Spectromicroscopy of Nanoscale Materials in the Tender X-Ray Regime Enabled by a High Efficient Multilayer-Based Grating Monochromator.

The combination of near edge X-ray absorption spectroscopy with nanoscale X-ray imaging is a powerful analytical tool for many applications in energy technologies, catalysis, which are critical to combat climate change, as well as microelectronics and life science. Materials from these scientific areas often contain key elements, such as Si, P, S, Y, Zr, Nb, and Mo as well as lanthanides, whose X-ray absorption edges lie in the so-called tender photon energy range 1.5-5.0 keV. Neither conventional grazing incidence grating nor crystal monochromators have high transmission in this energy range, thereby yielding the tender photon energy gap. To close this gap, a monochromator setup based on a multilayer coated blazed plane grating and plane mirror is devised. The measurements show that this novel concept improves the photon flux in the tender X-ray regime by two-orders-of-magnitude enabling previously unattainable laboratory and synchrotron-based studies. This setup is applied to perform nanoscale spectromicroscopy studies. The high photon flux provides sufficient sensitivity to obtain the electronic structure of Mo in platinum-free MoNi4 nanoparticles for electrochemical energy conversion. Additionally, it is shown that the chemical bonding of nano-structures in integrated circuits can be distinguished by the electronic configuration at the Si-K edge.

First Observation of New Flat Line Fano Profile via an X-Ray Planar Cavity.

A new Fano profile of a flat line is achieved experimentally by manipulating the relative amplitude of the continuum path, when q takes the pure imaginary number of -i in the x-ray regime. The underlying mechanism is that the interference term in the scattering will cancel the discrete term exactly. This new Fano profile renders only an observable continuum along with an invisible response to the discrete state of atomic resonance. The results suggest not only a different strategy to invisibility studies which provides a possible tool to identify weaker structures hidden by the strong white line, but also a new scenario to enrich the manipulations of two-path interference and nonlinear Fano resonance.

[Variation of O3 Concentration in Different Regions of Beijing from 2006-2015].

O3 continuous monitoring data for the Dingling, Guanyuan, Liulihe, and Qianmen sites from 2006-2015 were analyzed to investigate concentration levels, variation trends, temporal variations, and relationships with precursors and meteorological factors. The results showed that the ten year average concentrations of O3 at the Dingling site were the highest at 65.2 µg·m-3, followed by concentrations at Liulihe (53.4 µg·m-3), Guanyuan (49.6 µg·m-3) and Qianmen (40.4 µg·m-3). The O3 concentrations at Dingling showed a decreasing trend[0.5 µg·(m3·a)-1], while O3 concentrations at Guanyuan[0.9 µg·(m3·a)-1], Liulihe[0.3 µg·(m3·a)-1], and Qianmen[0.3 µg·(m3·a)-1] showed an increasing trend. The highest monthly average concentrations appeared during June and August, and the highest frequency occurred in July (17 times) with average concentrations of 99.8 µg·m-3. The lowest monthly average concentrations appeared during November and February, and the highest frequency occurred in January (14 times) with an average concentration of 16.6 µg·m-3. Notably, the time for the peak concentrations of O3 appeared earlier in the day in recent years. The peak concentrations of O3 appeared at 15:00-16:00 during 2013-2015, which was 1-2 hours earlier than previous years. The heavy air pollution of O3 occurred on 11 days at the Dingling site in 2015, which was ten days more than in 2013, indicating O3 pollution in the downwind suburban regions of Beijing in summer became more and more serious. The concentrations of O3 and NO2 at Dingling showed a positive correlation, while the concentrations of O3 and NO2 at the other sites showed a negative correlation, indicating O3 formation in Dingling was sensitive to NO2 chemistry, while O3 formation at the other sites was sensitive to VOC chemistry. The concentrations of O3 showed a positive correlation with temperature and negative correlations with humidity and surface pressure. Temperature had the greatest influence on O3 concentration, followed by surface pressure and humidity. For cases when daily maximum temperature exceeded 30℃ and relative humidity was between 30% and 70%, the probability of the O3 daily maximum 8 h concentration exceeding 200 µg·m-3 was high, indicating the air quality level reached levels for light pollution and moderate pollution.

