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Liu, Yan

Publications and source records attributed to Liu, Yan.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Fe-doping induced suppression of the second magnetic transition in Sr 4 Ru 3 O 10

Ruthenium oxide (Sr 4 Ru 3 O 10 ) exhibits a second magnetic transition at a temperature T M below its ferromagnetic (FM) transition (T C ~ 105 K), which has attracted considerable attention in the past two decades. Here, we successfully grew Sr 4 (Ru 1–x Fe x ) 3 O 10 (x = 0.01) crystal and systematically investigated the magnetotransport property of its nanosheets. We found a feature that there is an in-plane FM order aligned along < 110 > directions below T C without the occurrence of the second magnetic transition at T M , which is in contrast to that expected in pure Sr 4 Ru 3 O 10 nanosheets, where the in-plane FM order will rotate to the c direction below T M . Furthermore, a metamagnetic-like transition is also observed below ~50 K at about 2 T when the magnetic field is applied along the c axis. Finally, these results unambiguously demonstrate that the second magnetic transition at T M is actually a consequence of spin reorientation induced by the inherent coupling between the spin and lattice, which can be effectively tuned by element doping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Efficient Long-range, Directional Energy Transfer through DNA-Templated Dye Aggregates

The benzothiazole cyanine dye, K21, forms dye aggregates on double stranded DNA (dsDNA) templates. These aggregates exhibit a red-shifted absorption band, enhanced fluorescence emission and an increased fluorescence lifetime, all indicating strong excitonic coupling among the dye molecules. K21 aggregate formation on dsDNA is only weakly sequence dependent, providing a flexible approach that is adaptable to many different DNA nanostructures. Donor (D) – bridge (B) – Acceptor (A) complexes consisting of Alexa Fluor 350 as the donor, a 30 bp (9.7 nm) DNA templated K21 aggregate as the bridge and Alexa Fluor 555 as the acceptor show an overall donor to acceptor energy transfer efficiency of ~60%, with the loss of excitation energy being almost exclusively at the donor-bridge junction (63%). There was almost no excitation energy loss due to transfer through the aggregate bridge and the transfer efficiency from the aggregate to the acceptor was about 96%. By comparing the energy transfer in templated aggregates at several lengths up to 32 nm, the loss of energy per nanometer through the K21 aggregate bridge was determined to be <1%, suggesting that it should be possible to construct structures that use much longer energy transfer “wires” for light-harvesting applications in photonic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Deoxidation Mechanism in Reduced Titanium Powder Prepared by Multistage Deep Reduction of TiO{sub 2}

There are technical bottlenecks in the preparation of metallic titanium powder by conventional thermal reduction of TiO{sub 2} with calcium, magnesium, or other metals, such as low efficiency and incomplete deoxidation. Based on the thermodynamic equilibrium characteristics of the step-by-step reduction of TiO{sub 2}, a comparative study method was used, and the thermodynamic and kinetic differences between thermal reduction reactions of TiO{sub 2} with magnesia and calcium were investigated in this paper. Considering the difference in the electronegativity characteristics between magnesium and calcium, a new idea was put forward that the primary reduction product is prepared through a primary reduction process of TiO{sub 2} in the form of magnesiothermic self-propagating high-temperature synthesis (SHS), and then the reduced titanium powder is obtained through the primary reduction product for a deep calcium-thermal reduction reaction. The reduction degree and mechanism of TiO{sub 2} during the primary magnesium thermal reaction and deoxidation mechanism of primary reduction products in different deep reduction modes were investigated in this paper. The results showed that it is more conducive to undergo complete deoxygenation such that the primary reduction product is first acid impregnated, followed by deep calciothermic reduction. High-purity reduced titanium powder with a final oxygen content of only 0.21 pct and purity greater than 99.0 pct was obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Programming molecular topologies from single-stranded nucleic acids

