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In order to solve such as difficulties in backfilling narrow foundation trenches in engineering, it was proposed to use alkali-activated slag cement (AASC) instead of traditional Portland cement to solidify silt and form AASC fluidized solidified soil. The effect of the content of AASC and the curing period on fluidized solidified soil has been studied by unconfined compression strength test, SEM and EDS. Moreover, the root cause for the improvement of the strength by the microstructure was explored. The results showed that: The fluidity increased first and then decreased with the increase of the content of AASC; 40% was the optimal content; in the same curing period, the unconfined compression strength increased with the increase of the content; 40% was the optimal content; the soil with different contents could reach the most of the 28d strength on Day 7; AASC generated a lot of low-Ca/Si C-S-H gel that consolidated soil particles into a denser structure. These results provide a theoretical basis for the application of AASC in fluidized solidified soil engineering.

In August 2022, Pakistan experienced an unprecedented precipitation event that caused significant damage. Analysis of the observations reveals that this extreme rainfall is primarily driven by anomalous atmospheric zonal advection, resulting in an anomalous water vapor concentration in Pakistan. The climatological meridional advection also contributes to this flooding. Anomalous easterly winds and low-level vertical convection combine to be critical factors contributing to the moisture concentration over the country. Further investigation identifies the air-sea interaction over the tropical Indian Ocean and abnormal warming over the Arabian Sea are crucial factors influencing this extreme flooding event. The concurrent occurrence of a negative Indian Ocean Dipole event and the warming sea surface temperature anomalies in the northern Arabian Sea intensifies the easterly winds over Pakistan, helping to transfer the anomalous water vapor from the remote region into Pakistan, ultimately contributing to the extreme flooding in 2022.

The multidecadal changes of dust column mass density (DCMD) in Gobi desert (GD) in spring are investigated based on the Modern-Era Retrospective analysis for Research and Applications version 2 dataset. In addition, the possible effects of the atmospheric circulation and sea surface temperature (SST) forcing on the multidecadal changes are analyzed. Results show that the dust aerosol over GD experienced a decadal change in 1999 with about 30% higher dust loading during 2000–2013 in comparison to that during 1987–1999. Further analysis indicates that the decadal change of dust aerosol over GD is attributed to the more strengthened northwesterly wind anomaly extending from lower to middle troposphere and the anticyclonic anomaly in middle troposphere over GD during the latter epoch, which is favorable to the increase of local dust activities. Furthermore, the decadal change of DCMD in GD is associated with the switch of Pacific Decadal Oscillation (PDO) phase. From 2000 to 2013, the PDO was in the negative phase, which induced to a positive potential height anomaly and northwesterly wind anomalies in the middle troposphere over GD. The dry and cold air brought by the anomalous northwesterly wind associated with the negative PDO phase reduces the relative humidity in the lower troposphere further amplify the effect of strengthened wind speed, being favorable for the increase of local dust loading and the resultant increase of DCMD there.

Investigation of aerosol effects on fog with long-term measurements has generally focused on fog occurrence frequency and intensity; here we examine the effects on fog lifetime, fog formation, and fog dissipation. From analysis of 52 years (1960–2011) of data collected at 404 stations in China, it is found that fog lifetime exhibits a clear increasing trend with time, and the increased lifetime is mainly attributable to delayed fog dissipation. Increased aerosol levels and global warming affect fog lifetime in opposite ways; increased aerosol levels serve to prolong fog lifetime by primarily delaying fog dissipation, whereas warming decreases fog lifetime by primarily delaying fog formation. The overall aerosol effect on fog lifetime in China is shown to predominate, especially in the highly polluted region of Eastern China. The observational findings are confirmed by a suite of WRF-Chem simulations that reveal the influences of both increased aerosol levels and temperatures through a complex chain of interactions among microphysical, dynamical, thermodynamic, and radiative processes.

