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We show that the semi-stable locus is the unique maximal open substack of the moduli stack of principal bundles over a curve that admits a schematic moduli space. For rank $2$ vector bundles it coincides with the unique maximal open substack that admits a separated moduli space, but for higher rank there exist other open substacks that admit separated moduli spaces., Comment: Improved exposition and fixed a minor computational error which unnecessarily restricted the genus of the curve for Theorem A. comments welcome!

The stoichiometric characteristics of plants are significantly affected by soil nutrients and moisture, which regulate photosynthesis. In wheat, they can be assessed to determine environmental adaptability. The selected spring wheat was investigated in a field experiment conducted from 2015 to 2017 in a semiarid area. The three treatments were (1) plastic-soil mulching (PMS), (2) gravel mulching (SM), and (3) without mulching (CK). The soil chemical properties and the net photosynthetic rate in flag leaves were recorded; the stoichiometric parameters of soil and flag leaves were calculated. The soil organic carbon (C) of PMS increased significantly in the 0–30-cm profile when compared with SM and CK, respectively. The soil nitrogen (N)/phosphorus (P) ratio of PMS increased in the filling stage when compared with SM and CK, respectively. The C/N ratio in flag leaves of wheat under PMS significantly decreased and increased compared with SM and CK at the filling stage during a wet year, respectively, and significantly decreased compared with CK during a drought year. The C/N and C/P ratios were significantly correlated between soil and wheat flag leaves in SM, and the net photosynthetic rates and the C/N, C/P, and N/P ratios of flag leaves under PMS and SM were also significantly correlated. The PMS treatment relieved soil nutrient limitations in flag leaves and increased the net photosynthetic rate by optimizing foliar C/N, C/P, and N/P ratios. This resulted in increased photosynthesis under drought conditions and significantly increased the yield and water-use efficiency.

The synthesis process of AF-Ali-PC MA and P(MMA-co-GMA) and the extra optical power loss caused by the Al electrode.

Integrated hole-sowing, fertilization, and plastic mulching techniques are common agronomic practices applied to collect rainwater and to improve rainwater utilization in semiarid rain-fed regions. However, little is known about the growth responses of tartary buckwheat (Fagopyrum tataricum L.) to the practices adopted in semiarid areas of Loess Plateau in Northwest China. To address the concerns, a long-term field experiment was conducted in 2015–2017. Four fertilization levels, namely, high fertilization level (N–P2O5–K2O: 120–90–60 kg ha−1, HF), moderate fertilization level (80–60–40 kg ha−1, MF), low fertilization level (40–30–20 kg ha−1, LF), and zero fertilization level (ZF), were applied to hole-sown tartary buckwheat with whole plastic mulching, in comparison to the control with no-mulching and zero fertilization (CK). Several key growth-influencing indicators were measured in the consecutive experimental years, including soil temperature (Ts), soil water storage (SWS), leaf area index (LAI), dry matter (DM), and grain yield. The results showed that in different precipitation years, 2015 (193 ± 23 mm), 2016 (149 ± 19 mm), and 2017 (243 ± 28 mm), the ZF, LF, MF, and HF treatments had the potential to optimize Ts in 0~25 cm soil layers (at 5 cm interval). The four treatments improved SWS in 0~300 cm soil layers by 3.5% and increased soil water consumption in the pre-anthesis period by 22.4%, compared with CK. Moreover, the four treatments shortened the pre-anthesis growth period by 0.4~5.4 d, while extended the post-anthesis growth period by 5.7~10.0 d, giving rise to an overall extension of 0.6~5.0 d for a whole growth period of tartary buckwheat. Furthermore, the ZF, LF, MF, and HF treatments increased LAI by 4.4~225.3% and DM weight by 41.5~238.0%. The rain yield of the four treatments was increased by 14.0~130.4%, and water use efficiency (WUE) was improved by 11.3~102.7%, especially for the LF treatment, compared with CK. The study indicated that the technique of hole-sowing and plastic mulching combined with a low fertilization rate was an effective measure for tartary buckwheat to optimize crop growth and to boost grain yield and WUE on semiarid lands.

In this paper we report the development and laboratory performance test of a high sensitivity 3C fiber laser geophone for borehole seismic acquisition application. First we are presenting the development of the fiber laser geophone and then testing its performance in third-party testing laboratory. The performances of the fiber laser geophone such as sensitivity, micro-seismic response, noise and temperature resistance are tested. Its performance is compared with high-temperature coil geophone simultaneously. The fiber laser geophone has advantages of wider bandwidth, better low-frequency and high-frequency micro-seismic response. These advantages are crucial for downhole micro-seismic monitoring geophysical imaging and micro-seismic monitoring.

