Anthocyanins are known to have antioxidant activities. Their accumulation can be triggered by many chemical and environmental factors, including reactive oxygen species (ROS). However, the mechanism ...of ROS-induced anthocyanin accumulation and the role of anthocyanins in the response of Arabidopsis (Arabidopsis thaliana) to different stresses are largely unknown. Here, we study the cross-regulation between ROS and anthocyanin production. Ten Arabidopsis mutants covering the main anthocyanin regulatory and biosynthetic genes are systematically analyzed under ROS-generating stresses. We find that ROS triggers anthocyanin accumulation by up-regulating the anthocyanin late biosynthetic and the corresponding regulatory genes. The anthocyanin-deficient mutants have more endogenous ROS and are more sensitive to ROS-generating stresses while having decreased antioxidant capacity. Supplementation with cyanidin makes them less susceptible to ROS, with increased anthocyanin and reduced ROS accumulation. In contrast, pap1-D, which overaccumulates anthocyanins, shows the opposite responses. Gene expression analysis reveals that photosynthetic capacity is more impaired in anthocyanin-deficient mutants under high-light stress. Expression levels of ROS-scavenging enzyme genes are not correlated with the radical-scavenging activity in different mutants. We conclude that ROS are an important source signal to induce anthocyanin accumulation by up-regulating late biosynthetic and the corresponding regulatory genes and, as a feed-back regulation, anthocyanins modulate the ROS level and the sensitivity to ROS-generating stresses in maintaining photosynthetic capacity.
This paper is concerned with the distributed H ∞ filtering problem of discrete-time switched linear systems in sensor networks in face of packet dropouts and quantization. Specifically, due to the ...packet dropout phenomenon, the filters may lose access to the real-time switching signal of the plant. It is assumed that the maximal packet dropout number of switching signal is bounded. Then, a distributed filtering system is proposed by further considering the quantization effect. Based on the Lyapunov stability theory, a sufficient condition is obtained for the convergence of filtering error dynamics. The filter gain design is transformed into a convex optimization problem. In this paper, a quantitative relation between the switching rule missing rate and filtering performance is established. Furthermore, the upper bound of the switching rule missing rate is also calculated. Finally, the effectiveness of the proposed filter design is validated by a simulation study on the pulse-width-modulation-driven boost converter circuit. The impact of noise covariance, system dynamics, and network connectivity is studied, and some discussions are presented on how these parameters affect the filtering performance.
Structure and variability of internal tides (IT) and near‐inertial waves (NIW) on the continental slope of the northwestern South China Sea were investigated, based on 9‐month moored current ...observations from autumn to early summer in 2008 and 2009. The diurnal IT kinetic energy, dominant over that of semidiurnal tides, is found to exhibit apparent seasonal variability—strongest in summer and weakest in winter—whereas the semidiurnal variance remained nearly uniform throughout the observation period. Moreover, the diurnal IT were more coherent (i.e., phase‐locked to the astronomical forcing) than the semidiurnal constituents. Coherent diurnal variance accounts for about 40% of diurnal motions, but semidiurnal tides contain a much smaller fraction (10%) of coherent motions. Further analysis demonstrates that the diurnal IT are dominated by the first mode, whereas the semidiurnal tides show a variable multimodal structure: the second mode is dominant in summer and comparable to the first mode in spring and autumn, but the first mode predominates in winter. Multimodal semidiurnal IT are more influenced by varying stratification structures and background currents and thus exhibit highly incoherent and intermittent behavior, which may wash out seasonal variability during their long propagation from the generation source. The observed NIW are seasonally independent and comparable to the semidiurnal motions. During the passage of Typhoon Hagupit, however, the NIW became the most energetic component of the inertia‐gravity waveband motions. NIW energy and shear were significantly enhanced and exceeded tidal counterparts by a factor of 2 to 3 in the upper layer.
Key Points
Diurnal IT mainly in first‐mode are strong in summer and weak in winter
Semidiurnal IT in multimodal are highly incoherent (with 10% coherent energy)
Multimodal and incoherent semidiurnal IT are seasonally invariant
Although most deltas are expected to lose land due to climate change and urbanization, tide‐dominated deltas have been suggested to gain land. The processes of land change in such deltas are, ...however, not well understood, and tide‐dominated deltas with all their known morphological attributes have not been simulated before. Our Delft3D simulations successfully reproduce tide‐dominated delta morphology, and show that tide‐dominated deltas with seaward widening and stable channels, elongate tidal bars and a funnel shape form when bidirectional tidal flow occurs along the whole delta. In contrast, tide‐influenced but river‐dominated deltas protrude from shoreline, and are efficient at gaining land by mouth bar deposition and bifurcations. These differences are a function of tidal‐fluvial interactions expressed by month‐averaged seaward and lateral velocities. Identification of delta types is thus critical for predicting future land change. We propose morphological metrics to differentiate river‐ and tide‐dominated deltas and test metrics on 40 modern deltas.
