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Significance Pluripotent stem cells are critical in both animal and plant development. Unlike higher animals, plants have unique postembryonic development, which continuously produce organs depending on shoot and root meristems. In the shoot meristem, division of the stem cells in the outermost layers provides the cells for all shoot structures. How those meristem cells are tightly controlled attracted intense studies. Genetic and molecular analyses in Arabidopsis have identified the key transcription factors WUSCHEL (WUS) and SHOOTMERISTEMLESS (STM) as the major regulators of pluripotency in the shoot meristem. Here, the results provide solid evidence showing how those two pluripotency factors WUS and STM coordinate to control shoot meristem cells strictly in plants., In the shoot meristem, both WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM), two transcription factors with overlapping spatiotemporal expression patterns, are essential for maintaining stem cells in an undifferentiated state. Despite their importance, it remains unclear how these two pathways are integrated to coordinate stem cell development. Here, we show that the WUS and STM pathways in Arabidopsis thaliana converge through direct interaction between the WUS and STM proteins. STM binds to the promoter of CLAVATA3 (CLV3) and enhances the binding of WUS to the same promoter through the WUS–STM interaction. Both the heterodimerization and simultaneous binding of WUS and STM at two sites on the CLV3 promoter are required to regulate CLV3 expression, which in turn maintains a constant number of stem cells. Furthermore, the expression of STM depends on WUS, and this WUS-activated STM expression enhances the WUS-mediated stem cell activity. Our data provide a framework for understanding how spatial expression patterns within the shoot meristem are translated into regulatory units of stem cell homeostasis.

The Electrical Submersible Pump (ESP) systems were deployed in two gas wells for the dewatering of the gas reservoir. However, problems, such as the failure to start up the ESP, and changes in reservoir parameters occurred during the production. For the first problem, the well start-up operation records indicate that the ESP’s gas locking happened. To avoid this, an optimization method of the well start-up procedure for the ESP well with a check valve was correspondingly proposed, which can solve the problem without any workovers. Secondly, based on the working characteristics of the ESP and the nodal analysis method, a set of optimization methods for the operating parameters of ESPs were introduced to achieve the inflow and outflow balance. For one well, the original ESP system was planned to be installed after hydraulic fracturing. Traditionally, the ESP operating parameters were designed based on the production rate. However, in this case, the production rate and the ESP operating frequency were designed simultaneously to maximize the pump efficiency.

As one of the significant part of IGFC (integrated gasification fuel cell) system, coal gasification technology has an important effect on system efficiency as well as technological process. To figure out what kind of gasifier technology could benefit IGFC system most, we select two representative gasifiers for comparison, which are E-Gas gasifier and Shell gasifier. In this study MW-level E-gas IGFC system and Shell IGFC system models are developed respectively, moreover, the energy analysis of two systems are carried out simultaneously. The results show that SOFC DC Power efficiency and system net plant efficiency of E-gas IGFC system are 52.82% and 50.89% , both higher than Shell IGFC system, which are 49.24% and 49.74%; under the same design conditions, gasifier with high content of CH 4 would be easier to obtain higher SOFC power efficiency as well as system net efficiency. The present work is helpful to provide gasifier selection suggestions for large-scale IGFC system.

