► A new approach to designing periodic microstructures of cellular materials. ► Cellular materials with maximum bulk or shear modulus. ► Some interesting topological patterns have been found.
This ...paper presents a new approach to designing periodic microstructures of cellular materials. The method is based on the bidirectional evolutionary structural optimization (BESO) technique. The optimization problem is formulated as finding a micro-structural topology with the maximum bulk or shear modulus under a prescribed volume constraint. Using the homogenization theory and finite element analysis within a periodic base cell (PBC), elemental sensitivity numbers are established for gradually removing and adding elements in PBC. Numerical examples in 2D and 3D demonstrate the effectiveness of the proposed method for achieving convergent microstructures of cellular materials with maximum bulk or shear modulus. Some interesting topological patterns have been found for guiding the cellular material design.
Our understanding of when and how humans adapted to living on the Tibetan Plateau at altitudes above 2000 to 3000 meters has been constrained by a paucity of archaeological data. Here we report data ...sets from the northeastern Tibetan Plateau indicating that the first villages were established only by 5200 calendar years before the present (cal yr B.P.). Using these data, we tested the hypothesis that a novel agropastoral economy facilitated year-round living at higher altitudes since 3600 cal yr B.P. This successful subsistence strategy facilitated the adaptation of farmers-herders to the challenges of global temperature decline during the late Holocene.
There are several well-established techniques for the generation of solid-void optimal topologies such as solid isotropic material with penalization (SIMP) method and evolutionary structural ...optimization (ESO) and its later version bi-directional ESO (BESO) methods. Utilizing the material interpolation scheme, a new BESO method with a penalization parameter is developed in this paper. A number of examples are presented to demonstrate the capabilities of the proposed method for achieving convergent optimal solutions for structures with one or multiple materials. The results show that the optimal designs from the present BESO method are independent on the degree of penalization. The resulted optimal topologies and values of the objective function compare well with those of SIMP method.
Recent development of dense strong‐motion networks and seismic array processing enables rapid tsunami predictions based on the back‐projection (BP) approach. We develop a multi‐array local BP method ...(MLBP) using seismic networks with epicentral distance from 0.7° to 3.5°. The local BPs using individual arrays are first calculated and are then merged into a single image of the rupture process. This multi‐array approach circumvents the issue of artifact in single‐array BP caused by the overlapping of multiple phases and coda waves. Based on the local BP approach, tsunami predictions are available 7 min after the origin time. Case studies of the 2003 Mw 8.1 Tokachi‐oki and the 2011 Mw 9.0 Tohoku earthquakes show that their rupture zones are well resolved and are comparable with principal slip areas inferred from tsunami observations. The amplitude and arrival time errors of the predicted tsunami waves are within −1.59 to 3.74 m and −10.0 to 10.0 min, which are sufficiently small for warning purposes.
Plain Language Summary
Accurate prediction of tsunami waves for residents who are close to the tsunami source requires fast characterization of tsunami‐genic earthquakes. In this research, we develop a tsunami warning approach based on earthquake source observations using multiple dense clusters of seismic stations installed near the coastal region. At a given stage during an earthquake, the recorded seismic wavefield is back‐propagated to retrieve the direction of the seismic source with respect to each cluster of stations. By combining direction information determined at each station group, we retrieve the principle slip fault area that is most responsible for tsunami generation. A simplified earthquake source model is then constructed to predict the tsunami arrival time and height. By adopting local seismic stations within 80–400 km away from the earthquake sources, we show that the tsunami warning can be issued 7 min after the earthquake origin time. Our case studies of the 2003 Mw 8.1 Tokachi‐oki and the 2011 Mw 9.0 Tohoku earthquakes show that our approach adequately reproduces the tsunami observations. The height errors of the predicted tsunami waves are within −1.59 to 3.74 m; the errors of the arrival times are within −10.0 to 10.0 min, which are sufficiently small for warning purposes.
Key Points
We develop a tsunami warning approach based on a multi‐array back‐projection (BP) method using local seismic networks (0.7°<Δ <3.5°)
The multi‐array BP circumvents the issue of artifacts in single‐array BP caused by the overlapping of multiple phases and coda waves
Case studies of the 2003 M8.1 Tokachi and the 2011 M9.0 Tohoku earthquakes demonstrate fast and accurate predictions for tsunami warning
Social impressions arise from characteristics of both perceivers and targets. However, empirical research in the domain of impression formation has yet to quantify the extent to which perceiver and ...target characteristics uniquely contribute to impressions across group boundaries (e.g., race, gender). To what extent does an impression arise from "our mind" versus "a target's face", and does this process differ for impressions across race and gender? We explored this question by estimating intraclass correlation coefficients (ICCs) from cross-classified multilevel models of 188,472 face ratings from 2,230 participants (Study 1) and 219,658 ratings from 2,984 participants (Study 2). We partitioned the total variance in ratings on a trait dimension (trustworthiness, dominance, youthful/attractiveness) into variance explained by perceivers versus targets, and compared these ICCs among different groups (e.g., ratings of own- vs. other-group targets). Overarching results reveal (a) target appearance matters more for women than men, (b) target appearance matters more for impressions on youthful/attractiveness than trustworthiness or dominance dimensions, (c) differences in perceiver/target influences across race did not consistently replicate, and (d) these differences are absent in minimal groups, supporting the role of racial and gender stereotypes in driving these effects. Overall, perceiver characteristics contribute more to impressions than target appearance. Our findings disentangle the contributions of perceiver and targets to impressions and illustrate that the process of impression formation is not equal across various group boundaries.