Large-scale in situ observations are sorely lacking, leading to poor understanding of nationwide atmospheric turbulence over China. Nevertheless, high-resolution soundings have become available starting in 2011, providing a unique opportunity to investigate turbulence across China. Here, we calculated the mean turbulence dissipation rate ( ϵ ) from radiosonde measurements across China for the period 2011–2018 using Thorpe analysis. The atmospheric layers that had stronger turbulence indicated by larger ϵ generally came with larger Thorpe length but with smaller Brunt–Väisälä frequency. Overall, the clear-air ϵ in the free atmosphere exhibited large spatial variability with a ‘south-high north-low’ pattern. Large clear-air ϵ values were observed in both the lower stratosphere (LS) and upper troposphere (UT), especially over the Tibetan Plateau (TP) and its neighboring regions with complex terrain likely due to large-amplitude mountain waves. Particularly, less frequent but more intense clear-air turbulence was observed in both lower troposphere (LT) and UT over the TP, while more frequent, less intense clear-air turbulence was found in northern China. The all-sky turbulence considering the moist-saturation effects was much stronger in the troposphere, notably in southern China where convective clouds and precipitation oftentimes dominated. In the vertical direction, the altitude of peak clear-air ϵ in the troposphere was found to decrease poleward, broadly consistent with the meridional gradient of tropopause height in the Northern Hemisphere. A double-peak mode stood out for the profiles of clear-air ϵ at midlatitudes to the north of 30° N in winter: one peak was at altitudes of 15–18 km, and another at altitudes of 5–8 km. The strong shear instabilities around the westerly jet stream could account for the vertical bimodal structures. The seasonality of ϵ was also pronounced, reaching maxima in summer and minima in winter. Our results may help understand and avoid clear-air turbulence, as related to aviation safety among other issues.

Active layer thickness (ALT) is a critical metric for monitoring permafrost. How soil moisture influences ALT depends on two competing hypotheses: (a) increased soil moisture increases the latent heat of fusion for thaw, resulting in shallower active layers, and (b) increased soil moisture increases soil thermal conductivity, resulting in deeper active layers. To investigate their relative influence on thaw depth, we analyzed the Field Measurements of Soil Moisture and Active Layer Thickness (SMALT) in Alaska and Canada dataset, consisting of thousands of measurements of thaw depth and soil moisture collected at dozens of sites across Alaska and Canada as part of NASA’s Arctic Boreal Vulnerability Experiment (ABoVE). As bulk volumetric water content (VWC) integrated over the entire active layer increases, ALT decreases, supporting the latent heat hypothesis. However, as VWC in the top 12 cm of soil increases, ALT increases, supporting the thermal conductivity hypothesis. Regional temperature variations determine the baseline thaw depth while precipitation may influence the sensitivity of ALT to changes in VWC. Soil latent heat dominates over thermal conductivity in determining ALT, and the effect of bulk VWC on ALT appears consistent across sites.

Two nickel-based single-crystal (SC) superalloys (designated T6 and T13) were investigated in order to reveal the effects of stacking fault (SF) energy and diffusion on their high-temperature creep behavior. In this study, the effect of dislocation spacing on creep was the same between T6 and T13. The microstructure and deformation rate attained prior to 1% creep were investigated in detail. Several differences were detected in the two superalloys, the reasons for these differences were discussed. The results suggested that the SF energy of the γ matrix was the key factor affecting development of the dislocation network. Because the matrix of the T6 superalloy has lower SF energy than T13, the cross-slipping of dislocation was more difficult in the early stages of creep, which resulted in lower levels of dislocation propagation and of formation of the dislocation network. When creep had entered the steady stage, the key process controlling high-temperature creep was atomic migration in the γ matrix, and the creep rupture life was lengthened by reducing the penetration of dislocations into the γ ′ raft and slowing down its topological inversion.

