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NMR experiments reveal a mechanism of syngas conversion in which CO reacts with OCH3 on the oxide surface, generating ketene intermediates, which can either form acetate or diffuse into zeolite.

The low-temperature hydrogenation of CO2 to methanol is of great significance for the recycling of this greenhouse gas to valuable products, however, it remains a great challenge due to the trade-off between catalytic activity and selectivity. Here, we report that CO2 can dissociate at sulfur vacancies in MoS2 nanosheets to yield surface-bound CO and O at room temperature, thus enabling a highly efficient low-temperature hydrogenation of CO2 to methanol. Multiple in situ spectroscopic and microscopic characterizations combined with theoretical calculations demonstrated that in-plane sulfur vacancies drive the selective hydrogenation of CO2 to methanol by inhibiting deep hydrogenolysis to methane, whereas edge vacancies facilitate excessive hydrogenation to methane. At 180 °C, the catalyst achieved a 94.3% methanol selectivity at a CO2 conversion of 12.5% over the in-plane sulfur vacancy-rich MoS2 nanosheets, which notably surpasses those of previously reported catalysts. This catalyst exhibited high stability for over 3,000 hours without any deactivation, rendering it a promising candidate for industrial application. The catalytic hydrogenation of CO2 to methanol is a crucial reaction for the recycling of this greenhouse gas, although the selection and related performance of commercial catalysts is still limited. Now, the authors introduce sulfur vacancy-rich MoS2 nanosheets as a superior catalyst for this process, rivalling the commercial benchmark system.

Heteronuclear dipolar coupling is indispensable in revealing vital information related to the molecular structure and dynamics, as well as intermolecular interactions in various solid materials. Although numerous approaches have been developed to selectively reintroduce heteronuclear dipolar coupling under MAS, most of them lack universality and can only be applied to limited spin systems. Herein, we introduce a new and robust technique dubbed phase modulated rotary resonance (PMRR) for reintroducing heteronuclear dipolar couplings while suppressing all other interactions under a broad range of MAS conditions. The standard PMRR requires the radiofrequency (RF) field strength of only twice the MAS frequency, can efficiently recouple the dipolar couplings with a large scaling factor of 0.50, and is robust to experimental imperfections. Moreover, the adjustable window modification of PMRR, dubbed wPMRR, can improve its performance remarkably, making it well suited for the accurate determination of dipolar couplings in various spin systems. The robust performance of such pulse sequences has been verified theoretically and experimentally via model compounds, at different MAS frequencies. The application of the PMRR technique was demonstrated on the H-ZSM-5 zeolite, where the interaction between the Bronsted acidic hydroxyl groups of H-ZSM-5 and the absorbed trimethylphosphine oxide (TMPO) were probed, revealing the detailed configuration of super acid sites.

Aims Phospholipase A2 (PLA2 ) is a diverse superfamily that hydrolyzes fatty acyl ester bonds at the sn-2 position of phospholipids. The correlation between phospholipid metabolism and the anabolism of neutral lipids remains unclear in yeasts. This study aims to explore the effects of PLA2 on lipid accumulation in the oleaginous yeast Yarrowia lipolytica. Methods and results This study identified an actively expressed phospholipase A2 gene (PLA2-3, YAIL0_E16060g) in Y. lipolytica by quantitative PCR analysis. The gene PLA2-3 was disrupted in the strain po1gΔKu70 by homologous recombination and in the strain po1g-G3 by a CRISPR-Cas9 system, which caused an increase in stress sensitivity while the cell growth was not altered under fermentative conditions. Lipid production was performed in both flasks and bioreactors. The results showed that the lipid titre and lipid content were improved over 25% and 8-30%, respectively, in PLA2-3 disrupted strains compared to the controls. Conclusions Disruption of the phospholipase PLA2-3 gene could effectively improve lipid production in Y. lipolytica. Significance and impact of the study This study presented a strategy on improving the lipid production of oleaginous yeasts and a similar strategy might be used in other oleaginous microbes.

Remarkable progress has been made in dissecting the molecular mechanisms involved in iron (Fe) homeostasis in plants, especially the identification of key transporter and transcriptional regulatory networks. But how the protein activity of these master players is regulated by Fe status remains underexplored. Recent studies show that major players toggle switch their properties by protein phosphorylation under different Fe conditions and consequently control the signaling cascade and metabolic adjustment. Moreover, Fe deficiency causes changes of multiple kinases and phosphatases. Here, we discuss how these findings highlight the emergence of the protein phosphorylation-dependent regulation for rapid and precise responses to Fe status to attain Fe homeostasis. Further studies will be needed to fully understand the regulation of these intricate networks.