Molecular knots represent one of the most extraordinary topological structures in biological polymers. Creating highly knotted nanostructures with well-defined and sophisticated geometries and topologies remains challenging. Here, we demonstrate a general strategy to design and construct highly knotted nucleic acid nanostructures, each weaved from a single-stranded DNA or RNA chain by hierarchical folding in a prescribed order. Sets of DNA and RNA knots of two- or three-dimensional shapes have been designed and constructed (ranging from 1700 to 7500 nucleotides), and they exhibit complex topological features, with high crossing numbers (from 9 up to 57). These single-stranded DNA/RNA knots can be replicated and amplified enzymatically in vitro and in vivo. Furthermore, this work establishes a general platform for constructing nucleic acid nanostructures with complex molecular topologies.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Investigation of the Carbochlorination Mechanism of Mullite from Fly Ash

In this study, the reaction mechanism of mullite carbochlorination was investigated to determine its potential in the use of high-alumina fly ash. Thermodynamic analysis of carbochlorination reduction was conducted to determine the two-stage mechanism of carbochlorination of the system Al{sub 6}Si{sub 2}O{sub 13}-C-Cl{sub 2}. The calculation results agreed well with the experimental results. The maximum chlorination rates of Al{sub 2}O{sub 3}, SiO{sub 2}, CaO, and TiO{sub 2} were 84.80, 55.96, 75.78, and 76.61 pct, respectively, under the optimum conditions: carbon:alumina molar ratio 3:1, temperature 1000 °C, pellet diameter 8 mm, and an average Cl{sub 2} flow 0.3544 L/min. X-ray diffraction analysis showed that the tailings from carbochlorination for 30 minutes mainly consisted of Al{sub 4.59}Si{sub 1.41}O{sub 9.7}, Al{sub 2}O{sub 3}, and SiO{sub 2}. A new SiO{sub 2} phase appeared in the tailings during carbochlorination. The morphology of the tailings after pelletizing carbochlorination was investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that under the action of carbon and chlorine, the original stable structure of mullite in the fly ash was destroyed. These findings provide useful information for facilitating the development of a pelletizing carbochlorination method for efficient and clean use of fly ash.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Wound-induced polypeptides improve resistance against Pseudomonas syringae pv. tomato DC3000 in Arabidopsis

Wound-induced polypeptides (WIPs) are a novel class of polypeptides with the length less than 100 amino acids. Our previous research has identified a number of WIP genes in soybean (Glycine max) root nodules. However, functions of WIPs in planta remains largely unknown. Here, we identified five WIP-encoding genes, AtWIP1-5, in Arabidopsis. Among them, AtWIP1 and -2 are ubiquitously expressed in a partially overlapping pattern as revealed by both qRT-PCR and promoter:GUS assays. Subcellular localization analyses reveal that both AtWIP1 and -2 are localized at the plasma membrane while AtWIP1 shows a punctate distribution pattern. AtWIP1, -2 are transcriptionally induced by flg22 treatment, but repressed by effector(s) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). Heterologous overexpression of GmWIP genes enhances resistance of Arabidopsis to Pst DC3000 at the cost of growth inhibition. Moreover, overexpression of GmWIP genes promotes pattern-triggered immunity (PTI) evidenced by increased expressions of flg22-inducible genes and enhanced seedling growth inhibition under flg22 treatment. Taken together, our results indicate that WIPs positively regulate plant resistance against Pst DC3000 by enhancing PTI responses.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Self‐Assembly of a 3D DNA Crystal Structure with Rationally Designed Six‐Fold Symmetry

Abstract Programming self‐assembled designer DNA crystals with various lattices and functions is one of the most important goals for nanofabrication using nucleic acids. The resulting porous materials possess atomic precision for several potential applications that rely on crystalline lattices and cavities. Herein, we present a rationally designed and self‐assembled 3D DNA crystal lattice with hexagonal symmetry. In our design, two 21‐base oligonucleotides are used to form a duplex motif that further assembles into a 3D array. The interactions between the strands are programmed using Watson–Crick base‐pairing. The six‐fold symmetry, as well as the chirality, is directed by the Holliday junctions formed between the duplex motifs. The rationally designed DNA crystal provides a new avenue that could create self‐assembled macromolecular 3D crystalline lattices with atomic precision. In addition, the structure contains a highly organized array of well‐defined cavities that are suitable for future applications with immobilized guests.

