Effects of Thermodiffusion and Nanoparticles on Convective Instabilities in Binary Nanofluids

In this article, the effects of thermodiffusion of nanoparticles and solute in binary nanofluids and nanoparticles on the convective instabilities of a binary nanofluid is theoretically investigated. Thermodiffusion implies that mass diffusion is induced by thermal gradient, which is the so-called Soret effect. In order to analyze the convective instabilities of a binary nanofluid, a new stability criterion is obtained based on the linear stability theory and new factors g and f are proposed. The results show that the Soret effect of solute makes the binary nanofluids unstable significantly and the convective motion in a binary nanofluid sets in easily as the ratio of Soret coefficient of nanofluid to that of binary basefluid δ₄ increases for δ₄ > ?1. It is also found that with an increase of the volume fraction of nanoparticles, the nanofluid becomes stable, but at or near ψ _bf = ? 0.3 the state of nanofluid changes from stable to unstable. The results from the addition factor analysis show that an asymptotic point of ψ _bf where the maximum value of g diverges infinitely exists in the range of ? 1.2 < ψ _bf < ? 1.1 with given conditions. The binary addition factor g is always higher than the normal addition factor f, which means that the heat transfer enhancement by the Soret effect in binary nanofluids is more significant than that in normal nanofluids.     

Quantile Autoregression for Censored Data

Quantile autoregression (QAR) is particularly attractive for censored data. However, unlike the standard regression models, the autoregressive models must take account of censoring on both response and regressors. In this article, we show that the existing censored quantile regression methods produce consistent estimators for QAR models when using only the fully observed regressors. A new algorithm is proposed to provide a censored QAR estimator by adopting imputation methods. The algorithm redistributes probability mass of censored points appropriately and iterates towards self‐consistent solutions. Monte Carlo simulations and empirical applications are conducted to demonstrate merits of the proposed method.     

Phytochemical stability in dried apple and green tea functional products as related to moisture properties

In this study, apple products made with and without added green tea extract were freeze-dried and stored for up to 45 days at 30 °C in low and intermediate moisture environments (water activity, a_w, 0.11, 0.22, 0.32, 0.57, and 0.75). Kinetic models were developed for the changes in color and decreases in contents of selected green tea and apple monomeric and polymeric flavanols and ascorbic acid. Moisture isotherms were developed for each product. At various moisture levels, the glass transition temperature (T_g) was measured by DSC and water mobility by ¹H NMR. Chemical changes were related to T_g, a_w, and water mobility in the products.Phytochemical degradation occurred more rapidly at higher moisture contents, except for caffeine which was stable. In the product containing apple with green tea, the content of monomeric flavan-3-ols decreased by 34% and 39% after 45 days of storage at a_w of 0.56 and 0.75, respectively. Phytochemical degradation correlated with increasing a_w, T_g, and water mobility. This study showed that, in general, storage at a_w 0.75 most affected phytochemical stability and color.     

Injection molding with an additive manufactured tool

This study examines the viability of using additively manufactured injection molding tools for short run proof‐of‐concept plastic parts by assessing the quantity and quality of molded parts. Prototyping injection molded parts traditionally can be very expensive, but with improved additive manufacturing materials and techniques such costs could be reduced. To prove this, plastic tools were made by using PolyJet and Fused Deposition Modeling out of Digital ABS, FullCure 720, and ULTEM 1010 materials in this study. The test tools were then compared to the standard P20 metal tool by molding acetal, polycarbonate (PC), and polypropylene (PP) in each tool type. The molded parts were analyzed for processing effects on part shrink, physical, and mechanical properties. Testing concluded that parts molded with additively manufactured tools performed comparably to parts made on a P20 tool. However, the quantity of satisfactory parts molded in acetal and PC were consistent with the literature at 10–100 parts. Conversely, molding in PP suggested that processing with additive manufactured tools could exceed 250 parts. POLYM. ENG. SCI., 59:1911–1918, 2019. © 2019 Society of Plastics Engineers     

Does rapid adaptation to a poor-quality host by Callosobruchus maculatus (F.) cause cross-adaptation to other legume hosts?

Initial assays indicated that lentil is a very poor host for an Asian population of the seed beetle Callosobruchus maculatus (F.). Larval survival was near zero, and females laid few or no eggs on lentil seeds. However, mass selection in the laboratory consistently produced a rapid increase in survival (from <2% to >80% in <20 generations) as well as a moderate increase in host acceptance. We investigated whether adaptation to lentil simultaneously causes cross-adaptation to other grain legumes, particularly those closely related to lentil. After 30 generations of selection, survival in lentil exceeded 90% in the lentil line, but remained near zero in a line maintained on the ancestral host, mung bean. Despite this extreme divergence in performance in lentil, the lines did not differ in their survival on eight other legume hosts, including two hosts (pea and fava bean) that belong to the same tribe (Vicieae) as lentil. Similarly, females from the lentil line laid more than three times as many eggs on lentil as females from the mung bean line did, but the lines exhibited only minor differences in their acceptance of eight alternative hosts. Lentil-line females did not show greater acceptance of artificial seeds (glass balls), as might be expected if increased egg-laying on lentil was simply due to a reduction in the overall threshold for oviposition. We conclude that the changes in larval physiology and adult behavior that permitted rapid colonization of a marginal host were largely specific to that host, and not likely to promote a further expansion of the beetle's host range.     

