Engineering topics
Publications and source records attributed to Luo, Yan.
The objective of this project is to develop and demonstrate the capabilities of a new acoustics-based blade structural health monitoring (SHM) system for offshore wind turbines.
We present a novel natural language processing (NLP) approach to deriving plain English descriptors for science cases otherwise restricted by obfuscating technical terminology. We address the limitations of common radio galaxy morphology classifications by applying this approach. We experimentally derive a set of semantic tags for the Radio Galaxy Zoo EMU (Evolutionary Map of the Universe) project and the wider astronomical community. We collect 8486 plain English annotations of radio galaxy morphology, from which we derive a taxonomy of tags. The tags are plain English. The result is an extensible framework, which is more flexible, more easily communicated, and more sensitive to rare feature combinations, which are indescribable using the current framework of radio astronomy classifications.
This paper presents an innovative approach to producing energy-dense, carbon–neutral liquid ammonia as a means for carrying energy. This approach synergistically integrates microwave reaction chemistry with novel heterogeneous catalysis that decouples dinitrogen activation from high-temperature and high-pressure reactions, altering reaction pathways and increasing ammonia formation rate. Results presented here demonstrate that ammonia synthesis can be conducted at 280 ? and ambient pressure to achieve ~1 mmol ammonia/g cat/h over supported ruthenium catalyst systems utilizing microwave irradiation. It is further shown that adding promoter ions such as potassium, cerium, and barium significantly improves the ammonia production rate over undoped ruthenium-based catalysts. This effect could be attributed to enhanced dielectric loss processes that lead to stronger microwave absorption by the catalyst. Measurement of the equilibrium constant under microwave conditions showed a higher ammonia yield than under thermal equilibrium conditions for both the iron- and ruthenium-based catalysts. Finally, this study also illustrates the advantages of using a variable-frequency microwave reactor for ambient-pressure ammonia synthesis. Mechanistically, investigators believed that the oscillating electric fields of the radiation can couple with adsorbed nitrogen on the surface and accelerate its dissociation. Since dinitrogen dissociation on the surface is rate limiting, this effectively accelerates the reaction.
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Reactions between molten iron, molten silicon steel, and ceramic materials are of great importance from the perspective of the corrosion of refractory material in the steelmaking and continuous casting processes. Reactions between liquid steel and aluminum nitride (AlN) substrate containing Al-Y-oxides were investigated using the sessile drop method at 1833 K (1560 °C). The liquid–substrate interface was observed with the increasing holding time, and the reaction mechanism was studied. In the case of the liquid iron and the silicon steel on the AlN substrate containing Al-Y-oxides, the reaction products on the steel side of the interface between the steel and the substrate were Al-rich Al-Y-oxides and Al{sub 2}O{sub 3} particles. For silicon steel and pure AlN substrate, Al{sub 2}O{sub 3} particles were the main products. Contact angles were lower for liquid iron than for silicon steel due to the higher oxygen content in iron. In addition, the solid–liquid interfacial tension and the work of adhesion between AlN and steel were measured.
In the previous research, our group designed and synthesized 2,3,4,5-tetrahydro-1H-pyrido-[4,3-b] indoles, which showed high anti-tumor activity. In this study, a series of novel 2,3,4,5-tetrahydro-1H-pyrido-[4,3-b] indole derivatives were designed by introducing an alkyl or aralkyl and a sulfonyl group, which are considered as the pharmacophores of some antitumor drugs based on the combination principles, and synthesized. The antiproliferative activity of all the target compounds were evaluated against Hela, A549, HepG2, and MCF-7 cell lines using the MTT assay in vitro. The results were represented by IC{sub 50} values. All compounds showed moderate to excellent antiproliferative activity with IC{sub 50} values between 0 μM and 100 μM against cancer cells. The proliferations of Hela, A549, HepG2, and MCF-7 cell lines were inhibited in a dose-dependent manner, and the cytolytic activity was markedly inhibited at the same time. The IC{sub 50} values of intermediate 3 inhibited against Hela, A549, HepG2, and MCF-7 cell lines were 52.75, 50.30, 60.31, and 54.39 μM, respectively, which were higher than the new compounds that we expected. The compounds 4a–4d bearing sulfonyl, substituted by electron donating group, showed moderate to significant antiproliferative activity, in which compound 4c was the best with the IC{sub 50} values of 13.71, 9.42, 15.06, and 14.77 μM, and these results suggested that the introduction of sulfonyl could increase the antiproliferative activity of 2,3,4,5-tetrahydro-1H-pyrido-[4,3-b]indole. Compounds 4e–4g bearing alkyl, phenyl, and arylated alkyl produced good antiproliferative activity and the IC{sub 50} value of 4g was lower than 30 μM. The target compounds were more potent against A549 compared to the other three cell lines. Molecular docking studies revealed the binding orientations of all the synthesized compounds in the active site of c-Met. Moreover, molecular dynamics simulations have been performed to evaluate the binding stabilities between the synthesized compounds and their receptors.