Zhang, Fei↗
DOE OSTI2018

ST6GAL1 negatively regulates monocyte transendothelial migration and atherosclerosis development

Highlights: • ST6GAL1 expression is inversely related to atherosclerosis development. • Knockdown of ST6GAL1 in vascular endothelial cells directly promotes monocyte transendothelial migration. • ST6GAL1 overexpression inhibits TNFα-induced monocyte transendothelial migration. • β-catenin sialylation level is downregulated in inflammatory endothelial cells. Monocyte transendothelial migration is a critical step in the initial stage of atherosclerosis, in which the involvement of α-2,6 sialyltransferase 1 (ST6GAL1) has been confirmed by increasing evidence. But the direct relationship between ST6GAL1 and atherosclerosis remains incompletely uncertain. In this study, we demonstrated that the expression level of ST6GAL1 in vascular endothelium was significantly decreased in atherosclerosis development process, while obviously recovered after atherosclerosis regression. Further analysis showed that knockdown of ST6GAL1 by RNA interference in vascular endothelial cells EA. hy926 obviously promoted TNFα-triggered monocyte-transendothelial migration, whereas overexpression of ST6GAL1 strongly inhibited monocyte-transendothelial migration. Moreover, we firstly found β-catenin is a sialylated protein and its sialylation level is decreased in TNFα-treated EA. hy926 cells, suggesting that the function of ST6GAL1 in preventing both atherosclerosis development and monocyte transendothelial migration might result from the sialylation of β-catenin of endothelium. Our results suggested ST6GAL1 might be a potential target for atherosclerosis prevention and treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Alpha7 nicotinic acetylcholine receptor activation protects against myocardial reperfusion injury through modulation of autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) activation alleviates myocardial ischemia/reperfusion (MI/R) injury. However, the underlying mechanisms remain unclear. Here, we investigated the role of autophagy in α7nAChR-mediated cardioprotection and the molecular mechanisms involved. Activating α7nAChR with PNU-282987 at the initiation of reperfusion reduced myocardial infarct size in MI/R rats. PNU-282987 treatment also significantly inhibited MI/R-induced myocardial autophagy dysfunction as evidenced by the reduction of LC3-II/LC3-I ratio, Beclin-1 and p62 abundance. In addition, PNU-282987 treatment reduced hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury in vitro, accompanied with the inhibition of Beclin-1-associated autophagy and the restoration of autophagic flux. Interestingly, inhibiting autophagic flux attenuated α7nAChR-afforded improvement of mitochondrial function as well as inhibition of apoptosis in vitro. Mechanistically, co-administration of PNU-282987 with LY294002 (a PI3K inhibitor), AG490 (a JAK2 inhibitor) or Bcl-2 siRNA, but not compound C (an AMPK inhibitor), reduced Bcl-2 level and prevented the modulation of autophagy afforded by PNU-282987 in H/R cardiomyocytes. Collectively, these findings suggest that α7nAChR activation inhibits Beclin-1-associated autophagy dysfunction via the JAK2/Bcl-2 and PI3K/Bcl-2 cascades, leading to cardioprotection against MI/R injury.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Salinization of porewater in a multiple aquitard-aquifer system in Jiangsu coastal plain, China

Chemical and isotopic compositions were analyzed in porewater squeezed from a clayey aquitard in Jiangsu coastal plain, eastern China, to interpret the salinity origin, chemical evolution and water-mass mixing process. A strong geochemical fingerprint was obtained with an aligned Cl/Br ratio of 154 in the salinized aquitard porewater over a wide Cl{sup −} concentration range (396–9,720 mg/L), indicating that porewater salinity is likely derived from a mixing with old brine with a proportion of less than 20%. Very small contributions of brine exerted limited effects on water stable isotopes. The relationships between porewater δ{sup 18}O and δD indicate that shallow and intermediate porewaters could be original seawater and were subsequently diluted with modern meteoric water, whereas deep porewaters with depleted stable isotopic values were probably recharged during a cooler period and modified by evaporation and seawater infiltration. The cation–Cl relationship and mineralogy of associated strata indicate that porewater has been chemically modified by silicate weathering and ion-exchange reactions. {sup 87}Sr/{sup 86}Sr ratios of 0.7094–0.7112 further confirm the input source of silicate minerals. Numerical simulations were used to evaluate the long-term salinity evolution of the deep porewater. The alternations of boundary conditions (i.e., the third aquifer mixed with brine at approximately 70 ka BP, followed by recharge of glacial meltwater at 20–25 ka BP, and then mixing with Holocene seawater at 7–10 ka BP) are responsible for the shift in porewater salinity. These timeframes correspond with the results of previous studies on ancient marine transgression-regression in Jiangsu coastal plain.

