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National Research Foundation (NRF) Singapor

Formalization of complex analysis and matrix theory

This book discusses the formalization of mathematical theories centering on complex analysis and matrix theory, covering topics such as algebraic systems, complex numbers, gauge integration, the Fourier transformation and its discrete counterpart, matrices and their transformation, inner product spaces, and function matrices. The formalization is performed using the interactive theorem prover HOL4, chiefly developed at the University of Cambridge. Many of the developments presented are now integral parts of the library of this prover. As mathematical developments continue to gain in complexity, sometimes demanding proofs of enormous sizes, formalization has proven to be invaluable in terms of obtaining real confidence in their correctness. This book provides a basis for the computer-aided verification of engineering systems constructed using the principles of complex analysis and matrix theory, as well as building blocks for the formalization of more involved mathematical theories

VB₁ Promoted Green Synthesis of Chalcones and Its Neuroprotection Potency Evaluation

For the first time, thiamine hydrochloride (VB1) has been employed as a catalyst for the synthesis of chalcones by metal-free Claisen–Schmidt condensation. Such an environmentally benign approach has several advantages such as a wide range of functional groups tolerance, a high yield of products, and the recoverability of this catalyst. Moreover, this unprecedented methodology enables the synthesis of the pharmaceutically important molecule 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (3f) and its derivatives. Moreover, 3f and its derivatives were screened for their preliminary in vitro neuroprotective activity against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced apoptosis in SH-SY5Y cell lines. Most of the compounds exhibited the neuroprotective activity, and one of the prepared chalcones (3s), which incorporates prenyl moiety, showed the most potency by decreasing the expression of cleaved caspase-3, cleaved caspase-9, Bax, and p53 protein

Impacts of growth temperature, water deficit and heatwaves on carbon assimilation and growth of cotton plants (Gossypium hirsutum L.)

Increased variability in growing season climates continues to threaten the growth and yields of many crops. The impacts of individual climate stress conditions on crops has been documented frequently, yet how crops respond to multiple abiotic stress components is less well understood. Here, we report on the main and interactive effects of growth temperature, water deficit and a heatwave on leaf physiology and biomass production of cotton plants (Gossypium hirsutum L.). Plants were raised under two day/night growth temperature regimes (28/18 °C and 32/22 °C) and their corresponding nocturnal warming (+4 °C) scenarios (i.e. 28/22 °C and 32/26 °C). Following the emergence of the first square (flower bud), plants were subjected to two water treatments (well-watered and water deficit) until the beginning of the flowering stage, and then half of the plants in all temperature treatments were exposed to a 5-day heatwave treatment (40/26 °C). We found that elevated growth temperature increased growth rate (as defined by plant height) and leaf-level carbon gain, but decreased total aboveground biomass. Water deficit stress decreased leaf level carbon gain and biomass, but these impacts were generally less pronounced. Nocturnal warming moderately decreased leaf carbon gain for plants grown under the cool temperature regime (i.e. 28/18 °C), but not the warm temperature regime (i.e. 32/22 °), and its impacts on biomass were also thermal regime specific. In contrast, leaf carbon gain was promoted by the heatwave under the cool daytime temperature treatment, but not the warm daytime temperature treatment. However, total aboveground biomass was less affected by the heatwave due to high resilience of gas exchange, although there was decreased fruit biomass. Overall, both short- and long-term increases in daytime temperature decreased cotton fruit biomass, while nocturnal warming had limited capacity to buffer that impact. Moderate soil water deficit will not strongly reduce carbon gain and growth. This study adds to the knowledge regarding the response of cotton plants to climate change and underscores the complexity of plant response to multiple environmental factors.This work was supported by the Cotton Research Development Corporation (CRDC; CSP1501 and CSP1804)

Photosynthetic acclimation of an evergreen broadleaved shrub (Ammopiptanthus mongolicus) to seasonal climate extremes on the Alxa Plateau, a cold desert ecosystem

Key message: Survival of Ammopiptanthus mongolicus in a cold desert environment is facilitated by high photosynthesis rates in spring and summer, and efficient photoprotective strategies in winter cold. Woody evergreen plants inhabiting cold desert ecosystems must retain their foliage amidst chronically dry conditions and large seasonal temperature variations. To understand the strategies enabling survival of evergreens in these environments, we monitored seasonal changes in foliar gas exchange and photosynthetic traits of Ammopiptanthus mongolicus, an evergreen broadleaved shrub native to the cold desert of northwestern China. We found that photosynthesis was relatively higher in spring and summer and lower in fall and winter. Transitioning from spring to summer, A. mongolicus maintained high photosynthetic capacity (Amax). Transitioning into fall, the Amax and maximum stomatal conductance (gsmax) decreased, while the relative stomatal limitation to photosynthesis (Ls) increased. In winter, A. mongolicus decreased Amax, maximum quantum efficiency of photosystem II (Fv/Fm), maximum RuBisCo carboxylation rates (Vcmax), maximum RuBP regeneration rates (Jmax), and photosynthetic nitrogen-use efficiency (PNUEmax) relative to other seasons. Collectively, these results suggest that A. mongolicus adapts physiologically to maximize carbon assimilation during spring and summer, and to maximize foliar resistance to cold stress at the expense of photosynthesis in winter. Foliage was protected against photo-oxidative damage during temperature extremes in winter by dark-sustained thermal energy dissipation. Overall, our study reveals that multiple photosynthetic adjustments, varying among the seasons, enable the survival of cold desert evergreens