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A complex nitride of Al{sub x}Mg{sub (1−x)}N was observed in silicon steels. A thermodynamic model was developed to predict the ferrite/nitride equilibrium in the Fe-Al-Mg-N alloy system, using published binary solubility products for stoichiometric phases. The model was used to estimate the solubility product of nitride compound, equilibrium ferrite, and nitride compositions, and the amounts of each phase, as a function of steel composition and temperature. In the current model, the molar ratio Al/(Al + Mg) in the complex nitride was great due to the low dissolved magnesium in steel. For a steel containing 0.52 wt pct Al{sub s}, 10 ppm T.Mg., and 20 ppm T.N. at 1100 K (827 °C), the complex nitride was expressed by Al{sub 0.99496}Mg{sub 0.00504}N and the solubility product of this complex nitride was 2.95 × 10{sup −7}. In addition, the solution temperature of the complex nitride increased with increasing the nitrogen and aluminum in steel. The good agreement between the prediction and the detected precipitate compositions validated the current model.
The evolution of inclusions in oriented silicon steel during the manufacturing process was carried out by chemical composition analysis, non-aqueous electrolytic corrosion, and thermodynamic calculation. The morphology, composition, and size of inclusions were analyzed introducing field emission scanning electron microscope. The oxides were mainly formed during the secondary refining, and the nitrides, sulfides, and compounds were formed during the solidification and cooling of steel in the processes of continuous casting and hot rolling.
Gastric cancer is one of the most lethal malignancies worldwide. Chronic Helicobacter pylori (H. pylori) infection can induce an inflammatory response that promotes atrophic gastritis, a preceding event to cancer development. The type 1 regulatory T (Tr1) cells have recently emerged as a critical participant in maintaining self-tolerance. In this study, we examined Tr1 cells in H. pylori infection and gastric cancer development. While H. pylori-uninfected (uninfected) subjects presented low Tr1 frequency in the peripheral blood, H. pylori-infected asymptomatic (infected) individuals and H. pylori-infected gastric cancer (cancer) individuals both presented elevated Tr1 frequency. Although the Tr1 cells from infected asymptomatic subjects were functionally more potent than those from uninfected healthy subjects, the Tr1 cells in cancer individuals demonstrated several functional impairments, such as reduced interleukin 10 (IL-10) expression, lower secretion of cytolytic factors including granzyme B and perforin, and lower capacity to suppress CD4{sup +}CD25{sup -} T cell and CD8{sup +} T cell proliferation. In addition, the frequency and function of Tr1 cells were positively correlated with the disease-free survival of the gastric cancer patients. These results suggest that Tr1 cells might be involved in the regulating immune responses in H. pylori infection and gastric cancer development. The fact that Tr1 cells could suppress inflammation and produce cytotoxic molecules at the same time has made them attractive potential candidates for future immunotherapies.
