Crack-Resistance Behavior of an Encapsulated, Healing Agent Embedded Buffer Layer on Self-Healing Thermal Barrier Coatings

In this work, a novel thermal barrier coating (TBC) system is proposed that embeds silicon particles in coating as a crack-healing agent. The healing agent is encapsulated to avoid unintended reactions and premature oxidation. Thermal durability of the developed TBCs is evaluated through cyclic thermal fatigue and jet engine thermal shock tests. Moreover, artificial cracks are introduced into the buffer layer’s cross section using a microhardness indentation method. Then, the indented TBC specimens are subject to heat treatment to investigate their crack-resisting behavior in detail. The TBC specimens with the embedded healing agents exhibit a relatively better thermal fatigue resistance than the conventional TBCs. The encapsulated healing agent protects rapid large crack openings under thermal shock conditions. Different crack-resisting behaviors and mechanisms are proposed depending on the embedding healing agents

Crack-Growth Behavior in Thermal Barrier Coatings with Cyclic Thermal Exposure

Crack-growth behavior in yttria-stabilized zirconia-based thermal barrier coatings (TBCs) is investigated through a cyclic thermal fatigue (CTF) test to understand TBCs’ failure mechanisms. Initial cracks were introduced on the coatings’ top surface and cross section using the micro-indentation technique. The results show that crack length in the surface-cracked TBCs grew parabolically with the number of cycles in the CTF test. Failure in the surface-cracked TBC was dependent on the initial crack length formed with different loading levels, suggesting the existence of a threshold surface crack length. For the cross section, the horizontal crack length increased in a similar manner as observed in the surface. By contrast, in the vertical direction, the crack did not grow very much with CTF testing. An analytical model is proposed to explain the experimentally-observed crack-growth behavior

GM-CSF Promotes the Expansion and Differentiation of Cord Blood Myeloid-Derived Suppressor Cells, Which Attenuate Xenogeneic Graft-vs.-Host Disease

Myeloid-derived suppressor cells (MDSCs) are increased in tumor patients. Studies have shown generation of MDSCs from human peripheral blood mononuclear cells (PBMCs) by various cytokine combinations. However, large scale expansion of human MDSCs has not been demonstrated or applied in clinic settings. We investigated which cytokine combinations among GM-CSF/SCF, G-CSF/SCF, or M-CSF/SCF efficiently expand and differentiate human MDSCs following culture CD34+ cells of umbilical cord blood (CB). GM-CSF/SCF showed the greatest expansion of MDSCs. Up to 108 MDSCs (HLA-DRlowCD11b+CD33+) could be produced from 1 unit of CB following 6 weeks of continuous culture. MDSCs produced from culture of CD34+ cells with GM-CSF/SCF for 6 weeks had the greatest suppressive function of T cell proliferation and had the highest expression of immunosuppressive molecules including iNOS, arginase 1 and IDO compared to those differentiated with G-CSF/SCF or M-CSF/SCF. MDSCs secreted IL-10, TGB-β, and VEGF. The infusion of expanded MDSCs significantly prolonged the survival and decreased the GVHD score in a NSG xenogeneic model of GVHD. Injected MDSCs increased IL-10 and TGF-β but decreased the level of TNF-α and IL-6 in the serum of treated mice. Notably, FoxP3 expressing regulatory T (Treg) cells were increased while IFN-γ (Th1) and IL-17 (Th17) producing T cells were decreased in the spleen of MDSC treated mice compared to untreated GVHD mice. Our results demonstrate that human MDSCs are generated from CB CD34+ cells using GM-CSF/SCF. These MDSCs exhibited potent immunosuppressive function, suggesting that they are useable as a treatment for inflammatory diseases such as GVHD

