Development of Novel Nanomaterials for High-Performance and Low-Cost Fuel Cell Applications

Proton exchange membrane fuel cells (PEMFCs) are promising energy converting technologies to generate electricity by mainly using hydrogen as a fuel, producing water as the only exhaust. However, short life-time and high cost of Pt catalyst are the main obstacles for the commercialization of PEMFCs. In the conventional carbon black supported platinum nanoparticle (NP) commercial catalyst, carbon supports are prone to oxidation and corrosion over time that results in Pt NPs migration, coalescence, even detaching from the catalyst support. In addition, Ostwald ripening of the Pt NPs could also occur due to their high surface energy and zero dimensional structural features. All these contribute to the degradation of fuel cell performance. This research aims at fabricating various advanced nanomaterials, including (1) Pt-based highly efficient nanocatalysts and (2) alternative nanostructured durable catalyst supports, to address the above-mentioned challenges in PEMFCs. It is well known that the catalytic activity and durability of Pt catalysts are highly dependent on their size and shape. In contrast to commercially-used Pt spherical nanoparticles, one-dimensional (1D) structures of Pt, such as nanowires (NWs), exhibit additional advantages associated with their anisotropy and unique structure. We first reported a new approach to address both activity and durability challenges of PEM fuel cells by using 1D Pt nanowires (PtNWs) as electrocatalyst. Pt NWs were synthesized via a very simple environmentally-friendly aqueous solution route at room temperature, without the need of heating, surfactants or complicated experimental apparatus. This novel PtNW nanostructure showed much improved activity and durability than the state-of-the-art commercial Pt/C catalyst which is made of Pt nanoparticles. Further, Pt NWs were grown on Sn@CNT nanocable support to form a novel 3D fuel-cell electrode (PtNW/Sn@CNT). This approach allows us to combine the advantages of both PtNW catalyst and Sn@CNT 3D nanocable support for fuel cell applications. The PtNW/Sn@CNT 3D electrodes showed greatly enhanced electrocatalytic activities for ORR, MOR and improved CO tolerance than commercial Pt/C nanoparticle catalyst. To save more platinum, ultrathin Pt NWs with even smaller diameters of 2.5 nm (vs. 4 nm reported in our previous work) have been successfully synthesized when using N-doped CNTs as support. Direct evidence for the formation of ultrathin Pt NWs was provided by systematically investigating their growth process under TEM. Nitrogen doping in CNTs played a key role in the formation of ultrathin Pt nanowires. In terms of low durability of PEM fuel cell catalysts, the corrosion of current commonly-used carbon black support materials have been identified to be the major contributor to the catalyst failure. One of the major challenges lies in the development of inexpensive, efficient, and highly durable alternative catalyst supports that possess high corrosion resistance, high conductivity and high surface area. In this work, a series of promising alternative nanostructured catalyst supports, including 0D Nb-doped TiO2 hollow nanospheres, 1D TiSix-NCNT nanostructures, and 2D graphene nanosheets, have been synthesized by various methods and used as catalyst supports. Pt nanoparticles were then deposited on these novel supports, showing enhanced catalytic activities and durabilities. Most interestingly, a new technique, atomic layer deposition (ALD), was used to uniformly deposit Pt nanoparticles, subnanometer clusters and single atoms on graphene nanosheets. Downsizing Pt nanoparticles to clusters or even single atoms could significantly increase their catalytic activity and is therefore highly desirable to maximize the efficiency. In summary, the discoveries in this thesis contribute to applying various novel nanostructured materials to design highly active and stable electrocatalyst and durable catalyst support to develop high performance and low cost PEM fuel cells

Application of Neural-Fuzzy System in Twin-Turbo Hydraulic Torque Converter's Performance Testing

