Light-Weight and Flexible High-Entropy Alloys

The lightweight and flexible materials can improve people’s quality of daily life; in addition, the materials can be widely used in aerospace, automotive, consumer electronics, etc. Recently, high-entropy alloys had become hot issues in materials science with many excellent properties; therefore, we can combine the design ideas of high-entropy alloys with lightweight materials and flexible materials, taking into account the advantages of two types of materials, and promoting the development and progress of new materials. In the chapter, we will elaborate on the relationship between the microstructure and properties of lightweight high-entropy alloys and the design ideas of high-entropy alloys with flexible materials that were investigated in recent years. Furthermore, as the microstructure and mechanical properties of the alloys exhibit the nonlinear behaviors with entropy on high-entropy alloys, we would like to define the lightweight high-entropy alloy as the density is lower than 6 g/cm3, the mix-entropy of these alloys is higher than 1R (here, R is gas constant), and the number of components is four or more. Finally, it is expected to broaden the research field of high-entropy alloys and provide some new directions for the development of new materials

Bid Optimization by Multivariable Control in Display Advertising

Real-Time Bidding (RTB) is an important paradigm in display advertising, where advertisers utilize extended information and algorithms served by Demand Side Platforms (DSPs) to improve advertising performance. A common problem for DSPs is to help advertisers gain as much value as possible with budget constraints. However, advertisers would routinely add certain key performance indicator (KPI) constraints that the advertising campaign must meet due to practical reasons. In this paper, we study the common case where advertisers aim to maximize the quantity of conversions, and set cost-per-click (CPC) as a KPI constraint. We convert such a problem into a linear programming problem and leverage the primal-dual method to derive the optimal bidding strategy. To address the applicability issue, we propose a feedback control-based solution and devise the multivariable control system. The empirical study based on real-word data from Taobao.com verifies the effectiveness and superiority of our approach compared with the state of the art in the industry practices

Propofol affects the biological behavior of ovarian cancer SKOV3 cells via ERK1/2-MMP-2/9 signaling pathway

Purpose: To investigate the effect of propofol on the biological behavior of ovarian cancer SKOV3 cells, and the mechanism of action involved. Methods: SKOV3 cells cultured in vitro were randomly divided into control group, fat emulsion group, low-dose propofol group (LDPG, 25 μmol/L), medium-dose propofol group (MDPG) (50 μmol/L) and high-dose propofol group (HDPG) (100 μmol/L). Apoptosis was determined by flow cytometry, while Transwell assay was used to measure the migration and invasion abilities of the cells. The protein levels of ERK1/2, MMP-2, MMP-9 were assayed with Western blotting. Moreover, the cells were transfected with siERK, and the regulatory effect of propofol on ERK1/2-MMP-2/9 signaling pathway was determined. Results: Apoptosis in HDPG was significantly reduced, relative to MDPG, while migration and invasion were enhanced, relative to MDPG (p < 0.05). Moreover, MMP-2, ERK1/2, and MMP-9 proteins were significantly higher in MDPG and HDPG than in control, fat emulsion and LDPGs (p < 0.05), and were upregulated in HDPGs, relative to MDPG (p < 0.05). In contrast, propofol did not up-regulate these proteins in siRNA-treated cells. Conclusion: Propofol enhances the migration, proliferation, and invasive ability SKOV3 cells, and upregulates the expressions of MMP-2, ERK1/2, and MMP-9 in these cells, via a mechanism related to the activation of ERK1/2-MMP-2/9 signaling route. These properties provide novel leads for the development of new drugs for ovarian cancer Keywords: Propofol, ERK1/2-MMP-2/9 signal route, Ovarian cancer, Biological behavio

Sorption behaviour of per- and polyfluoroalkyl substances (PFASs) in tropical soils