We theoretically study the scattering behavior of spin waves (SWs) at the interface of an antiferromagnetically coupled (AFMC) heterojunction. It is shown that the SWs passing through the interface are evanescent and the incident waves are all reflected back, demonstrating a magnetization-dependent magnon blocking effect in this structure. We also analytically derive the expressions for the decay length of the evanescent waves (EWs). The theoretical result indicates that with the increase of the spin-wave (SW) frequency, the decay length decreases and the EWs are more concentrated at the interface, showing a magnonic skin effect (MSE) which is similar to the skin effect of electromagnetic waves. Furthermore, a positive magnonic Goos-H\"anchen shift (MGHS) of the reflected waves is also predicted. It can be understood by an effective reflection interface shift induced by the nonzero decay length of the EWs. The results of micromagnetic simulations are consistent well with all the theoretical findings. Based on the above findings, we also propose a magnon valve without spacers, which shows 100% on-off ratio for magnons. Our work provides insights into SW transmissions in the system of AFMC heterostructures and will serve as a promising tool for future magnonic devices.

Mordenite (MOR) zeolite is known to possess a 12-membered ring (12 MR) and 8 MR channels, which are interconnected by 8 MR side pockets. Hyperpolarization (HP) 129Xe NMR reveals a new Xe adsorption...

A comparative study of the adsorption and desorption processes of methanol in two kinds of nanochannels (i.e. MCM-41 and SWNTs) is performed by in situ continuous-flow laser-hyperpolarized 129Xe NMR. The high sensitivity and short acquisition time of hyperpolarized 129Xe allow for probing the molecular dynamics in a confined geometry under real working conditions. Hyperpolarized 129Xe NMR spectra indicate that the methanol adsorption behavior in nanochannels is determined by the characters of adsorption sites and that the methanol adsorption rate in the nanochannels of SWNTs is faster than in MCM-41. The experimental data shown in this work also indicate that there is a change in gas phase 129Xe NMR signal intensity during the adsorption and desorption of methanol in SWNTs. This may be because there is a strong depolarization of hyperpolarized 129Xe in SWNTs.

The discovery of two-dimensional (2D) van der Waals (vdW) intrinsic magnets has opened a promising avenue to design high-performance magnetic tunnel junctions (MTJs) based on 2D materials. In this work, using first-principles calculations, it is demonstrated that bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$ is intrinsically a magnetic semiconductor with intralayer ferromagnetic (FM) and interlayer antiferromagnetic (AFM) couplings and the interlayer AFM coupling in bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$ is independent on the stacking orders. Moreover, using the nonequilibrium Green's function combined with density functional theory, it is found that due to the large difference between interlayer AFM and FM states of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier, the conductance of spin filter (SF) vdW MTJs based on the graphene/bilayer $\mathrm{Co}{\mathrm{Br}}_{2}$/graphene heterostructure for the interlayer FM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier is about 25 times that for the interlayer AFM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier. Consequently, a high tunneling magnetoresistance (TMR) ratio of $2420%$ is achieved in this SF-vdW MTJ at zero bias. In particular, because the current for the interlayer FM state of the $\mathrm{Co}{\mathrm{Br}}_{2}$ barrier rapidly increases with the increase of bias voltage, a giant TMR ratio of up to about $38\phantom{\rule{0.16em}{0ex}}000%$ can be achieved in this SF-vdW MTJ at 0.2-V bias. Our results suggest that SF-vdW MTJs formed by the interlayer AFM barrier with variable conductivity hold great potential for developing vdW MTJs with a high TMR ratio.