The diffusion coefficients of several transition elements (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and a few non-transition elements (Mg, Si, Ga, and Ge) in fcc and liquid Al are critically reviewed ...and assessed by means of the least-squares method and semi-empirical correlations. Inconsistent experimental data are identified and ruled out. In the case of the elements, for which plentiful experimental data are available in the literature, the least-squares analysis gives rise to the activation energies and pre-exponential factors in an Arrhenius equation. For the elements with limited experimental data or no data at all, the diffusion parameters are estimated from two semi-empirical correlations. In one correlation, the logarithmic pre-exponential factors are plotted against the activation energies for various elements in Al. In the other correlation, the activation energies are shown as a function of valences relative to Al. The diffusion coefficients calculated by using the evaluated diffusion parameters agree reasonably with the reliable experimental data. The proposed semi-empirical correlations are used to predict the diffusion coefficients of a few elements in liquid Al. A satisfactory agreement between the predicted and measured diffusion coefficients is obtained.
•Nanostructure of spun-on and spray-on PEDOT:PSS thin films is studied.•A correlation is established between the film nanostructure and electrical conductivity.•Effect of process parameters is ...studied on the film characteristics.•A high solution concentration, high process temperature and multiple deposition layers are recommended.
The goal of this paper is to study the characteristics of PEDOT:PSS thin films and the effects of varying the processing parameters on the structure, functionality, and surface wetting of spun-on and spray-on PEDOT:PSS thin films. PEDOT:PSS is a polymer mixture, which is electrically conductive and transparent and, therefore, is an attractive material for some optoelectronic applications, such as organic and perovskite solar cells. In this work, the films are fabricated using spin coating (a lab-scale method) and spray coating (an up-scalable method). The effects of spinning speed, drying time, and post-annealing temperature on spun-on samples and the effects of the substrate temperature and number of spray passes (deposition layers) on spray-on samples, as well as the effect of precursor solution concentration on both cases are investigated. Various characterization tools, such as AFM, SEM, XRD, confocal laser scanning microscopy (CLSM), and electrical conductivity measurements are used to determine the film roughness, thickness, structure, and morphology. The solution precursor physical data, such as contact angle on glass substrates, viscosity, and interfacial tension, are also obtained within a practical range of temperatures and concentrations. It is found that in both spin and spray coating routes, only well-controlled operating conditions result in the formation of conductive and defect-free PEDOT:PSS films. The formation of PEDOT:PSS thin films with small grains composed of PEDOT forming the core of the grains and PSS forming a shell or coating, which are evenly distributed in a PSS-rich matrix, is favored. Conditions leading to the above-mentioned electrically conductive scenario are identified. Other topics, such as the formation of defects and dewetting, are also elucidated.
Mitochondria are highly dynamic and undergo constant fusion and fission that are essential for maintaining physiological functions of cells. Although dysfunction of mitochondria has been implicated ...in tumorigenesis, little is known about the roles of mitochondrial dynamics in metastasis, the major cause of cancer death. In the present study, we found a marked upregulation of mitochondrial fission protein dynamin-related protein 1 (Drp1) expression in human invasive breast carcinoma and metastases to lymph nodes. Compared with non-metastatic breast cancer cells, mitochondria also were more fragmented in metastatic breast cancer cells that express higher levels of total and active Drp1 and less mitochondrial fusion protein 1 (Mfn1). Silencing Drp1 or overexpression of Mfn1 resulted in mitochondria elongation or clusters, respectively, and significantly suppressed metastatic abilities of breast cancer cells. In contrast, silencing Mfn proteins led to mitochondrial fragmentation and enhanced metastatic abilities of breast cancer cells. Interestingly, these manipulations of mitochondrial dynamics altered the subcellular distribution of mitochondria in breast cancer cells. For example, silencing Drp1 or overexpression of Mfn1 inhibited lamellipodia formation, a key step for cancer metastasis, and suppressed chemoattractant-induced recruitment of mitochondria to lamellipodial regions. Conversely, silencing Mfn proteins resulted in more cell spreading and lamellipodia formation, causing accumulation of more mitochondria in lamellipodia regions. More importantly, treatment with a mitochondrial uncoupling agent or adenosine triphosphate synthesis inhibitor reduced lamellipodia formation and decreased breast cancer cell migration and invasion, suggesting a functional importance of mitochondria in breast cancer metastasis. Together, our findings show a new role and mechanism for regulation of cancer cell migration and invasion by mitochondrial dynamics. Thus targeting dysregulated Drp1-dependent mitochondrial fission may provide a novel strategy for suppressing breast cancer metastasis.
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