Wheat harvest and subsequent straw burning for maize planting can cause severe PM2.5 and PAH pollutions and deteriorate the air quality of nearby cities in consequence. PM2.5 samples were collected in Baoding urban area (BUA) from June 18 to July 7 of 2019, during and after wheat harvest (DWH and AWH, respectively). The “Migration Effect” (i.e., PM2.5 and PAHs transferred from rural to urban during DWH and AWH, respectively) was proved by both the later time for appearance of peak values of PM2.5 and PAHs and the air mass origins in BUA. The daily average PM2.5 (reported in µg m–3) 137 of DWH was 2.58 times 53.1 of AWH for BUA, regardless of its lower levels than the corresponding 156 and 75.6 for an adjacent rural site (ARS). The reverse trend was found for PAH mass contents (in µg g–1), AWH possessed much higher value of 139 than 27.8 of DWH, while no significant fluctuations occurred for PAH concentrations due to the varied PM2.5 levels. Four PAH sources including biomass burning (BB), coal combustion (CC), vehicle exhaust (VE) and industrial emissions (IN) were identified using positive matrix factorization (PMF). BB was the biggest contributor during whole sampling period (WSP), followed by CC, VE, and IN. BB increased from 17.3% to 37.1% along with the transition from DWH to AWH, indicated the impact of straw burning for maize planting. High share of CC suggested that coal was still an important civil fuel. The strict emission reduction measures made the industry smallest contributor in BUA. Lower VE share in BUA than ARS demonstrated that influence of high-intensity operation of wheat harvesters and rotary cultivators.

Wheat harvesting significantly alters the characteristics of PM2.5 in both rural regions and the adjacent urban areas. We conducted a systematic PM2.5 sampling campaign at two sites, one rural (ARS) and the other urban (UA), in the center of the Beijing-Tianjin-Hebei megalopolis during and after the wheat harvest (WH). The PM2.5 concentrations at ARS and UA decreased from 156 to 75.5 µg m–3 and from 137 to 53.1 µg m–3, respectively, between the periods during (DWH) and after (AWH) the wheat harvest. The hysteresis of the PM2.5 peaks at UA confirmed the rural-to-urban migration of pollution. Additionally, we found high geo-accumulation index (Igeo) values for crustal elements at both sampling sites, indicating that the dust emissions originated from the WH. Between DWH and AWH, the share of soil dust in the PM2.5 decreased from 21.3% to 7.98% and from 9.40% to 6.75% at ARS and UA, respectively. Furthermore, the concentrations of the biomass burning markers Cl– and K+ increased from 5050 to 9370 µg g–1 and from 5480 to 8090 µg g–1 at ARS, respectively, and from 3360 to 6650 µg g–1 and from 3630 to 7500 µg g–1 at UA. Positive Matrix Factorization (PMF) identified six PM2.5 sources, viz., coal combustion (CC), vehicle exhaust (VE), industrial sources (ISs), biomass burning (BB), secondary inorganic aerosol (SIA), and fugitive dust (FD). FD dominated ARS during DWH and exhibited an increase at UA during AWH, and the contribution of BB at both sites rose between DWH and AWH, which can be ascribed to the burning of biomass for maize planting. Surprisingly, owing to the operation of harvesters and cultivators, the proportion of VE emissions was larger at ARS than UA. However, UA displayed a far greater percentage of industry-derived PM2.5, suggesting that local ISs should be controlled more strictly. Finally, the sizable share attributed to CC at both ARS and UA demonstrates the continued use of this fuel source, despite the governmental decree limiting it.

Phase-pure ε-iron carbide catalysts amenable to scale-up exhibit low CO2 selectivity and high stability in the FT reaction., The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO2 in the FT unit. Decreasing the CO2 release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure ε(′)-Fe2C catalysts exhibiting low CO2 selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO2. These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure ε(′)-Fe2C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.

This study analyzed the temporal variation of Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) of Hun River upstream forest in northeastern China and its correlation with climate parameters (temperature and precipitation) during the period of 2000–2009. We examined the interannual variation of forest, seasonal variation of forest and lag effects of climate variables (temperature and precipitation) on forest using simple regression and correlation. The objective of this paper was to compare the results of our research and previous researches and to show that the conclusions derived from broad-scale researches provided a direction of policy, but the local details were essential to local management. We found that the annual mean NDVI was significantly correlated with annual mean temperature. The forests studied in our research showed insignificant increase trends except for Fraxinus spp. forest. We concluded that the temperature was the limiting factor of vegetation growth in our study area and the forest which was in the core geographic area of its distribution was resilient to climate variation. When seasonal variation was examined, we found the largest increase trend of seasonal mean NDVI was in winter. The result was different from the outcome of previous research at national scale. There were 3 months lag effects of climate variables on vegetation of our study area in summer and autumn, which was consistent with researches at broad scales. The reasons of both difference and indifference were discussed in this paper. We also got information about tree species for local management using MODIS NDVI. The results of this work suggested that information from local scales would be important complements to researches at broad scales and were essential for local managers.