The sorption behaviour of three perfluoroalkyl substances (PFASs), namely perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS), was determined on 28 tropical soils. Tropical soils are often highly weathered, richer in sesquioxides than temperate soils and may contain variable charge minerals. There are little data on sorption of PFASs in tropical soils. The highest Kd values were found for PFOS with mean values ranging from 0 to 31.6 L/kg. The Kd values for PFOA and PFHxS ranged from 0 to 4.9 L/kg and from 0 to 5.6 L/kg, respectively. While these values are in the range of literature sorption data, the average Kd values for PFOS and PFOA from the literature were 3.7 times and 3.6 times higher, respectively, than those measured in this study. Stepwise regression analysis did explain some of the variance, but with different explanatory variables for the different PFASs. The main soil properties explaining sorption for PFOS and PFOA were oxalate-extractable Al and pH, and for PFHxS was pH

Measuring Shear-Induced Adhesion of Gecko-Inspired Fibrillar Arrays Using Scanning Probe Techniques

The natural ability of geckos and spiders to climb almost all surfaces using the compliant, nano‐structured components on their feet provides motivation for making bio‐inspired adhesives. The goal of the studies in this paper is to create an analytical technique for improving the ability to characterize dry adhesives modeled after these biological systems. The technique described herein uses a scanning probe microscope to manipulate a flat test surface in contact with biomimetic fibrillar arrays while monitoring the adhesion forces. Adhesion forces were measured after both normal contact and shear‐induced contact between the nano‐structured fibrils and the test surface. Results confirm that the adhesion forces are higher for bio‐inspired adhesives after a shear‐induced contact. Variations in these forces can be measured across the sample with micrometer‐scale lateral resolution. This method of analysis can be extended to evaluate bio‐inspired dry adhesives with realistic mechanisms of attachment utilized in robotic and similar applications of these materials

Harnessing Tunable Scanning Probe Techniques to Measure Shear Enhanced Adhesion of Gecko-Inspired Fibrillar Arrays

The hierarchical arrays of mesoscale to nanoscale fibrillar structures on a gecko’s foot enable the animal to climb surfaces of varying roughness. Adhesion force between the fibrillar structures and various surfaces is maximized after the gecko drags its foot in one direction, which has also been demonstrated to improve the adhesion forces of artificial fibrillar arrays. Essential conditions that influence the magnitude of these interactions include the lateral distance traveled and velocity between the contacting surfaces, as well as the velocity at which the two surfaces are subsequently separated. These parameters have, however, not been systematically investigated to assess the adhesion properties of artificial adhesives. We introduce a systematic study that investigates these conditions using a scanning probe microscope to measure the adhesion forces of artificial adhesives through a process that mimics the mechanism by which a gecko climbs. The measured adhesion response was different for arrays of shorter and longer fibrils. These results from 9000 independent measurements also provide further insight into the dynamics of the interactions between fibrillar arrays and contacting surfaces. These studies establish scanning probe microscopy techniques as a versatile approach for measuring a variety of adhesion properties of artificial fibrillar adhesives

Developing the Symptoms and Functional Impairment Rating Scale:A Multi-Dimensional ADHD Scale

Objective: This research developed a practical, multi-dimensional attention deficit hyperactivity disorder (ADHD) rating scale (i.e., the Symptoms and Functional Impairment Rating Scale, SFIRS) for Chinese children, aged 6-12 years, with ADHD. Methods: The structural validity, criterion validity, internal consistency, and test-retest reliability of the scale were evaluated. Item screening was conducted with 412 ADHD patients and 322 developmentally typical controls. Results: The scale includes 44 items, divided among Hyperactivity-Impulsivity, Self-Control, Inattention, Self-Management, Academic Performance, and Social Interaction. The six-factor model showed good data fit, with each factor significantly correlated with its corresponding criterion (r=0.690-0.841). The Cronbach's α of the full scale was 0.976. Total score test-retest reliability was r=0.816 (p<0.01). Conclusion: The SFIRS thus demonstrated good reliability and validity and may be used to assess ADHD among children aged 6-12 years in China

