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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!

Bei einem Moduliproblem, das durch einen algebraischen Stack beschrieben wird, ist es oft gar nicht so schwer zu zeigen, dass ein offener Unterstack des algebraischen Stacks einen guten Modulraum zulässt. In dieser Arbeit liefern wir zwei Beispiele, in denen alle offenen Unterstacks charakterisiert werden können: Modulstacks von Rang 2-Vektorbündeln über einer Kurve. Quotientenstacks für Gm-Aktionen. Ein wesentlicher Bestandteil des Beweises ist die Arbeit von Jarod Alper, Daniel Halpern-Leistner und Jochen Heinloth über die Existenz guter Modulräume für algebraische Stacks., Given a moduli problem described by an algebraic stack, usually the algebraic stack itself does not admit a proper good moduli space, but some of its open substacks would do. In this thesis we provide two examples where all such open substacks can be characterized: < Moduli stack of rank 2 vector bundles over a curve. Quotient stack for Gm-actions. A major ingredient of the proof is the recent work of Jarod Alper, Daniel Halpern-Leistner and Jochen Heinloth on the existence of good moduli spaces for algebraic stacks.

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.

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.