Engineering topics
Lu, Na
Publications and source records attributed to Lu, Na.
FaceBase 3: analytical tools and FAIR resources for craniofacial and dental research
ABSTRACT The FaceBase Consortium was established by the National Institute of Dental and Craniofacial Research in 2009 as a ‘big data’ resource for the craniofacial research community. Over the past decade, researchers have deposited hundreds of annotated and curated datasets on both normal and disordered craniofacial development in FaceBase, all freely available to the research community on the FaceBase Hub website. The Hub has developed numerous visualization and analysis tools designed to promote integration of multidisciplinary data while remaining dedicated to the FAIR principles of data management (findability, accessibility, interoperability and reusability) and providing a faceted search infrastructure for locating desired data efficiently. Summaries of the datasets generated by the FaceBase projects from 2014 to 2019 are provided here. FaceBase 3 now welcomes contributions of data on craniofacial and dental development in humans, model organisms and cell lines. Collectively, the FaceBase Consortium, along with other NIH-supported data resources, provide a continuously growing, dynamic and current resource for the scientific community while improving data reproducibility and fulfilling data sharing requirements.
Investigation of Electrical and Magnetic Properties of La{sup 3+} Substituted M-Type Ba–Ni Nano-Ferrites
In this paper, La{sup 3+} substituted M-type Ba–Ni hexaferrite nanoparticles having composition Ba{sub 0.8}Ni{sub 0.2}Fe{sub 12-x}La{sub x}O{sub 19} (x = 0, 0.2, 0.4, 0.6, and 0.8) were prepared by co-precipitation route. The phase of the grown NPs was confirmed using X-ray diffraction analysis and results reveal the growth of M-type hexaferrite NPs as a major phase. The energy dispersive X-ray spectroscopy (EDX) was employed to determine the elemental composition of prepared samples. The FTIR spectra of synthesized samples confirm the bond formation of M-type hexaferrites. The optical bandgap was determined by UV-Vis spectroscopy and the results exhibit an increase in optical bandgap with decreasing crystallite size. The vibrating sample magnetometry (VSM) technique was used to analyze the effect of dopant on the magnetic properties like coercivity, saturation magnetization, and remanence of the synthesized samples. The electrical resistivity was measured by two probe method and it was observed that the activation energy shows a decreasing trend with increase in La content. The highly resistive nature of prepared nano ferrites indicates the potential to use these ferrites for high-frequency applications.
Strain-stress study of Al x Ga 1–x N/AlN heterostructures on c-plane sapphire and related optical properties
This work presents a systematic study of stress and strain of Al x Ga 1-x N/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using synchrotron radiation high-resolution X-ray diffraction and reciprocal space mapping. The c-plane of the Al x Ga 1-x N epitaxial layers exhibits compressive strain, while the alpha-plane exhibits tensile strain. The biaxial stress and strain are found to increase with increasing Al composition, although the lattice mismatch between the Al x Ga 1-x N and the buffer layer AlN gets smaller. A reduction in the lateral coherence lengths and an increase in the edge and screw dislocations are seen as the Al x Ga 1-x N composition is varied from GaN to AlN, exhibiting a clear dependence of the crystal properties of Al x Ga 1-x N on the Al content. The bandgap of the epitaxial layers is slightly lower than predicted value due to a larger tensile strain effect on the alpha-axis compared to the compressive strain on the c-axis. Raman characteristics of the Al x Ga 1-x N samples exhibit a shift in the phonon peaks with the Al composition. The effect of strain on the optical phonon energies of the epitaxial layers is also discussed
A review of long fibre thermoplastic (LFT) composites [A review of long fibre-reinforced thermoplastic of long fibre thermoplastic (LFT) composites]
Long fibre-reinforced thermoplastic or long fibre thermoplastic (LFT) composites possess superior specific modulus and strength, excellent impact resistance, and other advantages such as ease of processability, recyclability, and excellent corrosion resistance. These advantages make LFT composites one of the most advanced lightweight engineering materials and enable their increasing use in various applications. This review paper summarizes the research and development work that has been conducted on LFT composites since their initial development. Different aspects of LFTs, such as process development, fibre orientation distribution (FOD), fibre length distribution (FLD), and their effects on the mechanical properties of LFT composites are described. The characterization of the FOD and FLD in the LFT composites using advanced imaging technology such as high-resolution 3D micro-CT scanning technique is summarized. Research and development of LFT hybridisation and LFT additives are also discussed. Lastly, conclusions are made and the future outlook of LFT composites is given.