We theoretically investigate the transmission of exchange-dominated spin waves in a one-dimensional magnonic crystal (MC) with a periodic exchange bias field. By recasting the Landau-Lifshitz-Gilbert equation into an effective Schr\"odinger equation and establishing spin-wave functions, it is found that MCs with upward (up) and downward (down) magnetization, respectively, correspond to the rectangular $N$-fold barriers and wells for magnons. The broadband transmission spectra in up and down states are systematically investigated. We show the phenomena of the magnon resonant transmission in both states and calculate the resonant transmission wave functions, which are related to the magnon density. Our results also show a transmission spectra shift effect (TSSE) between up and down states, which is found to be general in this system. Furthermore, the TSSE is useful to design a type of magnon valve, the magnonic-crystal-based magnon valve (MCMV), which has a large on/off ratio and bandwidth. By high-throughput screening, 125 000 groups of parameters of the MC are calculated, and 1948 parameter groups of high-performance MCMVs are screened out. Our work clarifies the physical details of the exchange-dominated spin-wave transmission in rectangular $N$-fold barriers and wells and also provides a promising route for designing novel magnonic devices.

A quasi-coherent mode (QCM) near the plasma edge is characterized experimentally by measuring the density fluctuation via a poloidal correlation reflectometer (PCR) in Wendelstein 7-X. This QCM frequency descends from 25 kHz near the separatrix to 10 kHz as the cutoff position penetrates toward the core. A similar mode structure is also observed in the spectra of electron cyclotron emission edge channels and Mirnov coil signals, which shows a clear correlation with respect to the PCR measurement. The mode evaluation yields a range for the poloidal mode number of , and for the normalized mode scale , which suggest a drift type instability. The QCM structure appears in the standard and narrow-mirror configurations (both with the rotational transform in the boundary), but is absent in the high- configuration (boundary ). The impact of plasma parameters on the QCM is discussed. It is observed that the QCM frequency and amplitude can be affected by the edge magnetic topology and plasma parameters. The shifts upward during the negative and non-stellarator-symmetric control coil current scans, which may be attributed to the effect of the shear, Er, and ne in the plasma edge region.

A fast NMR data acquisition strategy is explored to detect and characterize carbocations on solid zeolites., Acidic zeolites are porous aluminosilicates used in a wide range of industrial processes such as adsorption and catalysis. The formation of carbocation intermediates plays a key role in reactivity, selectivity and deactivation in heterogeneous catalytic processes. However, the observation and determination of carbocations remain a significant challenge in heterogeneous catalysis due to the lack of selective techniques of sufficient sensitivity to detect their low concentrations. Here, we combine 13C isotopic enrichment and efficient dynamic nuclear polarization magic angle spinning nuclear magnetic resonance spectroscopy to detect carbocations in zeolites. We use two dimensional 13C–13C through-bond correlations to establish their structures and 29Si–13C through-space experiments to quantitatively probe the interaction between multiple surface sites of the zeolites and the confined hydrocarbon pool species. We show that a range of various membered ring carbocations are intermediates in the methanol to hydrocarbons reaction catalysed by different microstructural β-zeolites and highlight that different reaction routes for the formation of both targeted hydrocarbon products and coke exist. These species have strong van der Waals interaction with the zeolite framework demonstrating that their accumulation in the channels of the zeolites leads to deactivation. These results enable understanding of deactivation pathways and open up opportunities for the design of catalysts with improved performances.

Summary Direct conversion of methane to high-value-added chemicals is a major challenge in catalysis, which usually requires high-energy input to overcome the reaction barrier. We report that graphene-confined single Fe atoms can be used as an efficient non-precious catalyst to directly convert methane to C1 oxygenated products at room temperature. A series of graphene-confined 3d transition metals (Mn, Fe, Co, Ni, and Cu) were screened, yet only single Fe atoms could catalyze the methane conversion. Combining in operando time-of-flight mass spectrometry, 13C nuclear magnetic resonance, and density functional theory calculations, we found that methane conversion proceeds on the O–FeN4–O active site along a radical pathway to produce CH3OH and CH3OOH first, and then the generated CH3OH can be further catalyzed to form HOCH2OOH and HCOOH at room temperature.

A multiple laser system for high-resolution Thomson scattering diagnostics has been developed in ASIPP. The system includes laser controller, high-energy lasers, transfer optics, focusing lens, and beam alignment system. Each Nd:YAG laser can be fired for measuring the electron temperature and density profiles periodically at 10 Hz, and consequently, four lasers can be fired alternately for an average measurement frequency of 40 Hz. In order to measure transient events, they will be fired in rapid succession, and produce a burst of pulses. After about one month trial running on the superconducting EAST tokamak, the system was proven to be capable of working well with improved time resolution. The system setup and analysis are described in detail, as well as the measurement capability, spatial and temporal resolutions ~7 mm and tens kilohertz, respectively. So as to monitor and adjust the laser beam, two beam position sensitive detectors are installed in the 40-m beam path. Finally, the experimental results are presented.

