Effect of jig constraint state during welding process on fatigue properties of Al/CFRP dissimilar welds and fatigue life evaluation based on singular stress

Manufacturers have been promoting multimaterial designs. So the dissimilar material welding methods are being developed. Especially, heat welding technology, which is a direct joining by local heating, has been focussed. Therefore, this study used a heat welding technology for friction stir spot welding of aluminium alloy and carbon fibre‐reinforced plastic. This study investigated the effect of changes to jig constraint of joined members on the fatigue properties of joints. Also, the fatigue life estimation was carried out by considering the singular stress at the welding joint interface. As a result, the fatigue strength of joint in a less constrained state is higher than that in a more constrained state. The singular stress intensity at the slit tip was uniformly predicted by the differences in welding parameters of joints.     

Development of a biochip with serially connected pneumatic balloons for cell-stretching culture

The stretch stimulus is one of the most important mechanical stimuli sensed by cells. In the present study, a simple microdevice was developed to study the effects of the application of different strain magnitudes to cells. The pressure drop effect in a microchannel was utilized to generate a wide range of strain magnitudes in a single device. The microdevice consisted of 2 layers of polydimethylsiloxane (PDMS), and no alignment process was needed to fabricate it. Eight serially connected balloon structures were included in the device. Cells cultured on the surface of the balloons were stretched by inflating the balloons pneumatically. Finite element analysis (FEA) revealed that 8 different balloons in a single device could generate strains of 14.3-7.7% when air pressure was applied at 50 kPa to the air inlet. Cell culture experiments confirmed the useful application of a wide range of strain magnitudes to cells cultured on balloons inflated to different degrees. The new microdevice utilizing the pressure drop effect is a convenient instrument for the study of cellular mechanotransduction.     

Role of the Innate Immunity Signaling Pathway in the Pathogenesis of Sjögren’s Syndrome

Sjögren’s syndrome (SS) is a systemic autoimmune disease characterized by chronic inflammation of the salivary and lacrimal glands and extra-glandular lesions. Adaptive immune response including T- and B-cell activation contributes to the development of SS. However, its pathogenesis has not yet been elucidated. In addition, several patients with SS present with the type I interferon (IFN) signature, which is the upregulation of the IFN-stimulated genes induced by type I IFN. Thus, innate immune responses including type I IFN activity are associated with SS pathogenesis. Recent studies have revealed the presence of activation pattern recognition receptors (PRRs) including Toll-like receptors, RNA sensor retinoic acid-inducible gene I and melanoma differentiation-associated gene 5, and inflammasomes in infiltrating and epithelial cells of the salivary glands among patients with SS. In addition, the activation of PRRs via the downstream pathway such as the type I IFN signature and nuclear factor kappa B can directly cause organ inflammation, and it is correlated with the activation of adaptive immune responses. Therefore, this study assessed the role of the innate immune signal pathway in the development of inflammation and immune abnormalities in SS.     

Terminally cross-linking polyrotaxane hydrogels applicable for cellular microenvironments

Polyrotaxanes, composed of multiple cyclic molecules threaded onto a polymer chain axis capped with bulky molecules, exhibit unique structural features wherein cyclic molecules can move along a chain. We have previously constructed biointerfaces that utilize the molecular mobility of polyrotaxanes for controlling cellular responses. To implement the features in a three-dimensionally engineered cellular microenvironment, this study developed supramolecular hydrogels using polyrotaxane cross-linkers capped with 4-vinylbenzyl groups at the terminals of a polymer chain axis, where the 4-vinylbenzyl groups in the polyrotaxane allow polymerization with other polyrotaxanes to form polyrotaxane networks. Polyrotaxane hydrogels are successfully prepared without any additional monomers via redox polymerization. The dynamic viscoelasticity and swellability of the hydrogels can be varied depending on the concentration of the polyrotaxanes. When fibroblasts are cultured on hydrogels, sufficient adhesion for cultivation is observed. Therefore, polyrotaxane hydrogels demonstrate suitable potential as new supramolecular biomaterials with dynamic structural features.     