The use of strain to tailor electronic thermoelectric transport properties: A first principles study of 2H-phase CuAlO 2
Using first principles calculations, the use of strain to adjust electronic transport and the resultant thermoelectric (TE) properties is discussed using 2H phase CuAlO 2 as a test case. Transparent oxide materials, such as CuAlO 2 , a p-type transparent conducting oxide (TCO), have recently been studied for high temperature thermoelectric power generators and coolers for waste heat. Given TCO materials with relative ease of fabrication, low cost of materials, and non-toxicity, the ability to tailor them to specific temperature ranges, power needs, and size requirements, through the use of strain opens an interesting avenue. We find that strain can have a significant effect on these properties, in some cases detrimental and in others beneficial, including the potential for n-type power factors larger than the highest p-type case. The physical reasons for this behavior are explained in the terms of the thermoelectric transport distribution and the Landauer distribution of modes.
Temperature dependent thermoelectric properties of cuprous delafossite oxides
The use of nanostructured delafossite oxides in thermoelectric (TE) applications has attracted a great interest due to their high performance and long-term stability at elevated temperatures. Cuprous delafossites, CuMO 2 (M=Al, Cr, Fe, Ga, Mn), compared to conventional TE materials, such as Bi 2 Te 3 , PbTe and SiGe, are non-toxic and more earth abundant. In particular, CuAlO 2 compound shows a great potential for high performance thermoelectric materials. In this work, a systematic study of temperature dependent TE properties of cuprous delafossite materials, CuAlO 2 , is reported. The optimization of the TE properties has been realized by controlling nanostructure size around 80 nm CuAlO 2 powder was prepared using a solid-state synthesis method at ~1373 K in nitrogen/air atmosphere. The nanostructure size was controlled by a high energy ball milling process. Reducing the particle size of nanostructured bulk materials decouples interdependent electron and phonon transport and results in a lattice thermal conductivity decrease without deteriorating electrical conductivity. As a result, the high effective mass plays a dominant role in the high Seebeck coefficient and low electrical conductivity. The power factor reached ~0.78×10 -5 W/mK 2 at 780 K. Temperature dependent TE properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity are analyzed. The processing-structure-property correlation of these materials are discussed.
LZ205, a newly synthesized flavonoid compound, exerts anti-inflammatory effect by inhibiting M1 macrophage polarization through regulating PI3K/AKT/mTOR signaling pathway
Highlights: • LZ205 reduced M1[HYPHEN]associated cytokines secretion without affecting M2 macrophages. • LZ205 significantly blocked expression of PI3K, p-Akt and p-mTOR in macrophages. • LZ205 significantly inhibited M1 macrophages polarization in DSS-induced colitis and alum-induced murine peritonitis. Macrophage polarization is involved in the process of inflammation. Regulation of macrophage polarization is considered to be an effective method for the treatment of various inflammatory diseases. In our study, we investigated the potential molecular mechanism of the flavonoid compound LZ205, which exhibits anti-inflammatory property. Results showed that LZ205 significantly reduced M1 macrophage-associated proinflammatory cytokines secretion by regulating PI3K/AKT/mTOR signaling pathway without affecting M2 macrophage-associated cytokines mRNA levels. In vivo studies showed that LZ205 significantly inhibited M1 macrophages polarization in DSS-induced colitis and alum-induced murine peritonitis. Consistent with in vitro studies, LZ205 significantly blocked expression of PI3K, p-AKT and p-mTOR in colon tissues and peritoneal macrophages. Taken together, LZ205 exerts anti-inflammatory effect by inhibiting M1 macrophage polarization via regulating PI3K/AKT/mTOR signaling pathway.
The structural properties of InGaN alloys and the interdependence on the thermoelectric behavior
The III-Nitrides are promising candidate for high efficiency thermoelectric (TE) materials and devices due to their unique features which includes high thermal stability. A systematic study of the room temperature TE properties of metalorganic chemical vapor deposition grown In{sub x}Ga{sub 1-x}N were investigated for x = 0.07 to 0.24. This paper investigated the role of indium composition on the TE properties of InGaN alloys in particular the structural properties for homogenous material that did not show significant phase separation. The highest Seebeck and power factor values of 507 μV K{sup −1} and 21.84 × 10{sup −4} Wm{sup −1}K{sup −1} were observed, respectively for In{sub 0.07}Ga{sub 0.93}N at room temperature. The highest value of figure-of-merit (ZT) was calculated to be 0.072 for In{sub 0.20}Ga{sub 0.80}N alloy at room temperature.