To compare the effects of different surface treatment methods on the surface characteristics of yttria-stabilized tetragonal zirconia (Y-TZP) and relevant shear bond strength (SBS) between zirconia and composite resin. Forty-eight Y-TZP ceramics were randomly divided into four groups based on the specific surface treatments: Group C (blank treatment), Group Sand (sandblasting with 80 μ m Al _2 O _3 particles), Group HF (etched with 40% hydrofluoric acid for 10 min), and Group H _2 SO _4 (etched with hot sulfuric acid for 10 min). Surface characteristics of the treated specimens, including morphology, roughness, wettability, chemical composition and crystalline structure were analyzed. SBS was tested by bonding ceramics to resin cement in the same group. Kruskal-Wallis test followed by pair wise comparison was conducted for statistical processing. A significance level of α = 0.05 was set. Three kinds of surface structures with different widths and heights in roughness were obtained, including micron-scale pit/peak size by sandblasting, nano-scale pit/peak size by hydrofluoric acid etching and middle submicron-scale pit/peak size by hot sulfuric acid etching. By comparison, the specimens of Group HF showed the most favorable wettability, the highest SBS and the lowest phase transformation than those of other groups. Therefore, HF etching was considered as a promising surface treatment to promote resin–zirconia bonding without excessive surface damage. The height, width, frequency and regularity of roughness altogether affected the shear strength.

The Yukon–Kuskokwim (YK) Delta is a region of discontinuous permafrost in the subarctic of southwestern Alaska. Many wildfires have occurred in the YK Delta between 1971–2015, impacting vegetation cover, surface soil moisture, and the active layer. Herein, we demonstrate that the remotely sensed active layer thickness (ReSALT) algorithm can resolve the post-fire active layer dynamics of tundra permafrost. We generated a stack of Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar interferograms over a study region in the YK Delta spanning 2007–2010. We applied ReSALT to this stack of interferograms to measure seasonal subsidence associated with the freezing and thawing of the active layer and subsidence trends associated with wildfire. We isolated two wildfire-induced subsidence signatures, associated with the active layer and the permafrost layer. We demonstrate that InSAR is sensitive to increases in active layer thickness following wildfire, which recovers to pre-fire values after approximately 25 years. Simultaneously, we show that fire gradually thins the permafrost layer by 4 m, which recovers to pre-fire thickness after 70 years.

The Corn Belt of the United States, one of the most agriculturally productive regions in the world, experienced a globally anomalous decrease in annual temperatures and a concurrent increase in precipitation during the mid- to late-20th century. Here, we quantify the impact of this ‘warming hole’ on maize yields by developing alternative, no warming hole, climate scenarios that are used to drive both statistical and process-based crop models. We show that the warming hole increased maize yields by 5%–10% per year, with lower temperatures responsible for 62% of the simulated yield increase and greater precipitation responsible for the rest. The observed cooling and wetting associated with the warming hole produced increased yields through two complementary mechanisms: slower crop development which resulted in prolonged time to maturity, and lower drought stress. Our results underscore the relative lack of climate change impacts on central US maize production to date, and the potential compounded challenge that a collapse of the warming hole and climate change would create for farmers across the Corn Belt.

In this study, we reported a facile and rapid synthesis of NiAl LDH/ERGO and reduced by electrochemical method. Compared with previous studies, this experiment greatly decreased the use of reductive solvents and was environmentally friendly. The nanocomposite material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) & transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FT-IR). A series of electrochemical methods were applied to test the electrochemical performance of modified electrodes. When the modified electrode was used to detect AA, DA and UA, the three substances can be clearly separated and the limits of detection for AA, DA and UA can be 0.85 μM in the range 12.48-232 μM, 0.38 μM in the range 1.06-13.26 μM and 0.42 μM in the range 1.25-23.20 μM (S/N = 3), respectively. The modified electrode could provide a reproducible and stable platform to detect AA, DA, and UA simultaneously. [ABSTRACT FROM AUTHOR]

