarrays will be aimed at identifying some of the alternative exons that are regulated by that program, and determine its importance to the erythroid differentiation process.