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Structural phase transitions serve as the basis for many functional applications including shape memory alloys (SMAs), switches based on metal-insulator transitions (MITs), etc. In such materials, lattice incompatibility between transformed and parent phases often results in a thermal hysteresis, which is intimately tied to degradation of reversibility of the transformation. The non-linear theory of martensite suggests that the hysteresis of a martensitic phase transformation is solely determined by the lattice constants, and the conditions proposed for geometrical compatibility have been successfully applied to minimizing the hysteresis in SMAs. Here, we apply the non-linear theory to a correlated oxide system (V 1− x W x O 2 ), and show that the hysteresis of the MIT in the system can be directly tuned by adjusting the lattice constants of the phases. The results underscore the profound influence structural compatibility has on intrinsic electronic properties, and indicate that the theory provides a universal guidance for optimizing phase transforming materials. The effect of the lattice degrees of freedom on the metal-insulator transition of VO 2 remains a topic of debate. Here the authors show that the lattice compatibility of the high temperature tetragonal phase and the low-temperature monoclinic phase strongly influences the electronic transition, as manifested in the tunability of its hysteresis via chemical substitution.

The Paleotethyan tectonic history of northeast Tibet remains hotly debated, particularly regarding the nature of the Jinsha suture. Different interpretations of the Jinsha suture lead to different tectonic reconstructions of northeast Tibet, southern Eurasian continent. We identified three tectonic units along the western segment of the Jinsha suture in the Yushu–Zhiduo region: the Bayan Har–Songpan–Garzê fold belt (BSB), the Yushu mélange, and the eastern portion of the Qiangtang block (EQ). New geochemical and geochronological studies help to identify a Triassic continental magmatic arc (the Yushu arc) that developed upon the EQ and that is geochemically similar to magmatism in the Yidun arc. Structural studies, combined with 40Ar/39Ar analyses, reveal a complex deformational history of the Yushu–Zhiduo region: earlier‐stage top‐to‐the‐north asymmetrical fabrics are preserved exclusively in the Yushu mélange, which yields a phengite 40Ar/39Ar age of 230.5 ± 0.8 Ma; later‐stage orthogonal fabrics developed in the BSB and EQ (superposed upon the earlier fabrics in the Yushu mélange), likely resulted from a collision between the BSB and the Yushu arc that continued until ∼195 Ma. The structural patterns and deformation history of Yushu arc region are comparable with those recorded in the Yidun arc region. Thus, the previously defined Jinsha suture should be subdivided into western and southern segments. The western Jinsha suture is continuous with the Garzê‐Litang suture, while the southern Jinsha‐Ailaoshan suture marks the site of the closure of several intracontinental rift basins that have likely been overprinted by intra or back‐arc extension. Key Points The Yidun and Yushu arcs, northeast Tibet, have identical tectonothermal history The southern Jinsha‐Ailaoshan suture doesn't represent a mature ocean The western Jinsha suture extends eastward and connects to Garze‐Litang suture

The beneficial roles of melatonin in plants have been widely reported, but its effect on photosynthesis under drought stress is not clear. In the study, correlated tests were performed to discover melatonin part on photosynthesis in maize ( Zea mays L.) seedlings leaves during drought stress. The results showed that melatonin application can mitigate the drought stress-induced damage by protecting chloroplast membrane structure and physiological function. Under drought stress condition, melatonin-treated plants maintained higher photosynthetic rate ( P n ), stomatal conductance ( g s ), intercellular CO 2 concentration ( C i ) and transpiration rate ( T r ). The photosystem I (PSI) reaction central proteins-encoding genes ( psaA / psaB ), cytochrome b6/f complex subunits-encoding genes ( petA / petB ), photosystem II (PSII) reaction central proteins-encoding genes ( psbA / psbB ), PSII antenna proteins-encoding genes ( psbC / psbD ) and photosynthetic enzymes (phosphoenolpyruvate carboxylase (PEPC), pyruvate phosphate dikinase (PPDK), NADP-malic enzyme (NADP-ME) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)) activity were enhanced. These evidences suggested that exogenous melatonin significantly increased the effective quantum yield and electron transport rate on PSII and PSI, but also decreased energy dissipation and donor and acceptor side impairment on PSI. To sum up, our study provides new insights to further investigate melatonin regulation mechanism on enhancement maize seedings drought tolerance.