A sandwich-structured C3F7-azo+-TaWO6 nanocomposite used as an electrochemical sensor for simultaneous determination of dopamine (DA) and ascorbic acid (AA) was synthesized by guest-guest exchange method. n-PrNH3 +-TaWO6 precursor was ionexchanged with cationic polyfluorinated azo dye, trans-[2-(2,2,3,3,4,4,4-heptafluorobutylamino)ethyl]-{2-[4-(4-hexyphenylazo)- phenoxy]ethyl} dimethylammonium bromide (abbreviated as C3F7-azo+Br−). The structure and morphology were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer analysis (EDS) and Fourier transform infrared spectrometer (FTIR). Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used to test the electrochemical properties of C3F7-azo+-TaWO6 nanocomposite. The experimental results show that C3F7-azo+-TaWO6/GCE can detect AA and DA at the same time, with the potential difference reaching 356 mV. Moreover, electrochemical sensing toward DA and AA on C3F7-azo+-TaWO6/ GCE exhibits low detection limits of 0.81 μM and 1.6 μM, respectively, each in a linear range of 0.05 to 0.31 mM. [ABSTRACT FROM AUTHOR]

This work proposed a strategy for impedimetric detection of microRNAs (miRNAs) by the signal amplification of insulating biomaterials. Specifically, biotinylated miRNA (biotin-miRNA) with the same sequence as that of target miRNA was captured by the sensor electrode. The biotin tags on electrode surface allowed for the attachment of tetrameric streptavidin (SA) protein through the biotin-SA interaction. Meanwhile, biotinylated phenylalanine nanoparticles (biotin-FNPs) in solution triggered the assembly of more SA molecules on electrode surface through the same interaction. The circular recruitment of SA and biotin-FNPs from solution led to the in situ formation of SA-biotin-FNPs networks on electrode surface. The networks created an insulating layer to hamper the electron transfer, thus amplifying the impedance response. The competitive hybridization between target miRNA and biotin-miRNA with the capture probe prevented the attachment of biotin-miRNA by the sensor electrode, thus preventing the in situ formation of SA-biotin-FNPs networks and leading to the decrease in impedance signal. The method was applied to determine miRNA-21 in cell lysates with satisfactory results. The signal amplification strategy by in situ formation of nanoparticle networks can potentially be applied to develop novel affinity biosensors for detection of various biomolecules [ABSTRACT FROM AUTHOR]

In this work, a flexible three-dimensional nanoporous bimetallic Cu-Ag (NPCuAg) has been fabricated by a simple electrochemically dealloying Zr45Cu35Ag20 glassy ribbon in HF aqueous solution. The influence of dealloying treatment time on the thickness of nanoporous layer and the flexibility of the dealloyed ribbon was investigated. It is found that the thickness of NPCuAg is approximately proportional to dealloying treatment time, and the NPCuAg shows a maximum nanoporous layer ***9 μm (one side) while possessing good flexibility. Furthermore, nanoporous CuOAg (NPCuOAg) was obtained through a simple oxidation treatment. The NPCuOAg shows a hierarchical structure where CuO nanosheets are uniformly embedded in 3D nanoporous Ag skeleton. The NPCuOAg battery-type electrode exhibits superior electrochemical performance, which has great potential application in flexible high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Aseries of mesoporous TiO2 (MT) materials were synthesized by a hydrothermal procedure using Cetyltrimethyl ammonium bromide (CTAB) and Poly (ethylene-glycol)-block-poly (propylene-glycol)-block-poly(ethylene-glycol) (P123) as templates, and titanium tetrachloride as a titanium source. The molar ratios of Ti/CTAB and Ti/P123 were optimized via Brunauer-Emmett-Teller (BET) measurement. MT materials made with the two templates formed rutile and anatase crystal phases as indicated by X-ray diffraction (XRD) and laser Raman spectrometry (LRS). Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) characterization indicate that the anatase MT material formed by P123 template shows immense potential as photoanode in dye sensitized solar cell (DSSC) devices. The analysis of current to voltage (J-V) curves and electrochemical impedance spectroscopy (EIS) corroborated the previous characterizations and the highest power conversion efficiency (PCE) of the cells involvingMT using P123 with a Ti/P123 molar ratio of 13:1 as the templates reached 8.12%, which is much higher than that with CTAB (5.43%) as a template and commercial P25 (5.15%) based devices. [ABSTRACT FROM AUTHOR]