Transient model of oxygen-starved proton exchange membrane fuel cell for predicting voltages and hydrogen emissions

Transfer (crossover) leaks initiated by the chemical deterioration of the PEM and the resulting performance degradation has been previously identified as one the primary life-limiting factors in fuel cells. The leaks result in reduced oxygen levels in affected cells, where a secondary factor intimately related to this is high hydrogen emissions in the cathode exhaust when some cells operate in fully-oxygen-starved conditions. This paper builds on previous work that developed a unified fuel cell model that predicts cell voltage behavior under driving (normal) and driven (oxygen-starved) conditions, where this latest analysis now explicitly includes hydrogen pumping and emissions release when operating under oxygen-depleted conditions. In addition to considering diffusion effects and electrochemical effects, the model tracks the evolution of hydrogen in the cell cathode when no oxygen remains to generate water. The voltage response of the model under normal (non-starved) conditions is first validated for steady-state and transient (current step-change) conditions against previously published experiments, and then the model is used to simulate the cell voltage and stack hydrogen emissions behavior measured from three different commercially available fuel cell stacks. In the first fuel cell stack, a 9-cell commercial short stack, only one cell was fully oxygen-starved. Excellent agreement is seen between the measured and simulated hydrogen release concentrations (where air injection was used downstream of the stack to ensure adequate oxygen levels for measurement with a catalytic hydrogen sensor and to condense water vapor in the exhaust), where the role of hydrogen pumping is seen to contribute significantly to the release behavior. The first fuel cell stack is then used transiently in comparison with testing performed where the hydrogen injection level in the cell is changed quickly, where the model gives good agreement with the measured emission response and cell voltage behavior. Further comparisons with test data from a second and third 10-cell commercial short stack models operated with stack inlet hydrogen injection show good agreement with measured emissions onset versus current, where the observed threshold of starvation and emissions occurs a few percent sooner in the third model than the simulation, but the overall behavior is well predicted.     

基于文献可视化的体感交互智能健身研究分析和展望

目的 从疫情期间居家健身热潮出发,结合智能、医疗、体育、健康相关政策背景,了解基于体感交互及其相关技术的智能健身相关研究现状与发展趋势。方法 以Cnki数据库和Web of science数据库作为数据来源,使用科学计量方法,运用Citespace以及VOSviewer文献数据可视化分析软件进行     

Comparison of Macrophage Immune Responses and Metabolic Reprogramming in Smooth and Rough Variant Infections of Mycobacterium mucogenicum

Mycobacterium mucogenicum (Mmuc), a rapidly growing nontuberculous mycobacterium (NTM), can infect humans (posttraumatic wound infections and catheter-related sepsis). Similar to other NTM species, Mmuc exhibits colony morphologies of rough (Mmuc-R) and smooth (Mmuc-S) types. Although there are several case reports on Mmuc infection, no experimental evidence supports that the R-type is more virulent. In addition, the immune response and metabolic reprogramming of Mmuc have not been studied on the basis of morphological characteristics. Thus, a standard ATCC Mmuc strain and two clinical strains were analyzed, and macrophages were generated from mouse bone marrow. Cytokines and cell death were measured by ELISA and FACS, respectively. Mitochondrial respiration and glycolytic changes were measured by XF seahorse. Higher numbers of intracellular bacteria were found in Mmuc-R-infected macrophages than in Mmuc-S-infected macrophages. Additionally, Mmuc-R induced higher levels of the cytokines TNF-α, IL-6, IL-12p40, and IL-10 and induced more BMDM necrotic death. Furthermore, our metabolic data showed marked glycolytic and respiratory differences between the control and each type of Mmuc infection, and changes in these parameters significantly promoted glucose metabolism, extracellular acidification, and oxygen consumption in BMDMs. In conclusion, at least in the strains we tested, Mmuc-R is more virulent, induces a stronger immune response, and shifts bioenergetic metabolism more extensively than the S-type. This study is the first to report differential immune responses and metabolic reprogramming after Mmuc infection and might provide a fundamental basis for additional studies on Mmuc pathogenesis.     

Intrinsic 3D Prestressing: A New Route for Increasing Strength and Improving Toughness of Hybrid Inorganic Biocements

Cement is the most consumed resource and is the most widely used material globally. The ability to extrinsically prestress cementitious materials with tendons usually made from steel allows the creation of high‐strength bridges and floors from this otherwise brittle material. Here, a dual setting cement system based on the combination of hydraulic cement powder with an aqueous silk fibroin solution that intrinsically generates a 3D prestressing during setting, dramatically toughening the cement to the point it can be cut with scissors, is reported. Changes of both ionic concentration and pH during cement setting are shown to create an interpenetrating silk fibroin inorganic composite with the combined properties of the elastic polymer and the rigid cement. These hybrid cements are self‐densifying and show typical ductile fracture behavior when dry and a high elasticity under wet conditions with mechanical properties (bending and compressive strength) nearly an order of magnitude higher than the fibroin‐free cement reference.     

Can Mean‐Curvature Flow be Modified to be Non‐singular?

This work considers the question of whether mean‐curvature flow can be modified to avoid the formation of singularities. We analyze the finite‐elements discretization and demonstrate why the original flow can result in numerical instability due to division by zero. We propose a variation on the flow that removes the numerical instability in the discretization and show that this modification results in a simpler expression for both the discretized and continuous formulations. We discuss the properties of the modified flow and present empirical evidence that not only does it define a stable surface evolution for genus‐zero surfaces, but that the evolution converges to a conformal parameterization of the surface onto the sphere.