Plastic mulching (PM) is regarded as a promising way to increase crop production. However, its reported that plastic mulching may decrease soil organic carbon content and been unfavorable for sustainable agricultural production. Confirmation of the effects of plastic mulching on soil water and organic carbon balances in a long term, including finding efficient ways to improve these balances, is crucial for the sustainability of agricultural production in semiarid rain-fed areas. We conducted field experiment (2010–2019), with spring maize and wheat as tested crops, using four treatments of plastic mulching (PM), plastic mulching with supplementary irrigation (PMI), plastic mulching with organic fertilizer application (PMO) and without mulching (CK). The results of this 10-year field experiment showed that PM with supplementary irrigation and organic fertilizer application not only significantly increased yield and Water productivity (WP) of wheat and maize, but also had a positive effect on soil water budget. The soil water budget of PMI, PMO and PM significantly increased by 120.4%, 96.1% and 105.8% in wheat and by 149.7%, 28.2% and 53.6% in maize, compared with CK, respectively. The improved soil water condition resulted in a significant increment of yield, PMI, PMO and PM increased yield by 122.8%, 89.7% and 67.0% for wheat, by 237.8%, 183.0% and 148.4% for maize, respectively, compared with CK. The 10 years of continuous PM significantly decreased soil organic carbon content (SOC) in 0–10, 10–20, 30–50 and 50–70 cm profiles by 22.5%, 19.1%, 15.6% and 15.3% for wheat, but had no significant effect for maize. The PMO significantly increased soil organic carbon content in 0–30 cm profiles for both wheat and maize, but the soil organic carbon budgets were negative for all four treatments, the PMO accelerated soil organic carbon loss for maize but had little effect for wheat compared with PM and CK. However, PMI, PMO and PM significantly increases crop bio-carbon production, resulted in the positive total carbon budget and significantly increased by 25.0, 15.0, 11.5 Mg ha−1 in wheat and 105.1, 74.1, 74.0 Mg ha−1 in maize, respectively, as compared with CK. These results suggested that the soil organic carbon budget differed for the two crops, also affected by water or organic carbon supplementation. A more appropriate crop rotation system with organic fertilizer application should be developed, to increase crop production and soil quality under plastic mulched condition in such semiarid rain-fed areas.

Double ridge and furrows with plastic mulching (PM), an effective drought-resistant farming technology, has been widely used in the semi-arid areas of China, and increased crop yields by more than 30%. However, where this technology has been applied in successive years, the annual balance of soil water has been affected and the risk of soil desiccation exacerbated. A 6-year field experiment had been conducted on the semiarid Loess Plateau to find a new mode of ecological security and economic efficiency under PM conditions. The two treatments were (i) PM with continuous maize cropping (PM-C) and (ii) PM with maize–fababean rotation (PM-R). The vertical variation of soil water along profile and the interannual variation of soil water, cumulative water consumption, biomass and yield, benefit and water economic yield were investigated. The results showed that the depth of soil water consumption of PM-C was extended downward by 60 cm from 2009 to 2014, but it did not vary in PM-R; the maximum depth of soil water consumption were 280 cm and 220 cm in PM-C and PM-R, respectively. Compared with the pre-seeding stage in 2009, soil water storage in the 0–300 cm depth in 2014-HA for PM-C decreased by 163.59 mm, comprising 5.21 mm in the 0–140 cm soil layer and 158.37 mm in the 140–300 cm layer. However, in the PM-R treatment, the soil water storage in the 0–300 cm depth in 2014-HA increased by 28.36 mm, resulting from an increase of 47.86 mm in the 0–140 cm soil layer and a decrease of 19.50 mm in the 140–300 cm layer. PM-R significantly improved crop water consumption in the post-flowering period, and the ratio of water consumption in post-flowering to total significantly increased by 19.54–51.09% (P

Plastic mulching increases crop yield and water use efficiency (WUE). However, its sustainability in regard to crop productivity and inter-annual soil water balance is widely doubted. This study comprises a long-term field experiment (2010–2019), with spring maize and wheat treated as materials, and two treatments of (1) whole field plastic mulching (PM), and (2) without mulching (CK). The results showed that the soil water storage in the sowing stage decreased significantly in the 100–300 cm profile after 10 years of maize planting in both PM and CK, but there was no significant difference between PM and CK. For wheat, PM on average increased soil water storage by 30.1 mm in the 0–300 cm profile, but CK decreased it by 28.7 mm in the sowing stage in 2019. These results indicated that soil water depletion was caused by maize water uptake not PM. The PM significantly (P

Sufficient nitrogen and shade may benefit photosynthetic down-regulation at elevated CO2 concentrations. Two levels of atmospheric CO2 400 and 760 μmol mol−1 were simulated using controlled environment open-top chambers, wheat (Triticum aestivum L) was grown at two N application rates (0 and 200 mg N kg−1 soil), and two photosynthetic photon fluxes (PPF, 100 and 60 % of solar irradiance). The increasing leaf N concentration, shade and N application extended the wheat developmental period and increased flag leaf fresh mass, water content, plant height and spike length by 11 d, 125, 126, 29 and 43 %, respectively. However, with sufficient N and elevated CO2, shade decreased dry mass, kilo-grain weight, instantaneous water use efficiency, grain water use efficiency and photosynthetic N use efficiency was increased by 30, 12, 2, 36 and 44 %, as compared with the unshaded treatment. Higher N application and shade increased N and chlorophyll concentration in flag leaves by 135 and 35 %, resulting in extended growth stage and increased plant and leaf water content, caused significant increments of plant height, grain number per spike and grain weight per spike under elevated CO2 as compared to N-deprived (0 mg N kg−1 soil) and unshaded treatment. Shade significantly increased leaf and plant water content, but did not affect wheat water and nitrogen use efficiency, which indicated that the decline of water content in flag leaves was a response of wheat to elevated CO2. The increment of leaf water status may extend the growth period to relieve photosynthesis acclimation at elevated CO2.