AbstractTwin-turbo hydraulic torque converter's performance testing is very important in the product's development and production. According to the needs of data processing and analysis in performance testing, A neural-fuzzy algorithm was used to analyze the test data in this paper. It can improve computing speed and programming capability, decrease artificial involved times, realize the data analysis processing's automation. The application shows that the digital information's relationship can be expressed very well by this method. At the same time, this method has high degree of accuracy and quick speed on data recognition and can satisfy the requirement of designing

β-Glucan Oligosaccharide Enhances CD8+ T Cells Immune Response Induced by a DNA Vaccine Encoding Hepatitis B Virus Core Antigen

DNA vaccination can induce specific CD8+ T cell immune response, but the response level is low in large mammals and human beings. Coadministration of an adjuvant can optimize protective immunity elicited by a DNA vaccine. In this study, we investigated the effect of a synthetic glucohexaose (β-glu6), an analogue of Lentinan basic unit, on specific CD8+ T cell response induced by a DNA vaccine encoding HBcAg (pB144) in mice. We found that β-glu6 promoted the recruitment and maturation of dendritic cells, enhanced the activation of CD8+ and CD4+ T cells and increased the number of specific CD8+/IFN-γ+ T cells in lymphoid and nonlymphoid tissues in mice immunized by pB144. Immunization with pB144 and β-glu6 increased the anti-HBc IgG and IgG2a antibody titer. These results demonstrate that β-glu6 can enhance the virus-specific CTL and Th1 responses induced by DNA vaccine, suggesting β-glu6 as a candidate adjuvant in DNA vaccination

Prognostic role of GPER/Ezrin in triple-negative breast cancer is associated with menopausal status

The role of G protein-coupled estrogen receptor 1 (GPER) signaling, including promotion of Ezrin phosphorylation (which could be activated by estrogen), has not yet been clearly identified in triple-negative breast cancer (TNBC). This study aimed to evaluate the prognostic value of GPER and Ezrin in TNBC patients. Clinicopathologic features including age, menopausal status, tumor size, nuclear grade, lymph node metastasis, AJCC TNM stage, and ER, PR and HER-2 expression were evaluated from 249 TNBC cases. Immunohistochemical staining of GPER and Ezrin was performed on TNBC pathological sections. Kaplan–Meier analyses, as well as logistic regressive and Cox regression model tests were applied to evaluate the prognostic significance between different subgroups. Compared to the GPER-low group, the GPER-high group exhibited higher TNM staging (P = 0.021), more death (P < 0.001), relapse (P < 0.001) and distant events (P < 0.001). Kaplan–Meier analysis showed that GPER-high patients had a decreased OS (P < 0.001), PFS (P < 0.001), LRFS (P < 0.001) and DDFS (P < 0.001) than GPER-low patients. However, these differences in prognosis were not statistically significant in post-menopausal patients (OS, P = 0.8617; PFS, P = 0.1905; LRFS, P = 0.4378; DDFS, P = 0.2538). There was a significant positive correlation between GPER and Ezrin expression level (R = 0.508, P < 0.001) and the effect of Ezrin on survival prognosis corresponded with GPER. Moreover, a multivariable analysis confirmed that GPER and Ezrin level were both significantly associated with poor DDFS (HR: 0.346, 95% CI 0.182–0.658, P = 0.001; HR: 0.320, 95% CI 0.162–0.631, P = 0.001). Thus, overexpression of GPER and Ezrin may contribute to aggressive behavior and indicate unfavorable prognosis in TNBC; this may correspond to an individual’s estrogen levels

Comparative Analyses of H3K4 and H3K27 Trimethylations Between the Mouse Cerebrum and Testis