Metal ion doping is an effective way for improving the intrinsic properties of Na3V2(PO4)3. However, mechanistic exploration of metal ion doping in Na3V2(PO4)3, which is essential for the design and optimization of metal ion doping, is indistinct. To achieve an in-depth understanding of the mechanism of metal ion doping, Li ion doped Na3−xLixV2(PO4)3/C (x = 0, 0.01, 0.05, 0.1, 0.5, 0.7 and 1.0) compounds are synthesized. By utilizing DFT, NMR and Rietveld methods, the mechanism of Li/Na ion doping and rearrangement in the Na sites and Na ion insertion/extraction during electrochemical cycles are explored and identified. It is found that during the synthesis process, Li ions are inclined to enter mainly the Na2 sites in Na3V2(PO4)3 when the x value is low, but they will occupy the Na1 and Na2 sites simultaneously when x is high. Meanwhile, Li ions in the as-prepared Na3−xLixV2(PO4)3 compounds are reversibly replaced by Na ions during the idle state, due to the very small energy difference of the exchange between Li and Na ions. Furthermore, it is confirmed that there are more than two Na ions inserted/extracted during the charge–discharge process, resulting in the final extra specific capacity.

In order to improve the high temperature wear- and oxidation resistance of single crystal superalloy, NiCr-Cr3C2 coatings were vacuum brazed on the surface. Different weight ratios of Cr were added into the coatings to control the diffusion of Si and C into the base metal, which would be harmful to the base metal stability. The results show that, when no Cr was added into the coatings, a layer of Ni3Si phase at the interface and MC precipitates in base metal were produced. With the increase of the Cr addition, the coating/base metal interface was gradually purified. The Ni3Si layer and the MC precipitates disappeared when the Cr addition increased to 30 wt% and an interface was clearly presented with the γ′ phases on both sides epitaxially growing on some extent. After 200 thermal fatigue cycles, the total crack lengths were measured, which decreased with increasing Cr addition, indicating that the thermal fatigue resistance was improved.

Understanding the properties and behavior of water molecules in restricted geometries, such as the nanopores of rocks, is of interest for shale gas exploitation. We present herein ex situ and in situ nuclear magnetic resonance (NMR) studies on the effects of water on the adsorption and diffusion of methane in nanopores. Silica materials with one-dimensional pores of ZSM-22, MCM-41, and SBA-15, with pore sizes ranging from 0.5 to 6 nm, were chosen as models. Hyperpolarized (HP) 129Xe NMR results show that water adsorption does not affect the pore sizes of ZSM-22 and MCM-41 but reduces that of SBA-15. The presence of water suppresses methane adsorption; this suppression effect is stronger in smaller pores. The self-diffusion coefficients of methane within ZSM-22 and MCM-41 are not significantly influenced by the presence of water, as measured by 1H pulsed field gradient (PFG) NMR. However, within SBA-15, which has a pore size of 6 nm, the diffusion coefficient of methane increases as the amount of water adsorption increases, peaks, and then decreases to a constant value with further water adsorption. These experiments reveal the effects of the pore size and the presence of water on methane adsorption and diffusion in constrained spaces, which could have important implications for flow simulations of methane in shales.

The effects of the acid site in main channels of MOR zeolites on their product selectivity and deactivation in the MTO (methanol to olefin) reactions were investigated. The catalytic analysis demonstrates that the pyridine modified MOR zeolite yielded high selectivity (> 65.3%) of C2=-C4=, although the conversion dropped from 100% to 54%. Furthermore, both the catalytic lifetime of MOR and the stability of yielding the lower olefins were increased from less than 30 min to more than 120 min after the modification with pyridine. 1H MAS NMR on MOR and modified MOR shows that the acid sites in main channel do not benefit the productivity of lower olefins and catalysts lifetime. It can be concluded from ex-situ 13C CP MAS NMR that the deposit species during the MTO reaction depend on the pore sizes, and the formation of large alkyl aromatic species more likely occurs in the 12-ring main channels rather than the 8-ring side pocket.