Petroleum geological features and hydrocarbon enrichment of Linhe Depression in Hetao Basin, NW China

Based on paleogeomorphology, drilling and seismic data, this paper systematically studies the structural and sedimentary evolution, source rock characteristics, reservoir characteristics and formation mechanism, hydrocarbon accumulation model and enrichment law in the Linhe Depression of the Hetao Basin, NW China. The Hetao Basin mainly experienced three stages of evolution, namely, weak extensional fault depression, strong extensional fault depression and strike-slip transformation, giving rise to four positive structural belts (Jilantai, Shabu, Nalinhu and Xinglong), which are favorable areas for oil and gas accumulation. The two main saline lacustrine source rocks, Lower Cretaceous Guyang Formation and Oligocene Linhe Formation, are characterized by high sulfur content, rich algae, early maturity, early expulsion, and wide oil generation window. The large structural transition belt in the intermountain area around the Hetao Basin controls the formation of large-scale braided river delta deposits, which are characterized by high quartz content (50%–76%), long-term shallow burial and weak compaction, low cement content, and good reservoir properties in delta front sandbody. The burial depth of the effective Paleogene reservoirs is predicted to reach 8000 m. Three hydrocarbon accumulation models, nose-uplift near sag, buried hill surrounding sag, fault nose near source rock, are constructed. The law of hydrocarbon accumulation in the Linhe Depression is finally clarified as follows: near-source around the depression is the foundation, high-quality thick reservoir is the premise, good tectonic setting and trap conditions are the key

3D Sodiophilic Ti3C2MXene@g-C3N4Hetero-Interphase Raises the Stability of Sodium Metal Anodes

Owing to several advantages of metallic sodium (Na), such as a relatively high theoretical capacity, low redox potential, wide availability, and low cost, Na metal batteries are being extensively studied, which are expected to play a major role in the fields of electric vehicles and grid-scale energy storage. Although considerable efforts have been devoted to utilizing MXene-based materials for suppressing Na dendrites, achieving a stable cycling of Na metal anodes remains extremely challenging due to, for example, the low Coulombic efficiency (CE) caused by the severe side reactions. Herein, a g-C3N4layer was attached in situ on the Ti3C2MXene surface, inducing a surface state reconstruction and thus forming a stable hetero-interphase with excellent sodiophilicity between the MXene and g-C3N4to inhibit side reactions and guide uniform Na ion flux. The 3D construction can not only lower the local current density to facilitate uniform Na plating/stripping but also mitigate volume change to stabilize the electrolyte/electrode interphase. Thus, the 3D Ti3C2MXene@g-C3N4nanocomposite enables much enhanced average CEs (99.9% at 1 mA h cm-2, 0.5 mA cm-2) in asymmetric half cells, long-term stability (up to 700 h) for symmetric cells, and stable cycling (up to 800 cycles at 2 C), together with outstanding rate capability (up to 20 C), of full cells. The present study demonstrates an approach in developing practically high performance for Na metal anodes

Impacts of growth temperature, water deficit and heatwaves on carbon assimilation and growth of cotton plants (Gossypium hirsutum L.)

Increased variability in growing season climates continues to threaten the growth and yields of many crops. The impacts of individual climate stress conditions on crops has been documented frequently, yet how crops respond to multiple abiotic stress components is less well understood. Here, we report on the main and interactive effects of growth temperature, water deficit and a heatwave on leaf physiology and biomass production of cotton plants (Gossypium hirsutum L.). Plants were raised under two day/night growth temperature regimes (28/18 °C and 32/22 °C) and their corresponding nocturnal warming (+4 °C) scenarios (i.e. 28/22 °C and 32/26 °C). Following the emergence of the first square (flower bud), plants were subjected to two water treatments (well-watered and water deficit) until the beginning of the flowering stage, and then half of the plants in all temperature treatments were exposed to a 5-day heatwave treatment (40/26 °C). We found that elevated growth temperature increased growth rate (as defined by plant height) and leaf-level carbon gain, but decreased total aboveground biomass. Water deficit stress decreased leaf level carbon gain and biomass, but these impacts were generally less pronounced. Nocturnal warming moderately decreased leaf carbon gain for plants grown under the cool temperature regime (i.e. 28/18 °C), but not the warm temperature regime (i.e. 32/22 °C), and its impacts on biomass were also thermal regime specific. In contrast, leaf carbon gain was promoted by the heatwave under the cool daytime temperature treatment, but not the warm daytime temperature treatment. However, total aboveground biomass was less affected by the heatwave due to high resilience of gas exchange, although there was decreased fruit biomass. Overall, both short- and long-term increases in daytime temperature decreased cotton fruit biomass, while nocturnal warming had limited capacity to buffer that impact. Moderate soil water deficit will not strongly reduce carbon gain and growth. This study adds to the knowledge regarding the response of cotton plants to climate change and underscores the complexity of plant response to multiple environmental factors