Anatomical evaluation of CT-MRI combined femoral model

<p>Abstract</p> <p>Background</p> <p>Both CT and MRI are complementary to each other in that CT can produce a distinct contour of bones, and MRI can show the shape of both ligaments and bones. It will be ideal to build a CT-MRI combined model to take advantage of complementary information of each modality. This study evaluated the accuracy of the combined femoral model in terms of anatomical inspection.</p> <p>Methods</p> <p>Six normal porcine femora (180 ± 10 days, 3 lefts and 3 rights) with ball markers were scanned by CT and MRI. The 3D/3D registration was performed by two methods, i.e. the landmark-based 3 points-to-3 points and the surface matching using the iterative closest point (ICP) algorithm. The matching accuracy of the combined model was evaluated with statistical global deviation and locally measure anatomical contour-based deviation. Statistical analysis to assess any significant difference between accuracies of those two methods was performed using univariate repeated measures ANOVA with the Turkey post hoc test.</p> <p>Results</p> <p>This study revealed that the local 2D contour-based measurement of matching deviation was 0.5 ± 0.3 mm in the femoral condyle, and in the middle femoral shaft. The global 3D contour matching deviation of the landmark-based matching was 1.1 ± 0.3 mm, but local 2D contour deviation through anatomical inspection was much larger as much as 3.0 ± 1.8 mm.</p> <p>Conclusion</p> <p>Even with human-factor derived errors accumulated from segmentation of MRI images, and limited image quality, the matching accuracy of CT-&-MRI combined 3D models was 0.5 ± 0.3 mm in terms of local anatomical inspection.</p

Fracture behavior and thermal durability of lanthanum zirconate-based thermal barrier coatings with buffer layer in thermally graded mechanical fatigue environments

The effects of buffer layer on the fracture behavior and lifetime performance of lanthanum zirconate (La2Zr2O7; LZO)-based thermal barrier coatings (TBCs) were investigated through thermally graded mechanical fatigue (TGMF) tests, which are designed to simulate the operating conditions of rotating parts in gas turbines. To improve the thermal durability of LZO-based TBCs, composite coats consisting of two feedstock powders of LZO and 8 wt% yttria-doped stabilized zirconia (8YSZ) were prepared by mixing different volume ratios (50:50 and 25:75, respectively). The composite coat of 50:50 volume ratio was employed as the top coat, and two types of buffer layers were introduced (25:75 volume ratio in LZO and 8YSZ, and 8YSZ only). These TBC systems were compared with a reference TBC system of 8YSZ. The TGMF tests with a tensile load of 60 MPa were performed for 1000 cycles, at a surface temperature of 1100 °C and a dwell time of 10 min, and then the samples were cooled at room temperature for 10 min in each cycle. For the single-layer TBCs, the composite top coat showed similar results as for the reference TBC system. The triple-layer coating (TLC) showed the best thermal cycle performance among all samples, suggesting that the buffer layer was efficient in improving lifetime performance. Failure modes were different for the TBC systems. Delamination and/or cracks were created at the interface between the bond and top coats or above the interface in the single-layer TBCs, but the TBCs with the buffer layer were delaminated and/or cracked at the interface between the buffer layer and the top coat, independent of buffer layer species. This study allows further understanding of the LZO-based TBC failure mechanisms in operating conditions, especially in combined thermal and mechanical environments, in order to design reliable TBC systems

Funding structures for Build-to-Suit developments in Brazil: advantages and risks