With increasing concern about the environmental impact of shale gas exploitation, nonaqueous fracturing with carbon dioxide has emerged as a promising alternative to increase gas production and, at the same time, to store large amounts of CO2. The key process of CH4 displacement by CO2 is worth a systematic investigation from aspects of both experiment and simulation. In this work, the CH4 and CO2 displacement was studied with in situ 13C NMR in the pores of silica (SBA-15), which were functionalized with organic groups such as phenyl and cyclohexyl, in order to model the organic matter in shale with different aromaticity. Due to the stronger adsorption strength and higher capacity of CO2 in SBA-15, CH4 can be easily stripped out of the pores by CO2, while the reverse process to displace CO2 with CH4 is not effective. Even though the displacement effect in the pores of SBA-15 with a higher aromaticity is relatively better at room temperature, the superiority is eliminated by high temperature. Furthermore,...

A comparative study of the adsorption and desorption processes of methanol in two kinds of nanochannels (i.e. MCM-41 and SWNTs) is performed by in situ continuous-flow laser-hyperpolarized 129Xe NMR. The high sensitivity and short acquisition time of hyperpolarized 129Xe allow for probing the molecular dynamics in a confined geometry under real working conditions. Hyperpolarized 129Xe NMR spectra indicate that the methanol adsorption behavior in nanochannels is determined by the characters of adsorption sites and that the methanol adsorption rate in the nanochannels of SWNTs is faster than in MCM-41. The experimental data shown in this work also indicate that there is a change in gas phase 129Xe NMR signal intensity during the adsorption and desorption of methanol in SWNTs. This may be because there is a strong depolarization of hyperpolarized 129Xe in SWNTs.

13 C–13C through-bond NMR correlation experiments reveal the stabilization of different carbenium ion intermediates in two zeolites possessing identical CHA topology (H-SAPO-34 and H-SSZ-13) during the methanol to olefins reaction.

In this work, we have studied the role of the 12-ring channel of mordenite in DME carbonylation. Upon modification with pyridine, the catalytic lifetime of mordenite in DME carbonylation was prolonged dramatically although its activity decreased slightly and the induction period increased. 1H MAS NMR and PFG-NMR results demonstrated that the acid quantity decreased after pyridine was adsorbed, and the self-diffusion coefficient of CH4 decreased with the increase in pyridine quantity in the 12-ring channel. 129Xe NMR results reveal that Xe atoms are preferentially adsorbed in an 8-ring side pocket at low pressure; xenon can enter the 8-ring side pocket at high temperature through the 12-ring channels only. From these results, the function of the 12-ring with respect to the reaction rate is explored and a transfer path of reactants/products is proposed.

Shale gas, which was recently discovered with a large reserve, has invoked wide interest as an alternative energy resource of natural gas. However, little is known about the molecular properties of shale gas (mainly methane) confined in the nanopores of shale, such as their diffusivity, which is essential for its exploitation and utilization. We study here the diffusivity of methane using 1H pulsed field gradient (PFG) NMR and theoretical modeling. Following analysis of the physicochemical properties of shale, a well-ordered mesoporous silica material (SBA-15) modified with organic functional groups is employed to model the mesopores observed in the shale and to study the fundamental behavior of shale gas. The results demonstrate that methane moves faster in the pores modified with the aromatic phenyl groups than those with nonaromatic cyclohexyl groups, suggesting a higher diffusivity of methane with increasing maturity of shale.

High field quantitative 27Al single pulse (SP) MAS NMR combined with temperature programmed desorption (TPD) of ethanol is used to study the surface of γ-Al2O3 during phase transformation processes induced by calcination in the temperature range of 500–1300 °C. Following ethanol adsorption, ethylene is generated during TPD with a desorption temperature above 200 °C. The amount of ethylene decreases monotonically with increasing calcination temperature prior to TPD. Significantly, 27Al SP MAS NMR reveals that the amount of penta-coordinated Al3+ ions also decreases with increasing calcination temperature. A quantitative (within experimental error) correlation between the amount of penta-coordinated Al3+ ions and the amount of strongly adsorbed ethanol molecules (i.e., the ones that convert to ethylene during TPD) is obtained. These results provide good evidence for a proposal that the penta-coordinated aluminum sites are the catalytic active sites on alumina surfaces during ethanol dehydration reaction across the entire course of γ-to-α Al2O3 phase transformations.