Melatonin is known to exert protective effects in maize against drought stress, but the knowledge regarding interaction among the melatonin, photosynthetic efficiency, ascorbate–glutathione cycle still remains elusive. Two contrasting maize ( Zea mays L.) genotypes, SD609 (drought-tolerant) and SD902 (drought-sensitive), were subjected to moderate and severe drought stress along with 100 μM melatonin treatment. Exogenous melatonin increased fluorescence curve levels for both genotypes under drought stress, and higher in SD609 than SD902. In both genotypes, melatonin application also significantly increased the photochemical efficiency of photosystem II (PSII), the effective quantum yield of PSII and photosystem I (PSI), and the electron transport rate between PSII and PSI under drought stress, but it decreased the quantum yield of energy dissipation and the donor side and acceptor side impairment of PSI under drought stress, regardless of stress severity. Exogenous melatonin also contributed to the reduction of membrane damage under drought stress, as reflected by significantly decreased levels of MDA, superoxide anions and H 2 O 2 of both genotypes exposed to drought. Furthermore, melatonin treatment increased enzyme activity in AsA–GSH cycle, and upregulated the genes expression of related enzymes in AsA–GSH cycle. The effects of melatonin were more pronounced in SD609 than SD902. Collectively, these results indicated that exogenous melatonin application increased photosynthetic electron transport rate and accelerated the AsA–GSH cycle, which are factors that play an important role in drought tolerance in maize. The beneficial effect of melatonin on the drought-tolerance SD609 was more obvious.

The impact of the axial displacement of a floating impeller in a vortex pump on performance and axial force was investigated through numerical simulations, validated by experimental tests. Simulations were conducted to calculate axial forces at various impeller positions under different operating conditions. The results indicate that increasing the axial displacement of the impeller reduces both the pump head and efficiency. Compared with inlet axial clearance, reducing the outlet axial clearance improves energy conversion while having a smaller effect on head performance. At lower flow rates, the pressure difference between the balance cavities on both sides of the floating impeller increases, leading to a higher axial force. Adjusting the axial position of the impeller can effectively reduce axial force, optimising both its magnitude and direction to help restore the impeller to a central position. The balance cavity modifies the static pressure distribution in the high-pressure region of the impeller, further minimising extreme axial force values in this region. However, as flow rate increases, the influence of the balance cavity diminishes.

The ability to use remotely sensed ocean color data to parameterize biogenic heating in a coupled ocean–atmosphere model is investigated. The model used is a hybrid coupled model recently developed at the Earth System Science Interdisciplinary Center (ESSIC) by coupling an ocean general circulation model with a statistical atmosphere model for wind stress anomalies. The impact of the seasonal cycle of water turbidity on the annual mean, seasonal cycle, and interannual variability of the coupled system is investigated using three simulations differing in the parameterization of the vertical attenuation of downwelling solar radiation: (i) a control simulation using a constant 17-m attenuation depth, (ii) a simulation with the spatially varying annual mean of the satellite-derived attenuation depth, and (iii) a simulation accounting for the seasonal cycle of the attenuation depth. The results indicate that a more realistic attenuation of solar radiation slightly reduces the cold bias of the model. While a realistic attenuation of solar radiation hardly affects the annual mean and the seasonal cycle due to anomaly coupling, it significantly affects the interannual variability, especially when the seasonal cycle of the attenuation depth is used. The seasonal cycle of the attenuation depth interacts with the low-frequency equatorial dynamics to enhance warm and cold anomalies, which are further amplified via positive air–sea feedbacks. These results also indicate that interannual variability of the attenuation depths is required to capture the asymmetric biological feedbacks during cold and warm ENSO events.

