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Li, Yang

Publications and source records attributed to Li, Yang.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

miR-92a is upregulated in cervical cancer and promotes cell proliferation and invasion by targeting FBXW7

MicroRNAs (miRNAs) are involved in the cervical carcinogenesis and progression. In this study, we investigated the role of miR-92a in progression and invasion of cervical cancer. MiR-92a was significantly upregulated in cervical cancer tissues and cell lines. Overexpression of miR-92a led to remarkably enhanced proliferation by promoting cell cycle transition from G1 to S phase and significantly enhanced invasion of cervical cancer cells, while its knockdown significantly reversed these cellular events. Bioinformatics analysis suggested F-box and WD repeat domain-containing 7 (FBXW7) as a novel target of miR-92a, and miR-92a suppressed the expression level of FBXW7 mRNA by direct binding to its 3′-untranslated region (3′UTR). Expression of miR-92a was negatively correlated with FBXW7 in cervical cancer tissues. Furthermore, Silencing of FBXW7 counteracted the effects of miR-92a suppression, while its overexpression reversed oncogenic effects of miR-92a. Together, these findings indicate that miR-92a acts as an onco-miRNA and may contribute to the progression and invasion of cervical cancer, suggesting miR-92a as a potential novel diagnostic and therapeutic target of cervical cancer. - Highlights: • miR-92a is elevated in cervical cancer tissues and cell lines. • miR-92a promotes cervical cancer cell proliferation, cell cycle transition from G1 to S phase and invasion. • FBXW7 is a direct target of miR-92a. • FBXW7 counteracts the oncogenic effects of miR-92a on cervical cancer cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Optimizations of spin-exchange relaxation-free magnetometer based on potassium and rubidium hybrid optical pumping

The hybrid optical pumping atomic magnetometers have not realized its theoretical sensitivity, the optimization is critical for optimal performance. The optimizations proposed in this paper are suitable for hybrid optical pumping atomic magnetometer, which contains two alkali species. To optimize the parameters, the dynamic equations of spin evolution with two alkali species were solved, whose steady-state solution is used to optimize the parameters. The demand of the power of the pump beam is large for hybrid optical pumping. Moreover, the sensitivity of the hybrid optical pumping magnetometer increases with the increase of the power density of the pump beam. The density ratio between the two alkali species is especially important for hybrid optical pumping magnetometer. A simple expression for optimizing the density ratio is proposed in this paper, which can help to determine the mole faction of the alkali atoms in fabricating the hybrid cell before the cell is sealed. The spin-exchange rate between the two alkali species is proportional to the saturated density of the alkali vapor, which is highly dependent on the temperature of the cell. Consequently, the sensitivity of the hybrid optical pumping magnetometer is dependent on the temperature of the cell. We proposed the thermal optimization of the hybrid cell for a hybrid optical pumping magnetometer, which can improve the sensitivity especially when the power of the pump beam is low. With these optimizations, a sensitivity of approximately 5 fT/Hz{sup 1/2} is achieved with gradiometer arrangement.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Griffiths phase, spin-phonon coupling, and exchange bias effect in double perovskite Pr{sub 2}CoMnO{sub 6}

The ceramic Pr{sub 2}CoMnO{sub 6} of double perovskite structure is prepared by a solid-state reaction and the magnetic properties, phonon behaviors are studied in detail. Two ferromagnetic transitions at T{sub C1} ∼ 172 K and T{sub C2} ∼ 140 K are observed in the temperature-dependent magnetization curves, respectively. Furthermore, a detail analysis on the magnetic susceptibility reveals that a short-range ferromagnetic clustered state exists above T{sub C1}, which can be well described as the Griffiths phase with a well-defined Griffiths temperature T{sub G} ∼ 210 K. The presence of the B-site antisite defects is considered to contribute to the observed Griffiths singularity. Temperature-dependent Raman scattering experiment reveals an obvious softening of the phonon mode involving stretching vibrations of the (Co/Mn)O{sub 6} octahedra in FM temperature regions, indicating a close correlation between magnetism and lattice in Pr{sub 2}CoMnO{sub 6}. On the other hand, it is found that the phonon softening extends up to T{sub G}, which further confirms the preformation of the short-range ferromagnetic clusters up to T{sub G}. Moreover, the field-cooling magnetic hysteresis loop reveals that exchange bias phenomena is present, which is supposed to origin from the exchange coupling between Co/Mn ordered ferromagnetic phases with antiferromagnetic antiphase boundaries caused by the partially Co/Mn antisite disorders. These findings give a systematic understanding on the magnetic interaction in Pr{sub 2}CoMnO{sub 6} which is closely related to the lattice and atomic distribution, and add special interest for application of this material.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Set statistics in conductive bridge random access memory device with Cu/HfO{sub 2}/Pt structure