LiNi0.5Mn1.5O4 (LNMO) is one of the high potential cathodes for lithium-ion batteries due to high operating voltage (4.7 V vs. Li) and high specific energy (650 Wh· kg-1). However, severe accelerated performance degradation occurring especially at the interface between electrode and electrolyte, hinder the implementation of the LNMO. In this work, porosity-graded cathodes are designed to mitigate LNMO degradation. The LNMO is synthesized using the solid-state reaction. We confirm the crystalline phase and electrochemical performance of the synthesized LNMO via X-ray powder diffraction (XRD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Scanning electron microscope (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) are utilized. The porosities are measured by both 2-D imaging method (i.e., through ImageJ) and 3-D pore size analyzer in this study. Cycling tests show that porosity-graded cells reduce the capacity fade about 8.285% in full cell and 5.29% in half-cell, respectively. The porosity increase can improve the conductivity and diffusivity of lithium-ions through the electrode. Also, solid electrolyte interphase (SEI) formation can be varied and controlled when the porosity is different inside the electrode. Furthermore, we adopted Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II) to demonstrate the porosity-grading as a strategy for mitigating battery degradation. [ABSTRACT FROM AUTHOR]

Battery design variable optimization can significantly affect battery capacity, discharge specific power, and discharge specific energy. However, many design variables need to be taken into consideration, which requires intensive computation and simulation. Our previously developed comprehensive battery degradation model is utilized in this optimization study via parallel computing. A three-electrode cell is developed for model validation over long term cycling. The objectives of optimization are maximizing discharge specific power and specific energy as well as minimizing capacity loss. Several design variables (e.g., thickness, particle size, and porosity) are optimized through a modified Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II). The obtained Pareto-optimal solutions that show electrode thickness, particle sizes, porosity, and conductivity are the battery design variables that can significantly affect battery performance. In addition, a sensitivity analysis suggests that a thicker electrode and a smaller particle size can improve battery performance. The optimized batteries have a better performance over 750 cycle's simulation: less SOC swing and less reduction of capacity. The design optimization framework developed herein can be modified and applied to various type of batteries with different optimization objectives and battery design variables. [ABSTRACT FROM AUTHOR]

In this study, a phase-field model is developed to simulate the microstructure morphology evolution that occurs during solid electrolyte interphase (SEI) growth. Compared with other simulation methodologies, the phase-field method has been widely applied in the solidification modeling that has great relevance to SEI formation. The developed model can simulate SEI structure and morphology evolution, and can predict SEI thickness growth rate. X-ray photoelectron spectroscopy (XPS) experiments are performed to confirm the major SEI species as LiF, Li2O, ROLi, and ROCO2Li. Transmission electron microscopy (TEM) experiment is performed to present the SEI layer structures. The experiments reduce the complexity of the model development and provide validation to some extent. Fick's law and mass balance are applied to investigate lithium-ion concentration distributions and diffusion coefficients in different types of SEI layers predicted by the phase-field simulations. Simulation results show that lithium-ion diffusion coefficients between 298 K and 318 K are 1.340-7.328(10-16) cm²/s, 1.734-3.405(10-12) cm²/s, and 2.611-2.389(10-15) cm²/s in the compact, porous, and multilayered structures of SEI layer, respectively. The resistances between 298 K and 318 K are 0.740-1.693 Ω⋅cm², 2.827-5.517 Ω⋅cm², and 3.726-5.839 Ω⋅cm² in the compact, porous, and multilayered structures of SEI layer, respectively. [ABSTRACT FROM AUTHOR]