58 GEOSCIENCES↗
DOE OSTI2017

Upregulation of PAG1/Cbp contributes to adipose-derived mesenchymal stem cells promoted tumor progression and chemoresistance in breast cancer

C-terminal Src kinase (Csk)-binding protein (Cbp) is a ubiquitously expressed transmembrane adaptor protein which regulating Src family kinase (SFK) activities. Although SFKs are well known for their involvement in breast cancer, the function of Cbp in breast carcinogenesis upon the adipose-tumor microenvironment has not been investigated. Here, we reported that adipose-derived mesenchymal stem cells (ASCs) induced increased expression of Cbp accompanied by enhanced cell proliferation and chemotherapy resistance in breast cancer cell MCF-7/ADR. Depletion of Cbp in breast cancer cell by RNA interference led to remarkable inhibition of cell proliferation, invasion as well as synergy with adriamycin hydrochloride to suppress the tumor growth. Furthermore, silencing of Cbp concomitantly inhibited the expression of phosphoryl of Src, AKT and mTOR signals. Our study highlights the underlying mechanism of cross interaction between ASCs and breast cancer cells, and indicates that PAG1/Cbp in breast cancer cell may modulate tumor progression and acquired chemoresistance in the ASCs-associated breast cancer microenvironment through Src and AKT/mTOR pathways.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Structure transformation of Ti films deposited on SiC single crystal substrates

Highlights: • In this paper, an interesting intermediate state of the fcc-hcp transformation in Ti films was observed. • We figured this intermediate structure out by XRD and HRTEM. • The formation of this intermediate state and the mechanism of thickness-dependent fcc-hcp transformation were discussed. - Abstract: This paper reports the structure transformation of Ti films deposited on SiC(0001) single crystal substrates using DC magnetron sputtering. Film thickness, sputter power and temperature of deposition were changed to investigate structure transformation of Ti films. The structure characterization of Ti film was performed by means of X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscope (HRTEM). The results showed that the Ti film grew epitaxially with a face centered cubic (fcc) structure even the thickness is up to about 50 nm. High temperature and low sputter power are propitious to the formation of fcc-Ti. An interesting intermediate state of the fcc-hcp transformation was observed. This intermediate structure could help us to understand the mechanism of thickness-dependent fcc-hcp transformation in Ti thin films.

36 MATERIALS SCIENCE↗
NASA NTRS2017

Evaluation of the VIIRS BRDF, Albedo and NBAR Products Suite and an Assessment of Continuity with the Long Term MODIS Record

Bidirectional Reflectance Distribution Function (BRDF) model parameters, Albedo quantities, and Nadir BRDF Adjusted Reflectance (NBAR) products derived from the Visible Infrared Imaging Radiometer Suite (VIIRS), on the Suomi-NPP (National Polar-orbiting Partnership) satellite are evaluated with spatially representative in situ tower albedometer measurements and through comparison with the MODerate Resolution Imaging Spectroradiometer (MODIS) long term record. White Sky Albedo (WSA), Black Sky Albedo (BSA), NBAR, and Quality Assurance (QA) results show that the VIIRS algorithm is performing well at the global scale and is able to provide global data products comparable with the heritage MODIS (with an absolute bias of 0.0069 for shortwave broadband WSA) despite the spectral, angular, and effective spatial resolution differences between the two sensors. Both VIIRS and MODIS albedo are shown to agree well with in situ albedo measurements at a number of spatially representative sites. This evaluation provides confidence that the high quality, daily VIIRS BRDF model parameters, Albedo, and NBAR products will be able to provide the long term continuity required by the modeling and monitoring communities.

VIIRS↗