AbstractThe global features of H3K4 and H3K27 trimethylations (H3K4me3 and H3K27me3) have been well studied in recent years, but most of these studies were performed in mammalian cell lines. In this work, we generated the genome-wide maps of H3K4me3 and H3K27me3 of mouse cerebrum and testis using ChIP-seq and their high-coverage transcriptomes using ribominus RNA-seq with SOLiD technology. We examined the global patterns of H3K4me3 and H3K27me3 in both tissues and found that modifications are closely-associated with tissue-specific expression, function and development. Moreover, we revealed that H3K4me3 and H3K27me3 rarely occur in silent genes, which contradicts the findings in previous studies. Finally, we observed that bivalent domains, with both H3K4me3 and H3K27me3, existed ubiquitously in both tissues and demonstrated an invariable preference for the regulation of developmentally-related genes. However, the bivalent domains tend towards a “winner-takes-all” approach to regulate the expression of associated genes. We also verified the above results in mouse ES cells. As expected, the results in ES cells are consistent with those in cerebrum and testis. In conclusion, we present two very important findings. One is that H3K4me3 and H3K27me3 rarely occur in silent genes. The other is that bivalent domains may adopt a “winner-takes-all” principle to regulate gene expression

Function of Chick Subcutaneous Adipose Tissue During the Embryonic and Posthatch Period

Since excess abdominal fat is one of the main problems in the broiler industry for the development of modern broiler and layer industry, the importance of subcutaneous adipose tissue has been neglected. However, chick subcutaneous adipose tissue appeared earlier than abdominal adipose tissue and more than abdominal adipose tissue. Despite a wealth of data, detailed information is lacking about the development and function of chick subcutaneous adipose tissue during the embryonic and posthatch period. Therefore, the objective of the current study was to determine the developmental changes of adipocyte differentiation, lipid synthesis, lipolysis, fatty acid β-oxidation, and lipid contents from E12 to D9.5. The results showed that subcutaneous adipose tissue was another important energy supply tissue during the posthatch period. In this stage, the mitochondrial copy number and fatty acid β-oxidation level significantly increased. It revealed that chick subcutaneous adipose tissue not only has the function of energy supply by lipidolysis but also performs the same function as brown adipose tissue to some extent, despite that the brown adipose tissue does not exist in birds. In addition, this finding improved the theory of energy supply in the embryonic and posthatch period and might provide theoretical basis on physiological characteristics of lipid metabolism in chicks

Towards a high-intensity muon source at CiADS

The proposal of a high-intensity muon source driven by the CiADS linac, which has the potential to be one of the state-of-the-art facilities, is presented in this paper. We briefly introduce the development progress of the superconducting linac of CiADS. Then the consideration of challenges related to the high-power muon production target is given and the liquid lithium jet muon production target concept is proposed, for the first time. The exploration of the optimal target geometry for surface muon production efficiency and the investigation into the performance of liquid lithium jet target in muon rate are given. Based on the comparison between the liquid lithium jet target and the rotation graphite target, from perspectives of surface muon production efficiency, heat processing ability and target geometry compactness, the advantages of the new target concept are demonstrated and described comprehensively. The technical challenges and the feasibility of the free-surface liquid lithium target are discussed

Enhanced drug loading capacity of polypyrrole nanowire network for confrolled drug release

For a conducting polymer (CP) based drug release system, drug loading is often accomplished by a doping process, in which drug is incorporated into polymer as dopant. Therefore, the drug loading capacity is relatively low and the range of drugs can be loaded is limited. In the present work, a polypyrrole (PPy) nanowire network is prepared by an electrochemical method and it is found that the micro- and nano- gaps among the individual nanowires of the PPy nanowire network can be used as reservoir to store drugs. Therefore, the drug loading capacity is dependent on the volume of these micro- and nano-vacancies, instead of the doping level. The range of loaded drugs also can be theoretically extended to any drugs, instead of only charged dopants. In fact, it is confirmed here that both hydrophilic and lipophilic drugs can be loaded into the micro- and nano-gaps due to the amphilicity of the PPy nanowire network. As a result, both drug loading capacity and the range of drugs can be loaded are significantly improved. After being covered with a protective PPy film, controlled drug release from the prepared system is achieved by electrical stimulation (cyclic voltammetry, CV) and the amount of drug released can be controlled by changing the scan rate of CV and the thickness of the protective PPy film.Web of Scienc