[Exploring the Severe Haze in Beijing During December, 2015: Pollution Process and Emissions Variation].

Severe haze episodes shrouded Beijing and its surrounding regions again during December, 2015, causing major environmental and health problems. Beijing authorities had launched two red alerts for atmospheric heavy pollution in this period, adopted a series of emergency control measures to reduce the emissions from major pollution sources. To better understand the pollution process and emissions variation during these extreme pollution events, we performed a model-assisted analysis of the hourly observation data of PM2.5, and meteorological parameters combined with the emissions variation of pollution sources. The synthetic analysis indicated that: (1) Compared with the same period of last year, the emissions of atmospheric pollution sources decreased in December 2015. However, the emission levels of primary pollutants were still rather high, which were the main intrinsic causes for haze episodes, and the unfavorable diffusion conditions represented the important external factor. High source emissions and meteorological factors together led to this heavy air pollution process. (2) Emergency control measures taken by the red alert for heavy air pollution could decrease the pollutants emission by about 36% and the PM2.5 concentrations by 11% to 21%. Though the implementation of red alert could not reverse the evolution trend of heavier pollution, it indeed played an active role in mitigation of PM2.5 pollution aggravating. (3) Under the heavy pollution weather conditions, air pollutants continued to accumulate in the atmosphere, and the maximum effect by taking emergency measures occurred 48-72 hours after starting the implementation; therefore, the best time for executing emergency measures should be 36-48 hours before the rapid rise of PM2.5 concentration, which requires a more powerful demand on the accuracy of air quality forecast.

[Different Air Pollution Situations of O3 and PM2.5 During Summer in Beijing].

Two different pollution situations of O3 and PM2.5 during summer in Beijing were analyzed from theperspective of synoptic situations, meteorological elements, precursors, atmospheric oxidation, back-trajectories of air mass and chemical compositions of PM2.5. The results showed that the synoptic situations in the pollution situation that O3 reached middle level pollution and PM2.5 maintained low concentrations (O3high-PM2.5 low) could be characterized as northwest gas flow in 500 hPa height and high-pressure rear in the ground. Whereas the synoptic situations in the pollution situation that O3 and PM2.5 both reached middle level pollution (O3-PM2.5 high) could be characterized as westerly gas flow in 500 hPa height and low pressure in the ground. Compared with the O3high-PM2.5 low situation, meteorological elements in O3-PM2.5 high situation could be characterized as stronger southerly winds and higher relative humidity. In the O3-PM2.5 high situation, initial concentrations of O3 and PM2.5 were higher and diurnal variations of PM2.5 were more significant, nevertheless, the average concentrations of O3 were lower than those in the O3high-PM2.5 low situation, respectively. The analysis of precursors, atmospheric oxidation and chemical compositions of PM2.5 showed that the accumulation and hygroscopic growth of PM2.5 under unfavorable meteorological conditions as well as the regional transport caused by strong southerly winds might be the main factors leading to high PM2.5 concentrations in O3-PM2.5 high situation.

[Scavenging Effect of Rime and East Wind on PM2.5 Under Air Heavy Pollution in Beijing].

In order to study the scavenging effect of rime and east wind on the concentrations of PM2.5 in Beijing during the air heavy pollution, PM2.5 concentration data of some mountains and plains stations was used, together with meteorological data, wind profile data, aerosol extinction coefficient radar data collected during December 19 to 27, 2015, to analyze the clearance mechanisms of rime and east wind on PM2.5.The results showed that ①the removal of PM2.5 by rime was a different mechanism from that by the north wind and rainy weather, in the cooling conditions, the droplets touched the branches, wire for solid condensation, leading to formation of rime, and the concentration of PM2.5 decreased;②the east wind is a special kind of wind in Beijing area, when easterly wind decreased with height, a strong upward motion could be formed, and the PM2.5 was uplifted from the surface layer to the top, while with larger westerly wind in top, it was removed into downstream and cleaned; when east wind increased with height, a weak downward movement was easy to form, and when this sinking motion could not reach the ground, the surface layer of PM2.5 capacity became small, which was beneficial to increase the concentration of PM2.5;③the PM2.5scavenging ability of east wind depended on two points, one was the strength and development of upward movement of the height formed by the east wind, and the second was the initial height of uplifted motion formed by east wind, the lower the origin of the ascending motion height, the more obvious the removal of PM2.5;④after occurrence of east wind, along with the ascending motion to m·s-1 magnitude, the mixed layer height increased to 1200-1800 meters, and PM2.5 was uplifted to top layer and cleaned.