The switching parameter variation of resistive switching memory is one of the most important challenges in its application. In this letter, we have studied the set statistics of conductive bridge random access memory with a Cu/HfO{sub 2}/Pt structure. The experimental distributions of the set parameters in several off resistance ranges are shown to nicely fit a Weibull model. The Weibull slopes of the set voltage and current increase and decrease logarithmically with off resistance, respectively. This experimental behavior is perfectly captured by a Monte Carlo simulator based on the cell-based set voltage statistics model and the Quantum Point Contact electron transport model. Our work provides indications for the improvement of the switching uniformity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Microscopic mechanism of electron transfer through the hydrogen bonds between carboxylated alkanethiol molecules connected to gold electrodes

The atomic structure and the electron transfer properties of hydrogen bonds formed between two carboxylated alkanethiol molecules connected to gold electrodes are investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. Three types of molecular junctions are constructed, in which one carboxyl alkanethiol molecule contains two methylene, –CH{sub 2}, groups and the other one is composed of one, two, or three –CH{sub 2} groups. Our calculations show that, similarly to the cases of isolated carboxylic acid dimers, in these molecular junctions the two carboxyl, –COOH, groups form two H-bonds resulting in a cyclic structure. When self-interaction corrections are explicitly considered, the calculated transmission coefficients of these three H-bonded molecular junctions at the Fermi level are in good agreement with the experimental values. The analysis of the projected density of states confirms that the covalent Au–S bonds localized at the molecule-electrode interfaces and the electronic coupling between –COOH and S dominate the low-bias junction conductance. Following the increase of the number of the –CH{sub 2} groups, the coupling between –COOH and S decreases deeply. As a result, the junction conductance decays rapidly as the length of the H-bonded molecules increases. These findings not only provide an explanation to the observed distance dependence of the electron transfer properties of H-bonds, but also help the design of molecular devices constructed through H-bonds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Influence of insulating coating on aluminum wire explosions

Single wire explosions are widely used in understanding the early stages of z-pinch experiments. This paper presents a serial of experiments conducted on the pulse power generator with ∼1 kA peak current and ∼10 ns rising time in Xi'an Jiao Tong University. Polyimide coated aluminum wires and uncoated ones were tested under three different voltages to analyze the effect of insulating coating. Experimental results showed that insulating coating can increase the energy deposition 10%∼30% in aluminum wires by delaying the voltage collapse and raising the maximum load resistance. The substantial energy deposition resulted in about 20% faster expansion rates for coated wires. Experimental evidence that plasma channel shunts the current from the wire core was observed by streak camera and schlieren graphs. This paper also briefly discussed the influence of nonuniform coating on the morphology of wire expansion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Influence of post-deposition annealing on interfacial properties between GaN and ZrO{sub 2} grown by atomic layer deposition

Influence of post-deposition annealing on interfacial properties related to the formation/annihilation of interfacial GaO{sub x} layer of ZrO{sub 2} grown by atomic layer deposition (ALD) on GaN is studied. ZrO{sub 2} films were annealed in N{sub 2} atmospheres in temperature range of 300 °C to 700 °C and analyzed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that Ga-O bond to Ga-N bond area ratio decreases in the samples annealed at temperatures lower than 500 °C, which could be attributed to the thinning of GaO{sub x} layer associated with low surface defect states due to “clean up” effect of ALD-ZrO{sub 2} on GaN. However, further increase in annealing temperature results in deterioration of interface quality, which is evidenced by increase in Ga-O bond to Ga-N bond area ratio and the reduction of Ga-N binding energy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

A setup for simultaneous measurement of infrared spectra and light scattering signals: Watching amyloid fibrils grow from intact proteins

A setup for the simultaneous measurement of mid-infrared spectra and static light scattering is described that can be used for the analysis of the formation of nanoscale and microscopic aggregates from smaller molecules to biopolymers. It can be easily integrated into sample chambers of infrared spectrometers or combined with laser beams from tunable infrared lasers. Here, its use for the analysis of the formation of amyloid fibrils from intact proteins is demonstrated. The formation of amyloid fibrils or plaques from proteins is a widespread and pathogenetic relevant process, and a number of diseases are caused and correlated with the deposition of amyloid fibrils in cells and tissues. The molecular mechanisms of these transformations, however, are still unclear. We report here the simultaneous measurement of infrared spectra and static light scattering for the analysis of fibril formation from egg-white lysozyme. The transformation of the native form into non-native forms rich in β-sheet structure is measured by analysis of the amide I spectral region in the infrared spectra, which is sensitive for local structures. At the same time, light scattering signals at forward direction as well as the forward/backward ratio, which are sensitive for the number of scattering centers and their approximate sizes, respectively, are collected for the analysis of fibril growth. Thermodynamic and kinetic parameters as well as mechanistic information are deduced from the combination of the two complementary techniques.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Band alignment between GaN and ZrO{sub 2} formed by atomic layer deposition