How to evaluate plasma-derived heat (PDH) and the synergistic effect of plasma catalysis, especially for in-plasma catalysis (IPC), is still ambiguous. In this work, to exclude the reaction-heat impact on PDH, N2 plasma was first used to compare the heat-uninsulated and heat-insulated cases for empty and packed dielectric barrier discharge (DBD). Compared with the heat-uninsulated cases, the heat-insulation has nearly the same discharge characteristics, and a weak impact on N2 rotational temperature. The heat-insulation, whether for empty or packed DBD, gave much higher outgoing gas temperature (Tg) and reactor wall temperature (Tw) than the heat uninsulation. For methanol-steam reforming in the heat-insulated reactor over various supported catalysts on Al2O3 support (AS), the dependence of PDH indicated by Tw on reaction-heat power was observed. The synergistic effect of plasma and Au/CeZn/AS catalyst in the heat-insulated IPC reactor was verified. For the plasma alone case, methanol conversion was negligible, giving a Tw of 618 K. For the IPC case, the Tw decreased considerably to 545 K due to the effect of reaction-heat power on PDH. Methanol conversion of 46.8% was achieved, which is much higher than the catalysis alone case of 9.0%, even at a higher temperature of 573 K. Moreover, H2 selectivity increased from plasma alone from 80.0% to 95.1%. If the IPC case was heat-uninsulated, the Tw dropped down to 385 K, and accordingly methanol conversion became insignificant. This work demonstrated that heat-insulation is necessary for reliable evaluation of the PDH and the synergistic effect in plasma catalysis. [ABSTRACT FROM AUTHOR]

A two-dimensional binary driven disk system embedded by impermeable tilted plates is investigated through nonequilibrium computer simulations. It is well known that a binary disk system in which two particle species are driven in opposite directions exhibits jammed, phase separated, disordered, and laning states. The presence of tilted plates can not only advance the formation of laning phase, but also effectively stabilize laning phase by suppressing massively drifting behavior perpendicular to the driving force. The lane width distribution can be controlled easily by the interplate distance. The collective behavior of driven particles in laning phase is guided by the funnel-shaped confinements constituted by the neighboring tilted plates. Our results provide the important clues for investigating the mechanism of laning formation in driven system. [ABSTRACT FROM AUTHOR]

As an intermedia between cold and thermal plasmas, warm plasma generated by gliding arc (GA) discharge possesses high conversions and high energy efficiencies for CO2 conversion. However, there is little understanding for the arc characteristics in CO2-based atmosphere and reaction mechanism of CO2 in GA plasma from experimental approach. For this purpose, a magnetically driven GA plasma with a constant length of arc is designed to study GA characteristics and reaction mechanism by changing H2/CO2 molar ratio (from pure CO2 to pure H2). In the entire range of H2/CO2 ratio, the arc channel shows a glow-like feature. The plasma parameters are arc temperature of 2200–3600 K, electron density of ~1.6  ×  1014 cm−3 and electron temperature of ~3 eV. From pure CO2 to pure H2, arc diameter decreases from 1.3 to 0.6 mm, whereas rotational frequency increases from 20 to 64 Hz. Based upon the optical emission spectra of CO, OH, H and O species, chemluminescence spectra of CO and O recombination and CO production rate detected online by gas chromatographs, the reaction mechanism at low and high H2/CO2 molar ratios is disclosed. [ABSTRACT FROM AUTHOR]

GaN-based yellow light-emitting diodes (LEDs) on Si substrates are aged at a direct current density of 50 A/cm2 for 500 h. After the aging process, it can be found that the LEDs have a stable electrical property but their light output power is decayed by 4.01% at 35 A/cm2. Additionally, the aging mechanism of GaN-based yellow LED is analyzed. It is found that the decay of light output power may be attributed to the following two reasons: one is the increase of Shockley–Rrad–Hall recombination and the other is the change of the transport path of holes via V-pits after aging, which may induce the radiative recombination current to decrease. In this paper, not only the aging mechanism of GaN-based yellow LED is investigated, but also a new possible research direction in LED aging is given. [ABSTRACT FROM AUTHOR]