The theoretical and technique results of a 1D focusing linear Bragg–Fresnel optics working at 18 nm X-ray radiation are given in the present paper. A theoretical method describing its optical performances is introduced briefly, the parameters of the diffraction pattern are presented. The preparation of multilayer mirrors, the decision of X-ray absorber layer thickness and the fabrication process of the diffraction pattern are described. The studied results of thermal and chemical stabilities for Mo/Si multilayer structure are shown. Some measured results for the 1D focusing linear Bragg–Fresnel optics are given.

Stray light is non-imaging light that reach the optical system imaging plane. The non-imaging light can be received by detector if it is not effectively controlled, and stray light which directly irradiates on the detector has great influence on the imaging quality. Stray light can be effectively inhibited, if the outer baffle of space camera is designed optimally. Carbon fiber composite material is chosen as main material to meet requirements of a coaxial space optical system. The outer baffle should have advantages, such as lightweight, high stiffness and dimensional stability, etc. Using optimization design tools, the lightweight outer baffle is designed. And finite element method is used to check the structure. Development and test results show that the outer baffle with a diameter of 620mm and a total length of 1200mm only weighs 7.3kg. And the baffle's natural frequency reaches 88Hz, and it can satisfy the requirements of the space camera.

The thermal and chemical stabilities of Mo/Si multilayer structure used in Bragg-Fresnel optics were studied to get optimal technological parameters of pattern generation. Mo/Si multilayers were annealed at temperature ranging from 360 to 770 K, treated with acetone and 5 parts per thousand NaOH solution, and characterized by small-angle x-ray diffraction technique as well as x-ray photoelectron spectroscopy, and Olympus microscopy.

We study insertion losses of optical switch when the laser beam is propagating during the free space between two single mode fibers (SMFs) and the related assemblage challenges; Then a new packaging structure is developed for the hybrid-integration of free-space MOEMS (micro-opto-electro-mechanical systems) chip with a silicon micromachined submount to improve alignment accuracy. The submount is designed to accommodate various free-space MOEMS chips with minimal active optical alignment, thus reducing the packaging cost. The silicon submount has a central recess to place the MOEMS chip in, sixteen V-grooves for optical fibers, and micropits for micro ball lenses, all bulk micromachined at the same time by a single anisotropic wet etching step. A corner compensation technique is employed to prevent erosion of the convex corners, where different geometries meet. Through this assembling method, the fiber, micro ball lens can be aligned preciously thus reduced lateral and angular misalignment between them. Then total insertion losses can be decreased.

A theoretical method of focusing X-rays by the compound X-ray refractive lens is presented in this paper. The authors report their resent theoretical results including the material selection and structure parameters for such a device. As an example, a compound X-ray refractive lens with PMMA material is designed. The detailed fabrication process of the PMMA compound lens by LIGA technology is described. Moreover, some measured results by means of SEM are also shown. The structure height of one of the PMMA compound lens is measured to be 500μm.

In the present paper, a mask structure called adhering mask for excimer laser ablation is introduced. This mask is fabricated directly on the etched material, so it needn't a supporting chip and it thus has high transmission. Its absorber is made of gold and is fabricated by UV LIGA technology. Therefore the mask has more accurate structure and more smooth edges. This mask can fulfill the direct etching of the polymers by using a simpler optical system and can be a method of the mass production to some extent. The other mask is developed for X-ray lithography. It is made by UV LIGA process too. It consists of the substrate, the absorber and the supporter. The substrate is made of PI and the absorber is prepared by gold. The structure, fabrication process and experiment results of this mask are given.