The band alignment between Ga-face GaN and atomic-layer-deposited ZrO{sub 2} was investigated using X-ray photoelectron spectroscopy (XPS). The dependence of Ga 3d and Zr 3d core-level positions on the take-off angles indicated upward band bending at GaN surface and potential gradient in ZrO{sub 2} layer. Based on angle-resolved XPS measurements combined with numerical calculations, valence band discontinuity ΔE{sub V} of 1 ± 0.2 eV and conduction band discontinuity ΔE{sub C} of 1.2 ± 0.2 eV at ZrO{sub 2}/GaN interface were determined by taking GaN surface band bending and potential gradient in ZrO{sub 2} layer into account.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Method and system for capturing carbon dioxide and/or sulfur dioxide from gas stream

The present invention provides a system for capturing CO.sub.2 and/or SO.sub.2, comprising: (a) a CO.sub.2 and/or SO.sub.2 absorber comprising an amine and/or amino acid salt capable of absorbing the CO.sub.2 and/or SO.sub.2 to produce a CO.sub.2- and/or SO.sub.2-containing solution; (b) an amine regenerator to regenerate the amine and/or amino acid salt; and, when the system captures CO.sub.2, (c) an alkali metal carbonate regenerator comprising an ammonium catalyst capable catalyzing the aqueous alkali metal bicarbonate into the alkali metal carbonate and CO.sub.2 gas. The present invention also provides for a system for capturing SO.sub.2, comprising: (a) a SO.sub.2 absorber comprising aqueous alkali metal carbonate, wherein the alkali metal carbonate is capable of absorbing the SO.sub.2 to produce an alkali metal sulfite/sulfate precipitate and CO.sub.2.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

TiO{sub 2} nanobelts photocatalysts decorated with Bi{sub 2}WO{sub 6} nanocrystals: Preparation and enhanced photocatalytic activity

Highlights: • TiO{sub 2} nanobelts decorated with Bi{sub 2}WO{sub 6} nanocrystals have been prepared. • The introduction of Bi{sub 2}WO{sub 6} nanocrystals can induce red-shift of absorption edge. • The Bi{sub 2}WO{sub 6}/TiO{sub 2} composites show higher photocatalytic activity than TiO{sub 2} nanobelts. • The Bi{sub 2}WO{sub 6}/TiO{sub 2} composites have long-time recyclable ability of photodegradation. - Abstract: In this paper, the controllable preparation of one-dimensional TiO{sub 2} nanobelts decorated with Bi{sub 2}WO{sub 6} nanocrystals based on Ti foils was reported using two-step hydrothermal treatment method. X-ray photoelectron spectroscopy measurement results exhibited the binding energy changes of Ti and O elements, implying the strong adhesion of Bi{sub 2}WO{sub 6} nanocrystals onto the surface of TiO{sub 2} nanobelts. The ultraviolet–visible (UV–vis) absorption spectra showed that the introduction of Bi{sub 2}WO{sub 6} nanocrystals could induce the red-shift of absorption edge and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and help to improve the photocatalytic degradation efficiency. The photocatalytic experiment results revealed that Bi{sub 2}WO{sub 6}/TiO{sub 2} composites possess higher photocatalytic activities toward methyl orange than pure TiO{sub 2} nanobelts. The degradation efficiency of 90% after 5 cycles indicated that the as-prepared composite photocatalysts exhibited excellent long-time recyclable ability for the degradation of contaminants.

36 MATERIALS SCIENCE↗
DOE OSTI2014

In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect

A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz{sup 1/2}, which was mainly dominated by the noise of the magnetic shield.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Investigation on multi-variable decoupled temperature control system for enamelling machine with heated air circulation

A lots of problems may occur frequently when controlling the temperature of the enamelling machine oven in the real industrial process, such as multi-variable coupled problem. an experimental rig with triple inputs and triple outputs was devised and a simulation modeling was established accordingly in this study,. the temperature control system based on the feedforward compensation algorithm was proposed. Experimental results have shown that the system is of high efficiency, good stability and promising application.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Preparation and thermal stability of the spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} core–shell nanoparticles

The spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} core–shell nanoparticles (NPs) are prepared via hydrothermal synthesis and modified Stöber method. During these processes, shell thicknesses could be easily adjusted by the amount of tetraethylorthosilicate (TEOS), and the formation of core-free SiO{sub 2} could be effectively avoided. The structures and compositions of α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are investigated by transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–vis) absorption spectroscopy. These results reveal that the α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs with certain sizes are monodisperse and homogeneous. To estimate the thermal stability, the α-Fe{sub 2}O{sub 3}, α-Fe{sub 2}O{sub 3}@SiO{sub 2} and SiO{sub 2} NPs are annealed at 600, 800 and 1000 °C for 1 h under air atmosphere, respectively. Furthermore, the stabilities of these NPs are confirmed by thermal analysis methods. The structure and shape stabilities of these as-prepared α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are investigated by XRD and scanning electron microscope (SEM). -- Graphical abstract: Schematic of preparation of the monodisperse spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} nanoparticles (NPs). Highlights: • The spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} nanoparticles (NPs) are successfully prepared by hydrothermal synthesis and modified Stöber method. • Optical properties are estimated and calculated by UV vis absorption spectrum. • Thermal stability of the α-Fe{sub 2}O{sub 3}, α-Fe{sub 2}O{sub 3}@SiO{sub 2} and SiO{sub 2} NPs are compared and analyzed by the SEM technique. • The structural changes of α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are measured by XRD measurement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

GaAs buffer layer technique for vertical nanowire growth on Si substrate

Gold catalyzed vapor-liquid-solid method is widely applied to III–V nanowire (NW) growth on Si substrate. However, the easy oxidation of Si, possible Si contamination in the NWs, high defect density in the NWs, and high sensitivity of the NW morphology to growth conditions largely limit its controllability. In this work, we developed a buffer layer technique by introducing a GaAs thin film with predefined polarity as a template. It is found that samples grown on these buffer layers all have high vertical NW yields in general, due to the single-orientation of the buffer layers. Low temperature buffer with smoother surface leads to highest yield of vertical NWs, while high temperature (HT) buffer with better crystallinity results in perfect NW quality. The defect-free property we observed here is very promising for optoelectronic device applications based on GaAs NW. Moreover, the buffer layers can eliminate Si contamination by preventing Si-Au alloy formation and by increasing the thickness of the Si diffusion barrier, thus providing more flexibility to vertical NW growth. The buffer layer technique we demonstrated here could be easily extended to other III-V on Si system for electronic and photonic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Defect reduction in Si-doped Al{sub 0.45}Ga{sub 0.55}N films by SiN{sub x} interlayer method

The dislocation density in AlGaN epitaxial layers with Al content as high as 45% grown on sapphire substrates has been effectively reduced by introducing an in-situ deposited SiN{sub x} nanomask layer in this study. By closely monitoring the evolution of numerous material properties, such as surface morphology, dislocation density, photoluminescence, strain states, and electron mobility of the Si-Al{sub 0.45}Ga{sub 0.55}N layers as the functions of SiN{sub x} interlayer growth time, the surface coverage fraction of SiN{sub x} is found to be a crucial factor determining the strain states and dislocation density. The dependence of the strain states and the dislocation density on the surface coverage fraction of SiN{sub x} nanomask supports the very different growth models of Al-rich AlGaN on SiN{sub x} interlayer due to the reduced nucleation selectivity compared with the GaN counterpart. Compared with GaN, which can only nucleate at open pores of SiN{sub x} nanomask, Al-rich AlGaN can simultaneously nucleate at both open pores and SiN{sub x} covered areas. Dislocations will annihilate at the openings due to the 3D growth initiated on the opening area, while 2D growth mode is preserved on SiN{sub x} and the threading dislocations are also preserved. During the following growth process, lateral overgrowth will proceed from the Al{sub 0.45}Ga{sub 0.55}N islands on the openings towards the regions covered by SiN{sub x}, relaxing the compressive strain and bending the dislocations at the same time.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Preparation and properties of hexagonal boron nitride fibers used as high temperature membrane filter

Graphical abstract: - Highlights: • h-BN fibers were successfully fabricated using H{sub 3}BO{sub 3} and C{sub 3}H{sub 6}N{sub 6} as raw materials. • The obtained BN fibers were polycrystalline and uniform in morphology. • It exhibited good oxidation resistance and low thermal expansion coefficient. - Abstract: Hexagonal boron nitride fibers were synthesized via polymeric precursor method using boric acid (H{sub 3}BO{sub 3}) and melamine (C{sub 3}H{sub 6}N{sub 6}) as raw materials. The precursor fibers were synthesized by water bath and BN fibers were prepared from the precursor at 1873 K for 3 h in flowing nitrogen atmosphere. The crystalline phase and microstructures of BN fibers were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. The results showed that h-BN fibers with uniform morphology were successfully fabricated. The well-synthesized BN fibers were polycrystalline with 0.4–1.5 μm in diameter and 200–500 μm in length. The as-prepared samples exhibited good oxidation resistance and low thermal expansion coefficient at high temperature.

36 MATERIALS SCIENCE↗