[Implementation results of emission standards of air pollutants for thermal power plants: a numerical simulation].

The emission inventory of air pollutants from the thermal power plants in the year of 2010 was set up. Based on the inventory, the air quality of the prediction scenarios by implementation of both 2003-version emission standard and the new emission standard were simulated using Models-3/CMAQ. The concentrations of NO2, SO2, and PM2.5, and the deposition of nitrogen and sulfur in the year of 2015 and 2020 were predicted to investigate the regional air quality improvement by the new emission standard. The results showed that the new emission standard could effectively improve the air quality in China. Compared with the implementation results of the 2003-version emission standard, by 2015 and 2020, the area with NO2 concentration higher than the emission standard would be reduced by 53.9% and 55.2%, the area with SO2 concentration higher than the emission standard would be reduced by 40.0%, the area with nitrogen deposition higher than 1.0 t x km(-2) would be reduced by 75.4% and 77.9%, and the area with sulfur deposition higher than 1.6 t x km(-2) would be reduced by 37.1% and 34.3%, respectively.

Correction method for the self-absorption effects in fluorescence extended X-ray absorption fine structure on multilayer samples.

A novel correction method for self-absorption effects is proposed for extended X-ray absorption fine structure (EXAFS) detected in the fluorescence mode on multilayer samples. The effects of refraction and multiple reflection at the interfaces are fully considered in this correction method. The correction is performed in k-space before any further data analysis, and it can be applied to single-layer or multilayer samples with flat surfaces and without thickness limit when the model parameters for the samples are known. The validity of this method is verified by the fluorescence EXAFS data collected for a Cr/C multilayer sample measured at different experimental geometries.

Significance and prognostic value of Gli-1 and Snail/E-cadherin expression in progressive gastric cancer.

Abnormal activation of the hedgehog (Hh) signaling pathway has been found to be involved in the occurrence, invasion, and metastasis of cancers. Epithelial-mesenchymal transition (EMT) also plays an important role in the invasion and metastasis of cancers. However, the significance of the Hh signaling pathway and EMT in the invasion and metastasis of gastric cancer is still unclear. This study aimed to investigate the significance and prognostic value of the Hh signaling pathway and EMT in progressive gastric cancer. Immunohistochemistry was performed to detect the expression of the Hh-induced transcriptional factor Gli-1 and the EMT-related molecules Snail and E-cadherin in 121 patients with progressive gastric cancer. Histological type, depth of invasion, lymph node metastasis, and pTNM stage were also recorded. In progressive gastric cancer, Gli-1 expression increased markedly, and was closely associated with increased Snail expression and decreased E-cadherin expression. Diffuse type cancer, lymph node metastasis, and abnormal expression of E-cadherin were independent factors influencing the prognosis of patients with progressive gastric cancer. These findings suggest that abnormal activation of the Hh signaling pathway is closely related to the presence of EMT and is an important factor influencing the prognosis of patients with diffuse progressive gastric cancer.

[Temporal and spatial distribution characteristics of ozone in Beijing].

Ozone concentrations obtained from 35 automatic air monitoring stations in Beijing were analyzed to investigate their temporal and spatial distribution characteristics. A process with high ozone concentration in summer was analyzed. The results showed that ozone maintained relatively high concentration from May to August while in other months, the ozone concentration was at a low level. Overall, the average concentrations of ozone in different stations in a descending order were comparison and regional station, suburban environment evaluation station, urban environmental assessment station and traffic pollution monitoring station. Ozone diurnal variation showed a single peak distribution, the peak of which appeared at 15:00 or 16:00. Ozone concentration showed obvious weekend effect, which meant ozone concentration in daytime of weekend was higher than that in weekday. Ozone concentration was lower in urban Beijing, higher in surrounding counties and the highest in northeast area with more vegetation. A high ozone concentration process occurred in Beijing on June 3, 2013. Under the effect of southwest wind in the afternoon, the concentration peaks of ozone in Yufa, Fengtaihuayuan, Olympic center and Huairou station occurred in order from south to north. Concentration peak of ozone in Huairou station occurred at 20:00 in the night. It could be concluded that significant ozone transmission characteristic was reflected in this process.