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In 2014, the identification of stone fruits contaminated with led to the subsequent identification of a multistate outbreak. Simultaneous detection and enumeration of L. monocytogenes were performed on 105 fruits, each weighing 127 to 145 g, collected from 7 contaminated lots. The results showed that 53.3% of the fruits yielded L. monocytogenes (lower limit of detection, 5 CFU/fruit), and the levels ranged from 5 to 2,850 CFU/fruit, with a geometric mean of 11.3 CFU/fruit (0.1 CFU/g of fruit). Two serotypes, IVb-v1 and 1/2b, were identified by a combination of PCR- and antiserum-based serotyping among isolates from fruits and their packing environment; certain fruits contained a mixture of both serotypes. Single nucleotide polymorphism (SNP)-based whole-genome sequencing (WGS) analysis clustered isolates from two case-patients with the serotype IVb-v1 isolates and distinguished outbreak-associated isolates from pulsed-field gel electrophoresis (PFGE)-matched, but epidemiologically unrelated, clinical isolates. The outbreak-associated isolates differed by up to 42 SNPs. All but one serotype 1/2b isolate formed another WGS cluster and differed by up to 17 SNPs. Fully closed genomes of isolates from the stone fruits were used as references to maximize the resolution and to increase our confidence in prophage analysis. Putative prophages were conserved among isolates of each WGS cluster. All serotype IVb-v1 isolates belonged to singleton sequence type 382 (ST382); all but one serotype 1/2b isolate belonged to clonal complex 5.
Virginia is the third largest producer of fresh-market tomatoes in the United States. Tomatoes grown along the eastern shore of Virginia are implicated almost yearly in Salmonella illnesses. Traceback implicates contamination occurring in the pre-harvest environment. To get a better understanding of the ecological niches of Salmonella in the tomato agricultural environment, a 2-year study was undertaken at a regional agricultural research farm in Virginia. Environmental samples, including tomato (fruit, blossoms, and leaves), irrigation water, surface water and sediment, were collected over the growing season. These samples were analyzed for the presence of Salmonella using modified FDA-BAM methods. Molecular assays were used to screen the samples. Over 1500 samples were tested. Seventy-five samples tested positive for Salmonella yielding over 230 isolates. The most commonly isolated serovars were S. Newport and S. Javiana with pulsed-field gel electrophoresis yielding 39 different patterns. Genetic diversity was further underscored among many other serotypes, which showed multiple PFGE subtypes. Whole genome sequencing (WGS) of several S. Newport isolates collected in 2010 compared to clinical isolates associated with tomato consumption showed very few single nucleotide differences between environmental isolates and clinical isolates suggesting a source link to Salmonella contaminated tomatoes. Nearly all isolates collected during two growing seasons of surveillance were obtained from surface water and sediment sources pointing to these sites as long-term reservoirs for persistent and endemic contamination of this environment.
An rf linear accelerator for producing an electron beam. The outer wall of the rf cavity of said linear accelerator being perforated to allow gas inside said rf cavity to flow to a pressure chamber surrounding said rf cavity and having means of ultra high vacuum pumping of the cathode of said rf linear accelerator. Said rf linear accelerator is used to accelerate polarized or unpolarized electrons produced by a photocathode, or to accelerate thermally heated electrons produced by a thermionic cathode, or to accelerate rf heated field emission electrons produced by a field emission cathode.
Using an observing system simulation experiment (OSSE), we investigate the potential soil moisture retrieval capability of the National Aeronautics and Space Administration (NASA) Aquarius radiometer (L-band 1.413 GHz) and scatterometer (L-band, 1.260 GHz). We estimate potential errors in soil moisture retrievals and identify the sources that could cause those errors. The OSSE system includes (i) a land surface model in the NASA Land Information System, (ii) a radiative transfer and backscatter model, (iii) a realistic orbital sampling model, and (iv) an inverse soil moisture retrieval model. We execute the OSSE over a 1000 2200 km2 region in the central United States, including the Red and Arkansas river basins. Spatial distributions of soil moisture retrieved from the radiometer and scatterometer are close to the synthetic truth. High root mean square errors (RMSEs) of radiometer retrievals are found over the heavily vegetated regions, while large RMSEs of scatterometer retrievals are scattered over the entire domain. The temporal variations of soil moisture are realistically captured over a sparely vegetated region with correlations 0.98 and 0.63, and RMSEs 1.28% and 8.23% vol/vol for radiometer and scatterometer, respectively. Over the densely vegetated region, soil moisture exhibits larger temporal variation than the truth, leading to correlation 0.70 and 0.67, respectively, and RMSEs 9.49% and 6.09% vol/vol respectively. The domain-averaged correlations and RMSEs suggest that radiometer is more accurate than scatterometer in retrieving soil moisture. The analysis also demonstrates that the accuracy of the retrieved soil moisture is affected by vegetation coverage and spatial aggregation.