Water assisted phase transformation process from crystalized AlPO4-5 to AlPO4-tridymite was studied by the combination of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and in situ multinuclear MAS NMR. It is found that water first activates the residue amorphous aluminophosphate in crystalized AlPO4-5 sample through hydrolysis and condensation reactions. Then the activated aluminophosphate species reassemble into AlPO4-tridymite crystalline. Meanwhile, AlPO4-5 transforms into orthorhombic phase during heating process. With further crystallization of AlPO4-tridymite, the amorphous phase is gradually consumed, and mass transportation between AlPO4-5 and AlPO4-tridymite is established through gradually amorphization of AlPO4-5. Finally, most of the AlPO4-5 transforms into the thermodynamically stable dense phase AlPO4-tridymite.

Magnetic tunneling junctions with Co 40 Fe 40 B 20 /Co 70.5 Fe 4.5 Si 15 B 10 composite free layer have been fabricated and annealed at different temperatures to obtain the highest tunneling magnetoresistance. The field and temperature dependences of the low frequency noise have been measured to understand the origin of noise. The random telegraph noise has been observed at low magnetic field, and the corresponding fluctuating moment is estimated to be 4.8×10 5 μ B with an effective area of 240 nm 2 . The dependence of noise on temperature was coincident with the thermally activated kinetics model above 30 K while it deviated from this model below 30 K. Studying the origin of the low frequency noise is helpful to reduce the noise level in MTJs.

The edge localized mode (ELM) has been mitigated by n=1 resonant magnetic perturbation (RMP) in EAST tokamak. The turbulence characteristics and transport during the ELM mitigation have been measured by a series of diagnostics. The edge coherent mode (ECM) with a frequency about 25 kHz almost disappears when ELM is mitigated. The scrape-off layer (SOL) radial turbulent transport is measured by a four-tip Langmuir probe mounted on the manipulator at the outer midplane, exhibiting a strong enhancement of outward particle during the ELM mitigation in the SOL region (3-25 mm outside the LCFS). This enhanced outward radial transport is mainly driven by the low frequency turbulence (

An ordinary-mode polarized multi-channel correlation reflectometer has been developed on the Experimental Advanced Superconducting Tokamak (EAST). The system with four different probing frequencies (i.e., 20.4 GHz, 24.8 GHz, 33 GHz, and 40 GHz) and two poloidally spaced receiving antennas can realize both the radial correlation measurement and the poloidal correlation measurement. These diagnostics focus on the measurement of density fluctuation in the pedestal region to investigate the turbulence transport and H-mode physics on EAST. In this article, the system hardware design, the key component tests, and the system performance are shown in detail.

In the first experimental campaign of Wendelstein 7-X (W7-X), a combined probe head mounted on the multi-purpose manipulator has been used to measure the scrape-off layer (SOL) turbulence characteristics. The preliminary experimental results are summarized to illustrate the SOL turbulence properties in the limiter configuration on W7-X. In a standard limiter configuration, significant electrostatic fluctuations can be found in the near SOL, and the dominant frequency of fluctuation power is below 100 kHz. The auto-correlation spectrum power law decay factor is α ≈ −1 below 40 kHz and α ≈ –2 between 50 and 200 kHz. A broadband spectrum appears between 240 and 380 kHz with a low spectral power density, but a high cross-correlation coefficient. The statistical characteristics of turbulence are calculated by the two-point cross-correlation technique. A clear poloidal dispersion relation is found in the spectrum S(kθ, f), propagating along the ion diamagnetic drift direction with a group velocity (below 100 kHz) about 0.56 km/s in the near SOL in the laboratory frame. The poloidal correlation length is around 5–10 mm in SOL. The turbulence phase velocity is about 0.5–1 km/s when close to the last closed flux surface, which is comparable with the poloidal E × B drift speed.

SiO2 supported Pt–Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin–lattice relaxation of Q4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q3 species, which are in close contact with the paramagnetic nickel centers, are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. Howe...

A series of phosphates is investigated as additives to improve the stability of the electrolyte for vanadium flow battery (VFB). Two selected additives show positive effect on the stability of electrolytes under ex-situ stability tests and in situ flow cell experiments. The effects of additives on electrolyte are studied by Nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Raman spectroscopy, Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS) and charge-discharge test. The results show that a VFB using the electrolyte with NH(4)H(2)PO(4)additive demonstrates significantly improved redox reaction reversibility and activity, and higher energy efficiency. In addition, the cell employing the electrolyte with NH4H2PO4 exhibits a charge capacity fading rate much slower than the cell without additives during the cycling at high temperature. These results indicate that the phosphate additives are highly beneficial to improving the stability and reliability of VFB. (C) 2015 Elsevier Ltd. All rights reserved.