Preparation of a novel (polymer/inorganic nanofiber) composite through surface modification of natural aluminosilicate nanofiber

Imogolite is one of the aluminosilicates with a chemical formula of Al 2 O 3 SiO 2 (H 2 O) n , consisting of hollow nanotubes with an external diameter of about 2.5 nm and a length from several hundred nanometers to a micrometer. Atomic force microscopic (AFM) observation revealed that the imogolite molecules form a fibrous network at pH=3.0. Since the outer surface of imogolite consists of the Al-OH group, a strong interaction can be expected between the Al-OH and the -PO(OH) 2 groups. Octadecylphosphonic acid (OPA) was chosen as a model amphiphilic molecule, and it chemisorbed onto the surface of imogolite. Surface coverage of imogolite with OPA was confirmed by infrared spectroscopy, thermogravimetric analysis, and adhesion force measurement by (AFM). The OPA-chemisorbed imogolite was dispersed in hexane whereas it forms precipitates in water. Since imogolite engages in a specific interaction with -PO(OH) 2 groups, it is expected that imogolite can be molecularly dispersed in -PO(OH) 2 group-modified poly(vinyl alcohol) (PVA). Temperature dependence of dynamic viscoelasticity exhibited a higher temperature shift of the α a -absorption of the matrix phosphorylated PVA for the (imogolite/phosphorylated PVA) hybrid compared with that for phosphorylated PVA.     

Thermodynamic studies on the helix-sense inversion of polyaspartates in the solid state

The Clapeyron analysis has been performed on polyaspartate samples (–[NH–CH(CH₂C(O)OX)C(O)]_n–) carrying side chains such as X = benzyl (1PLA), phenethyl (2PLA), phenylpropyl (3PLA), and phenoxyethyl (PPOLA). In all cases examined, the unwinding and rewinding process of the helical backbone is consistent with the zippering mechanism previously elucidated for the concentrated LC solution. Variation of the PVT properties such as the volume and enthalpy changes at the transition was carefully examined. In the bulk solid state, contribution from the thermodynamic quantities associated with the redistribution of molecules in the configurational space (molecular packing) becomes substantial. It has been concluded that the characteristic features of the ?-α|?-ω transition of 1PLA (140 °C) are inconsistent with the Clapeyron concept, suggesting that the phase transition may involve a non-equilibrium step. The r-α|?-ω transitions of the other polymers were found to conform to the Clapeyron relation. The screw-sense inversion seems to be reversible only when the crystalline structure (hexagonal) remains unaltered before and after the transition. The purpose of this work is to elucidate the key factor responsible for the reversibility of the solid-sate transition, thus providing a basis to understand the role of flanking side chains.     

Is the C-C Motif Ligand 2–C-C Chemokine Receptor 2 Axis a Promising Target for Cancer Therapy and Diagnosis?

C-C motif ligand 2 (CCL2) was originally reported as a chemical mediator attracting mononuclear cells to inflammatory tissue. Many studies have reported that CCL2 can directly activate cancer cells through a variety of mechanisms. CCL2 can also promote cancer progression indirectly through increasing the recruitment of tumor-associated macrophages into the tumor microenvironment. The role of CCL2 in cancer progression has gradually been understood, and various preclinical cancer models elucidate that CCL2 and its receptor C-C chemokine receptor 2 (CCR2) are attractive targets for intervention in cancer development. However, clinically available drugs that regulate the CCL2–CCR2 axis as anticancer agents are not available at this time. The complete elucidation of not only the oncological but also the physiological functions of the CCL2–CCR2 axis is required for achieving a satisfactory effect of the CCL2–CCR2 axis-targeted therapy.     

Investigation of potential profile in electrolyte membrane of PEFC by using microprobe technique

Potential profile in PEFC electrolyte membrane has been investigated by using microprobe technique in order to help understand membrane degradation mechanism. In particular, potential distribution in the membrane under several operation conditions has been measured by using microprobes inserted in the membrane. A theoretical model has been developed to predict the potential distribution under different cell current density with cells of different rib/channel width. The model showed good agreement with experimental result.     

Potential of a direct contact adsorption heat pump system for generating steam from waste water

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p‐T‐x equilibrium curve. To generate steam above 150°C from low‐energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.     

Topology optimization for thermal stress reduction in power semiconductor module

Structural and Multidisciplinary Optimization - The present paper deals with the design of a power semiconductor module using topology optimization. The module must be capable of efficient heat...