Empreendimentos build-to-suit são aqueles em que o locador desenvolve um imóvel sob medida para o locatário, que o ocupará pelo prazo previsto em contrato. Dadas as peculiaridades desse tipo de contrato no contexto do real estate, o objetivo deste artigo é analisar as diferentes origens de recursos (fontes de funding) e a forma como eles são empregados (estruturas de funding) para desenvolver os empreendimentos, e discutir as vantagens e riscos dessas estruturas de funding do ponto de vista do empreendedor, que também é o locador. De forma a desenvolver este estudo e formatar as estruturas de funding apresentadas, parte-se de uma revisão das\ud práticas atuais do mercado imobiliário brasileiro (através de notícias veiculadas\ud na mídia e de prospectos de negócios realizados), da literatura brasileira sobre o tema e do conhecimento gerado no Grupo de Real Estate da Escola Politécnica da USP. De maneira a verificar a validade legal das soluções, é realizada uma checagem com\ud base na legislação brasileira e nas normas da Comissão de Valores Mobiliários.\ud Considera-se fontes de funding aquelas tratadas (1) como equity: capital próprio do empreendedor, capital de parceiros (e sócios) no empreendimento na forma de dinheiro ou imóveis (notadamente, o terreno onde será construído o empreendimento), ou investimento de Fundo de Investimento Imobiliário (FII); e (2) como dívida: financiamento bancário, securitização dos recebíveis de aluguéis com CRI ou debêntures. As estruturas de funding apresentadas serão combinações dessas fontes. A análise evidencia que estruturas com financiamento por securitização e emissão de CRI são as mais adequadas de forma geral para os negócios, assim como o investimento completo por FII para negócios de maior porte e nos quais o FII é proprietário direto do empreendimento. \ud Palavras-chave: real estate, build-to-suit, locação, funding, project financeBuild-to-suit real estate assets are tailor made developments for the tenant purposes, who occupies and operates the property for the duration agreed. Given the peculiarities of these contracts and the specificities of the property, this article aims at analyzing the sources of capital and how these funds are mixed and structured for the developments. The article discusses the risks and benefits of each of these funding\ud structures assuming the role of developer. In order to do this study and establish the funding structures shown, the research starts with a review of the current practices in Brazilian real estate market (based on press releases and prospects of deals), of local research papers, and will use the knowledge created at the Real Estate Research Group at Escola Politécnica at Universidade de São Paulo. Since it’s necessary to validate\ud the solutions proposed, Brazilian laws and Comissão de Valores Mobiliários (CVM) norms\ud are reviewed. Funding sources considered will be treated as (1) equity: developers own funds, partnership (via capital or real state – mainly land – investment), or Fundo de Investimento Imobiliário (Brazilian investment structure comparable to REITs); or as (2) debt: banks traditional credit lines, securitization of receivables with CRI emissions\ud , and debt bond emissions. The funding structures presented are mixes of these sources. The analysis shows that the structures best suited for this purpose are those with debt by securitization with CRI emissions, along with the complete investment by a FII but only with large emissions and having the FII as the sole owner of the real estate. \ud Keywords: real estate, build-to-suit, rent, funding, project financ

Thermal durability and fracture behavior of layered Yb-Gd-Y-based thermal barrier coatings in thermal cyclic exposure

The effects of structural design on the thermal durability and fracture behavior of Yb-Gd-Y-based thermal barrier coatings (TBCs) were investigated through thermal cyclic exposure tests, such as furnace cyclic thermal fatigue (FCTF) and jet engine thermal shock (JETS) tests. The effects of composition in the bond coat and feedstock purity for the buffer layer on its lifetime performance were also examined. To overcome the drawbacks of Yb-Gd-Y-based material with inferior thermal durability due to poor mechanical properties and low coefficient of thermal expansion, a buffer layer was introduced in the Yb-Gd-Y-based TBC systems. In FCTF tests, the TBCs with the buffer layer showed a longer lifetime performance than those without the buffer layer, showing the longest thermal durability in the TBC with the Co-Ni-based bond coat and the buffer layer of regular purity. In JETS tests, the TBC with the Ni-based bond coat and the buffer layer of high purity showed a sound condition after 2000 cycles, showing better thermal durability for TBC with the Co-Ni-based bond coat rather than that with the Ni-based bond coat in the single layer coating without the buffer layer. The buffer layer effectively enhanced the thermal durability in slow temperature change (in the FCTF test), while the bond-coat composition and the feedstock purity for the buffer layer were found to be important factor to improve the thermal durability of the TBC in fast temperature change (in the JEET test). Finally, these research findings allow us to control the structure, composition, and feedstock purity in TBC system for improving the thermal durability in cyclic thermal environments

Patterned Si thin film electrodes for enhancing structural stability

A patterned film (electrode) with lozenge-shaped Si tiles could be successfully fabricated by masking with an expanded metal foil during film deposition. Its electrochemical properties and structural stability during the charge-discharge process were examined and compared with those of a continuous (conventional) film electrode. The patterned electrode exhibited a remarkably improved cycleability (75% capacity retention after 120 cycles) and an enhanced structural stability compared to the continuous electrode. The good electrochemical performance of the patterned electrode was attributed to the space between Si tiles that acted as a buffer against the volume change of the Si electrode