Phonon sidebands in the electrolumiescence (EL) spectra of InGaN/GaN multiple quantum well blue light emitting diodes are investigated. S-shaped injection current dependence of the energy spacing (ES) between the zero-phonon and first-order phonon-assisted luminescence lines is observed in a temperature range of 100–150 K. The S-shape is suppressed with increasing temperature from 100 to 150 K, and vanishes at temperature above 200 K. The S-shaped injection dependence of ES at low temperatures could be explained by the three stages of carrier dynamics related to localization states: (i) carrier relaxation from shallow into deep localization states, (ii) band filling of shallow and deep localization states, and (iii) carrier overflow from deep to shallow localization states and to higher energy states. The three stages show strong temperature dependence. It is proposed that the fast change of the carrier lifetime with temperature is responsible for the suppression of S-shaped feature. The proposed mechanisms reveal carrier recombination dynamics in the EL of InGaN/GaN MQWs at various injection current densities and temperatures. [ABSTRACT FROM AUTHOR]

While classic reforming processes rely on heat and chemical equilibrium, plasma-based reforming processes possess the ability to induce non-equilibrium and reactive chemistry at low temperatures using high energy electrons. To better understand the distinctive roles of both electron-induced chemistry and thermochemistry during plasma-assisted fuel reforming, we previously developed a temperature-controlled dielectric barrier discharge (DBD) reactor, which controlled the gas temperature and the electron temperature independently. Here, we investigate plasma-assisted steam reforming of methane using the temperature-controlled DBD reactor and electron-kinetics calculations. We investigated the individual effects of the determining factors for electron-induced chemistry (i.e. reduced electric field intensity and discharge power) and for thermochemistry (i.e. background gas temperature) by varying the discharge power, gas temperature, and pressure inside the reactor. As a result, we found that both the electron-induced chemistry and thermochemistry governed the reactant conversions. Thermochemistry positively affected the methane conversion in particular, but negatively affected the water conversion as the gas temperature increased. The electron-induced chemistry weakly affected the product distribution, while the background temperature (thermochemistry) strongly influenced the product selectivity and composition by altering the chemical pathways involving the plasma-generated reactive species at the given temperature. [ABSTRACT FROM AUTHOR]

Effect of hydrogen (H2) treatment during the GaN barrier growth on the electroluminescence performance of green InGaN/GaN single-quantum-well light-emitting diodes (LEDs) grown on Si substrates is experimentally investigated. We prepare two LED samples with different carrier gas compositions during the growth of GaN barrier. In the H2free LED, the GaN barrier is grown in full nitrogen (N2) atmosphere. For the other H2treated LED, a mixture of N2and H2was used as the carrier gas. It is observed that V-shaped pits decrease in size after H2treatment by means of the scanning electron microscope. Due to the fact that the p–n junction interface would be closer to the p-GaN as a result of smaller V-shaped pits, the tunneling barrier for holes to inject into the InGaN quantum well would become thicker after H2treatment. Hence, the external quantum efficiency of the H2treated LED is lower compared to the H2free LED. However, LEDs would exhibit a better leakage behavior after H2treatment during the GaN barrier growth because of more effective blocking of the threading dislocations as a result of the H2etching at V-shaped pits. [ABSTRACT FROM AUTHOR]

InGaN-based green light-emitting diodes (LEDs) with different green quantum well numbers grown on Si (111) substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7. [ABSTRACT FROM AUTHOR]

A blue emission originated from InGaN/GaN superlattice (SL) interlayer is observed in the yellow LEDs with V-pits embedded in the quantum wells (QWs), revealing that sufficient holes have penetrated through the QWs into SLs far away from the p-type layer. In the V-pits embedded LEDs, hole transport has two paths: via the flat c-plane region or via the sidewalls of V-pits. It is proved that the holes in SLs are injected from the sidewalls of V-pits, and the transportation process is significantly affected by working temperature, current density, and the size of V-pits. Four motion possibilities are discussed when the holes flow via the sidewalls. All these may contribute to a better understanding of hole transport and device design. [ABSTRACT FROM AUTHOR]