Submicrometer aluminum spheres' adhesion to planar silicon substrates.

We investigate the adhesion mechanism of aluminum spheres on a silicon substrate. Aluminum particles in the size range of 60-1500 nm were deposited onto a silicon substrate. It was found that aluminum particles underwent plastic deformation rather than elastic deformation because of van der Waals interactions. A finite element model developed recently is also used to analyze our results. Because the MP model was proposed to describe plastic deformation based on an analysis of metal microcontacts, our results prove the correctness of the MP model from its origin and basis of arguments.

Preparation of spherical silica particles by Stöber process with high concentration of tetra-ethyl-orthosilicate.

In this paper, Stöber process with high concentration of tetra-ethyl-orthosilicate (TEOS) up to 1.24 M is used to prepare monodisperse and uniform-size silica particles. The reactions are carried out at [TEOS]=0.22-1.24 M, low concentrations of ammonia ([NH(3)]=0.81[TEOS]), and [H(2)O]=6.25[TEOS] in isopropanol. The solids content in the resulting suspension achieves a maximum value of 7.45% at 1.24 M TEOS. Various-sized particles in the range of 30-1000 nm are synthesized. The influences of TEOS, NH(3), and H(2)O on the size and size distribution of the particles are discussed. A modified monomer addition model combined with aggregation model is proposed to analyze the formation mechanism of silica particles.

Contact between submicrometer silica spheres.

Recently, the scope of the investigation of the deformation mechanism extended to the micrometer and submicrometer regimes. The sphere-substrate contact method was usually used because it is rather difficult to make two micrometer or submicrometer spheres contact each other precisely. Here, we used the sphere-sphere contact method via a novel, simple process to investigate the deformation of spheres. The silica particle size ranges from 400 to 900 nm. Traditionally, the harder the particle, the smaller both the contact radius and the adhesion force. Therefore, it is widely accepted that silica particles should undergo elastic deformation, but we found that silica particles underwent plastic deformation rather than elastic deformation because of van der Waals interaction. The contact radii were observed by scanning electron microscopy (SEM).

Optical nonlinearity enhancement in heterostructures with thick metallic film and truncated photonic crystals.

It is hard to use bulk metals with high nonlinear susceptibilities since they are nearly opaque. Metal-dielectric photonic crystals can be transparent, but the electric field at each metal layer is still low. We theoretically studied the nonlinear response of heterostructures composed of truncated all-dielectric photonic crystals and thick metallic films. Because of the localized interface modes, both transmittance and the electric field in the metal are enhanced greatly. Compared to metal-dielectric photonic crystals, the critical intensity of threshold for bistability in the heterostructures with the same thickness of metal can be reduced by nearly 2 orders of magnitude.

Design of transmission multilayer polarizer for soft X-ray using a merit function.

A new method of designing soft X-ray transmission multilayer polarizer for use at a single wavelength using a merit function has been eveloped. A merit function of product of p-transmittance throughput and logarithm of transmittance polarization ratio was chosen. Characteristics of Mo/Si multilayer calculated using the merit function at 13.0 nm have been compared with those calculated using the traditional method by the present authors and those reported so far. The merit function has given the most optimal results of throughput of 30.0% and polarization ratio of 202. The polarizers of much higher polarization ratio or much larger p-transmittance can be designed by choosing the number of layers and optimizing the thickness of each layer to maximize the merit function. Using this method, the roughness effect has been studied on Mo/Si and La/B multilayer polarizers at 13.0 nm and 6.7 nm, respectively. It was found that the influence of roughness is crucial in shorter wavelength region.