To clarify how the components of the entire photosynthetic electron transport chain in response to drought stress in maize. The activities of photosystem II (PSII), photosystem I (PSI), and the electron transport chain between PSII and PSI of maize were investigated by prompt fluorescence (PF), delayed fluorescence (DF) and 820 nm modulated reflection (MR). Maize ( Zea mays L.) plants were subjected to different levels of soil water availability including control, moderate and severe drought stress. A significant decrease in ϕ E 0 , Ψ 0 and PI ABS was found in maize treated with moderate drought stress. A significant increase in ABS/RC was observed, but there were no significant change in the fast MR phase and the amplitude of DF under moderate drought stress compared to the control. Under severe drought stress, the exchange capacity between Q A to Q B , reoxidation capacity of plastoquinol, and the oxidation and re-reduction rates of PC and P 700 all decreased. These results demonstrated that moderate drought stress reduced the photochemical activity of PSII from Q A to PQH 2 , while the photochemical activity of PSI was unscathed. However, severe drought stress inhibited the entire electron transport chain from the donor side of PSII to PSI-end electron acceptors. In addition, the photochemical activity of PSII is more sensitive to drought stress than PSI.

To improve the prediction accuracy of the surrogate model and reduce the calculation cost for hydraulic optimization design of centrifugal pump impeller, an inverse design and optimization method based on adaptive proper orthogonal decomposition (APOD) hybrid model was proposed. Initial samples were designed by perturbing blade control parameters of the original model. The samples were classified using the K-means clustering algorithm, and the adaptive samples were selected according to the category of the objective sample. The snapshot set is composed of blade shape parameters and the CFD flow field data in impeller, which is decomposed into a linear combination of orthogonal bases by the proper orthogonal decomposition (POD) method to predict the objective parameters. According to the objective load distribution, the low specific speed centrifugal pump was inversely designed by using the APOD model, and its initial blade was obtained. And then, the flow field corresponding to disturbed blade shape was predicted using the APOD method, so as to evaluate the gradient of the objective function to design variables. Finally, the initial blade was optimized by the gradient descent method. The results show that the APOD hybrid model method can be employed to accomplish the blade inverse design and the flow field prediction in the optimization design of centrifugal impeller, which significantly reduces the numerical calculation cost and improves the accuracy of the flow field prediction.

Melatonin plays an important role in the enhancement of plant tolerance to drought stress. The underlying mechanisms of this melatonin-induced protection of the photosynthetic apparatus against drought stress are still not fully understood in maize ( Zea mays L.). This study investigated the effects of 100 and 200 μM exogenous melatonin additions on the photosynthetic electron transport process in maize seedlings under drought stress. The chlorophyll a fluorescence transient (OJIP) and modulated 820 nm reflection (MR) analysis showed that drought stress damaged the donor and acceptor side of photosystem II (PSII). Furthermore, the function of PSII reaction centers and the quantum yields of PSI and PSII were significant reduced. These fluorescence parameters were restored in melatonin-treated plants. Energy conversion analysis indicated that melatonin-treated plants maintained a stronger ability to ensure high photosynthetic capacity, as evidenced by higher PSI photochemical quantum yield Y(I) and PSII photochemical quantum yield Y(II). Melatonin treatment decreased the regulated energy dissipation Y(NPQ) and non-regulated energy dissipation Y(NO) in PSII. Moreover, melatonin treatment mitigated the limitations of both the acceptor-side and donor-side of PSI under drought stress, as indicated by lower PSI acceptor side limitation Y(NA) and PSI donor side limitation Y(ND). In addition, 100 μM melatonin was the more effective concentration to alleviate the damage to the photosynthetic apparatus. Thus, exogenous melatonin alleviated the drought stress-induced damage of the photosynthetic apparatus in maize by improving the photosynthetic electron transport efficiency between both photosystems and by enhancing the quantum yields of PSI and PSII photochemistry.

A new approach to retrieving air temperature from land surface temperature is presented. The new method is based on thermodynamics. Two important parameters, namely crop water stress index and aerodynamic resistance, were used to build a quantitative relationship between the land surface temperature and the ambient air temperature. The method was applied using MODIS satellite data for a location situated in the North China Plain. Comparing the measurement values at meteorological stations with air temperature, derived by the method for certain pixels, indicates that derived values can be obtained within an accuracy of 3 degrees C for more than 80% of data processed. Sensitivity studies also suggest that inaccuracies associated with measurement error in the model variables are also within the 3 degrees C range. [PUBLICATION ABSTRACT]