The investigation of the active centers in titanium zeolite was conducted by a probe reaction, the oxidation of trimethylphosphine. The different sites of TS-1 zeolite can be clearly distinguished through P-31 solid-state MAS NMR spectra of adsorbed trimethylphosphine. The results showed that only the trimethylphosphine bound to the coordinate-unsaturated framework Ti sites and the distorted tetrahedral Ti sites ofTS-1 zeolite could be easily oxidized by urea hydrogen peroxide. Diffuse Reflectance UV-Vis and Si-29 MAS NMR spectra further confirmed that the titanium peroxide species (TiOOH), which is formed through the solid-solid interaction between urea-H2O2 and TS-1 zeolite, could be catalytic active centers during the oxidation of trimethylphosphine. (C) 2015 Elsevier B.V. All rights reserved.

We investigate the influence of interlayer Neel coupling on the magnetization reversal processes in epitaxial Co(5 nm)/Cu(5 nm)/Co(5 nm) stripes by experimental methods and computer modeling. The stripes with a width of 900 and 1800 nm were formed on a step-bunched Si(111) substrate by molecular beam epitaxy and focused ion beam etching. Uniaxial magnetic anisotropy with the easy axis of the magnetization along the steps is induced in the stripes by the steps of the Si(111) substrate. The stepped structure of the layers in the multilayered stripes reproduces the morphology of the Si(111) substrate. Neel coupling between the Co layers is realized due to the unidirectional roughness at the Co/Cu interfaces caused by the steps of the substrate. Interlayer Neel coupling at the interfaces overcomes antiparallel magnetostatic interaction realized through the sides of the Co layers in the trilayered stripes. We used a modified Neel model in the simulation of the magnetization reversal in the multilayered system with unidirectional interface roughness. The surface energy of Neel coupling was spatially varied against the direction of the magnetization relative to the step edge. The results of micromagnetic simulations of the Co/Cu/Co stripes with spatially non-uniform and averaged surface energies of interlayer Neel coupling are compared and discussed.

In this paper, we demonstrate a novel thermal reflow method with an additional near ultraviolet (UV) flood exposure and upside-down reflow configuration for the fabrication of microlenses with an ultrahigh focal number. By using this method, microlenses with a focal number (F#) as high as 9.7 have been successfully obtained, which is about four fold higher than that can be fabricated with a conventional reflow method. The final profile of the microlenses can be flexibly and accurately tuned by controlling the flood exposure dosage and adopting the appropriate reflow configuration, which enables fabrication not only of spherical microlenses but also of more complex aspheric lenses. The fabricated microlens is characterized by measuring the point spread function (PSF) and the measurement result indicates that the diffraction limited optical performance of the microlens can be achieved. The method developed in this work can be used for the mass and cost-effective fabrication of high performance microlenses with ultrahigh focal numbers, which can find applications such as in accurate optical testing, integration imaging, and laser beam collimating.

Magnetic nanostructures with perpendicular magnetic anisotropy (PMA), as compared with the spin valves with in-plane anisotropy, have a lower level of thermal magnetization noise due to the high value of PMA, as well as a lower critical current density required for magnetization reversal nanostructures [1, 2].

The reflectometry diagnostics on experimental advanced superconducting tokamak (EAST) are composed of Q-band (32–56 GHz), V-band (48–76 GHz) and W-band (72–110 GHz) microwave reflectometers with X-mode polarization. The three reflectometers with separate frequency bands were launched independently in previous experiments and now are combined together by applying advanced microwave technology. A quasi-optical (QO) combiner/de-combiner by using frequency selective surfaces (FSSs) has been built to combine the three bands so that these waves (32–110 GHz) can be transmitted to the antenna by using one single oversized waveguide. Two double-ridged horns are used for launcher and receiver. The received waves are decoupled by using a QO de-combiner, the same with the combiner. The designed parameters and laboratory test results of the upgraded system have been presented. The density pedestal evolution during the edge localized modes (ELMs) in EAST plasma have been presented as an example for the application of the updated reflectometers.