Wogonin inhibits tumor angiogenesis via degradation of HIF-1α protein
Wogonin, a plant-derived flavone, has been shown recently to have antitumor effects. However, the mechanisms that wogonin inhibits tumor angiogenesis are not well known. In this study, we investigated the effects of wogonin on expression of hypoxia-inducible factor-1α (HIF-1α) and secretion of vascular endothelial growth factor (VEGF) in tumor cells. We found that wogonin decreased the expression of HIF-1α by affecting its stability and reduced the secretion of VEGF, which suppressed angiogenesis in cancer. Wogonin promoted the degradation of HIF-1α by increasing its prolyl hydroxylation, which depended on prolyl hydroxylase (PHD) and the von Hippel–Lindau tumor suppressor (VHL). Intriguingly, wogonin impeded the binding between heat-shock protein 90 (Hsp90) and HIF-1α. In addition, wogonin down-regulated the Hsp90 client proteins EGFR, Cdk4 and survivin, but did not affect the level of Hsp90. Wogonin also increased ubiquitination of HIF-1α and promoted its degradation in proteasome. We also found that wogonin could inhibit nuclear translocation of HIF-1α. Electrophoresis mobility shift assay (EMSA) showed that wogonin decreased the binding activity of exogenous consensus DNA oligonucleotide with HIF-1α in nuclear extracts from MCF-7 cells. Chromatin immunoprecipitation (ChIP) assay also revealed that HIF-1α directly binded to endogenous hypoxia-responsive element (HRE) and this binding was significantly decreased in MCF-7 cells treated with wogonin. Preliminary results indicated in vivo activity of wogonin against xenograft-induced angiogenesis in nude mice. Taken together, the results suggested that wogonin was a potent inhibitor of HIF-1α and provided a new insight into the mechanisms of wogonin against cancers. - Highlights: • Wogonin is an all around inhibitor of VEGF signaling. • We firstly demonstrate that wogonin inhibits secretion of VEGF by decreasing HIF-1α. • Wogonin enhances PDH and VHL expression and inhibits Hsp90 function. • Wogonin decreases HIF-1α nuclear import and binding to DNA. • Wogonin may be a potent HIF-1α inhibitor for cancer therapeutics in the future.
Sonic hedgehog initiates cochlear hair cell regeneration through downregulation of retinoblastoma protein
Highlights: Black-Right-Pointing-Pointer Shh activation in neonatal cochleae enhances sensory cell proliferation. Black-Right-Pointing-Pointer Proliferating supporting cells can transdifferentiate into hair cells. Black-Right-Pointing-Pointer Shh promotes proliferation by transiently modulating pRb activity. Black-Right-Pointing-Pointer Shh inhibits pRb by inhibiting transcription and increasing phosphorylation of pRb. -- Abstract: Cell cycle re-entry by cochlear supporting cells and/or hair cells is considered one of the best approaches for restoring hearing loss as a result of hair cell damage. To identify mechanisms that can be modulated to initiate cell cycle re-entry and hair cell regeneration, we studied the effect of activating the sonic hedgehog (Shh) pathway. We show that Shh signaling in postnatal rat cochleae damaged by neomycin leads to renewed proliferation of supporting cells and hair cells. Further, proliferating supporting cells are likely to transdifferentiate into hair cells. Shh treatment leads to inhibition of retinoblastoma protein (pRb) by increasing phosphorylated pRb and reducing retinoblastoma gene transcription. This results in upregulation of cyclins B1, D2, and D3, and CDK1. These results suggest that Shh signaling induces cell cycle re-entry in cochlear sensory epithelium and the production of new hair cells, in part by attenuating pRb function. This study provides an additional route to modulate pRb function with important implications in mammalian hair cell regeneration.
Net-Zero Energy Building Operator Training Program (NZEBOT)
The primary objective of the Net-Zero Energy Building Operator Training Program (NZEBOT) was to develop certificate level training programs for commercial building owners, managers and operators, principally in the areas of energy / sustainability management. The expected outcome of the project was a multi-faceted mechanism for developing the skill-based competency of building operators, owners, architects/engineers, construction professionals, tenants, brokers and other interested groups in energy efficient building technologies and best practices. The training program draws heavily on DOE supported and developed materials available in the existing literature, as well as existing, modified, and newly developed curricula from the Department of Engineering Technology & Construction Management (ETCM) at the University of North Carolina at Charlotte (UNC-Charlotte).