The solubility and bubble formation of hydrogen (H) in tungsten (W) are crucial factors for the application of W as a plasma-facing component under a fusion environment, but the data and mechanism are presently scattered, indicating some important factors might be neglected. High-energy neutron-irradiated W inevitably causes a local strain, which may change the solubility of H in W. Here, we performed first-principles calculations to predict the H solution behaviors under isotropic strain combined with temperature effect in W and found that the H solubility in interstitial lattice can be promoted/impeded by isotropic tensile/compressive strain over the temperature range 300–1800 K. The calculated H solubility presents good agreement with the experiment. Together, our previous results of anisotropic strain, except for isotropic compression, both isotropic tension and anisotropic tension/compression enhance H solution so as to reveal an important physical implication for H accumulation and bubble formation in W: strain can enhance H solubility, resulting in the preliminary nucleation of H bubble that further causes the local strain of W lattice around H bubble, which in turn improves the H solubility at the strained region that promotes continuous growth of the H bubble via a chain-reaction effect in W. This result can also interpret the H bubble formation even if no radiation damage is produced in W exposed to low-energy H plasma. [ABSTRACT FROM AUTHOR]

The form of the external potential (FEP) for generating field emission resonance (FER) in a scanning tunneling microscopy (STM) junction is usually assumed to be triangular. We demonstrate that this assumption can be examined using a plot that can characterize FEP. The plot is FER energies versus the corresponding distances between the tip and sample. Through this energy–distance relationship, we discover that the FEP is nearly triangular for a blunt STM tip. However, the assumption of a triangular potential form is invalid for a sharp tip. The disparity becomes more severe as the tip is sharper. We demonstrate that the energy–distance plot can be exploited to determine the barrier width in field emission and estimate the effective sharpness of an STM tip. Because FERs were observed on Pb islands grown on the Cu(111) surface in this study, determination of the tip sharpness enabled the derivation of the subtle expansion deformation of Pb islands due to electrostatic force in the STM junction. [ABSTRACT FROM AUTHOR]

We present a new method for achieving chemical reactions induced by plasmas with liquids—an in-liquid arc plasma jet system—designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility of the system was investigated in a wastewater treatment case with phenol as the model contaminant. We found that the specific energy input is a reasonable parameter by which to characterize the overall process. The phenol removal reaction could be modeled as a pseudo-first-order reaction, and the reaction constant became smaller as the phenol concentration increased. However, complete decomposition of the phenol into water and carbon dioxide required very high energy because the final intermediate, oxalic acid, is relatively stable. Detailed chemical and physical analyses, including byproducts, ions, solution acidity, and conductivity, were conducted to evaluate this new method for use in the appropriate applications. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are single stranded endogenous molecules composed of only 18–24 nucleotides which are critical for gene expression regulating the translation of messenger RNAs. Conventional methods based on enzyme-assisted nucleic acid amplification techniques have many problems, such as easy contamination, high cost, susceptibility to false amplification, and tendency to have sequence mismatches. Here we report a rapid, ratiometric, enzyme-free, sensitive, and highly selective single-step miRNA detection using three-way junction assembled (or self-assembled) FRET probes. The developed strategy can be operated within the linear range from subnanomolar to hundred nanomolar concentrations of miRNAs. In comparison with the traditional approaches, our method showed high sensitivity for the miRNA detection and extreme selectivity for the efficient discrimination of single-base mismatches. The results reveal that the strategy paved a new avenue for the design of novel highly specific probes applicable in diagnostics and potentially in microscopic imaging of miRNAs in real biological environments. [ABSTRACT FROM AUTHOR]

InGaN-based green light-emitting diodes (LEDs) with and without Mg-preflow before the growth of p-AlGaN electron blocking layer (EBL) are investigated experimentally. A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment, effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures. However, unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature. Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions. Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to p- GaN side through the c-plane rather than the V-shape pits, which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN. Within this framework, apparently disparate experimental observations regarding electroluminescence properties, in this work, are well reconciled. [ABSTRACT FROM AUTHOR]