The role of surface charge and pH changes in tropical soils on sorption behaviour of per- and polyfluoroalkyl substances (PFASs)

Crown Copyright © 2019 Published by Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (April 2019) in accordance with the publisher’s archiving policyThis study investigated the effect of surface charge on the sorption of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) onto 7 tropical soils as a function of pH. The net surface charge became less negative with decreasing pH (from 7.5 to 3.5) in all soils. The rate of change in net surface charge varied from −0.6 to −2.8 (cmol/kg)/pH unit. The effect on sorption behaviour of PFASs was variable among soils. For two soils, the average sorption increased 54- and 45-fold for PFOS, 33- and 9-fold for PFOA, and 39- and 400-fold for PFHxS, across the pH range 7.5 to 3.5. Sorption in another sandier soil showed negligible change with decreasing pH. Sorption in the other soils did not change significantly until the pH decreased to approximately 5.5. The soils with high contents of sesquioxides (Fe and Al oxides) showed the most marked increase in sorption with decreasing pH. This study demonstrated that in addition to hydrophobic interactions with OC and other processes, electrostatic interactions are also important in the sorption process for these chemicals in soils. In acidic, variably charged tropical soils there is the possibility that any PFOS, PFOA or PFHxS sorbed to the soils may become desorbed if management practices (e.g. liming) raised soil pH

Preliminary development of a bio-inspired hexapod climbing robot relying on dry adhesives

Biologists have recently discovered that dry adhesion on the feet of geckos and hunting spiders provides remarkable adhesive forces generated by van der Waals forces. Different researches have attempted to mimic the adhesive used by geckos and spiders adhesives through novel manufacturing processes. This thesis presents the preliminary analysis and development of hexapod climbing robot prototypes designed to take advantage of the special features that dry adhesion offers. A kinematic analysis was performed, which was validated through an experimental procedure. The two robotic prototypes, which were developed following engineering design procedures, are presented and discussed in this thesis. Preliminary investigations on optimal trajectory and joint torques for enhancing dry adhesive properties are introduced for a future in depth analysis and use in climbing platforms

Improved Bio-inspired Artificial Gecko Adhesive by Using Hierarchical Fibrillar Structures

Geckos are well known for being rapid climbers that have long existed in nature. The reversible and reusable adhesive on their feet intrigues scientists to explore a bio-mimetic adhesive, which inherits the adhesion properties of the gecko’s adhesives. Recent advances in electron microscopy reveal the secret of gecko’s climbing ability: there are hierarchical fibrillar structures branching from the skin of their climbing feet. Sizes of these hierarchical fibrils range from micrometer to nanometer. These fibrils are arranged to closely resemble a tree, and these tree like structures form a fibril forest on the skin of the climbing feet. Nano-fibrils in close proximity with the contacting surfaces interact with the substrate through intermolecular forces. Slender micro-fibrils extend the nano-fibrils, which are located at their open ends, to reach recesses of the contacting surfaces. The special arrangement of the fibrillar arrays enables quick attachment and detachment of the feet from surfaces of different materials and varying roughness. Inspired by the gecko’s adhesive, artificial fibrillar adhesives have been sought developing for more than a decade. Early attempts were focused on making use of the intermolecular interaction by nano-fibrillar arrays. These artificial fibrillar adhesives have achieved great performance on flat surfaces but not as good when they were used on relatively rough surfaces. Recent attempts of preparing a hierarchical fibrillar structure, which contains fibrils in different length scales, have rare success on improving adhesion performance. Evidence of extra compliancy provided by the hierarchical structure is also not clear. This thesis provides evidence that there is a correlation between structure compliancy and adhesion performance of a hierarchical fibrillar adhesive. Improved compliancy and adhesion forces are observed on a hierarchical fibrillar structure with achievements of several milestones, which include developing methods for preparing and characterizing hierarchical fibrillar structures. Experimental results also reveal the interaction of fibrillar arrays with the contacting surfaces. Information obtained is valuable for future development and application of such artificial fibrillar adhesive