Plain Language Summary
River deltas build extensive coastal lands that are one of the most economically and ecologically valuable environments on Earth. While many deltas lose land globally due to climate change and urbanization, deltas significantly influenced by tides are suggested to gain land. Here we utilize numerical modeling to explore the relative formative roles of river and tidal flows, and quantify how the land loss and gain processes differ in river‐ and tide‐dominated deltas. We show that deltas where tidal currents dominate throughout the whole delta build land with a low efficiency, because they form narrow elongate bars and seaward widening distributary channels. In contrast, deltas where tidal currents only dominate in seaward reaches are more efficient at gaining land as they build lobate deltas through mouth bar formation. We propose morphological criteria to distinguish river‐ and tide‐dominated deltas, so more accurate predictions of future land loss and gain can be made. We successfully test these criteria on 40 modern deltas, and show that identification of delta types and understanding the relative roles of river and tidal processes are critical for accurately predicting future change in deltas.
Key Points
Delft3D modeling quantifies the formative roles of river discharge and tidal amplitude in formation of river‐ versus tide‐dominated deltas
We simulate for the first time how river‐tide interactions lead to channel widening and tidal bar formation in tide‐dominated deltas
Understanding distinct land loss, gain, and formative processes in river‐ versus tide‐dominated deltas are critical for predicting future change
Anthocyanins are water-soluble pigments with antioxidant activities. In plants, multiple factors can trigger the accumulation of anthocyanins, including chemicals and environmental factors. Reactive ...oxygen species (ROS) are common by-products produced under different biotic and abiotic conditions and cause oxidative stress when accumulated at a high level in plant cells. This in turn leads to the production of anthocyanins. However, the mechanisms of ROS-induced anthocyanin accumulation and the role of anthocyanins in the response of plants to different stresses are largely unknown. We have recently reported the cross-regulation between ROS and anthocyanin production through analyzing ten Arabidopsis mutants covering the main anthocyanin regulatory and biosynthetic genes grown under different ROS-generating stresses. Here, we describe the general phenotypic response of anthocyanin mutants under normal and ROS-generating stress conditions, showing the changing levels of anthocyanin accumulation and their sensitivity to stresses. In addition, we propose a model that describes a particular gene interaction that highlights how the cross-regulation mechanisms between ROS and anthocyanin production are essential for plant resistance to various stresses through removing excessive ROS and maintaining photosynthetic capacity.
MXenes, a newly intriguing family of 2D materials, have recently attracted considerable attention owing to their excellent properties such as high electrical conductivity and mobility, tunable ...structure, and termination groups. Here, the Ti3C2Tx MXene is incorporated into the perovskite absorber layer for the first time, which aims for efficiency enhancement. Results show that the termination groups of Ti3C2Tx can retard the crystallization rate, thereby increasing the crystal size of CH3NH3PbI3. It is found that the high electrical conductivity and mobility of MXene can accelerate the charge transfer. After optimizing the key parameters, 12% enhancement in device performance is achieved by 0.03 wt% amount of MXene additive. This work unlocks opportunities for the use of MXene as potential materials in perovskite solar cell applications.
The 2D Ti3C2Tx additive can enlarge the grain size of the perovskite film due to the weak interactions between the termination groups (F and OH) and CH3NH3I. Due to these interactions, the perovskite nuclei generate around the additive and the number of nuclei is suppressed. Fewer nuclei make the grain size larger than that of the pristine film.
Birds (Aves) display high metabolic rates and oxygen consumption relative to mammals, increasing reactive oxygen species (ROS) formation. Although excess ROS reduces lifespan by causing extensive ...cellular dysfunction and damage, birds are remarkably long-lived. We address this paradox by identifying the constitutive activation of the NRF2 master antioxidant response in Neoaves (~95% of bird species), providing an adaptive mechanism capable of counterbalancing high ROS levels. We demonstrate that a KEAP1 mutation in the Neoavian ancestor disrupted the repression of NRF2 by KEAP1, leading to constitutive NRF2 activity and decreased oxidative stress in wild Neoaves tissues and cells. Our evidence suggests this ancient mutation induced a compensatory program in NRF2-target genes with functions beyond redox regulation-including feather development-while enabling significant metabolic rate increases that avoid trade-offs with lifespan. The strategy of NRF2 activation sought by intense clinical investigation therefore appears to have also unlocked a massively successful evolutionary trajectory.
This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that ...can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method. Keywords: Isolated grid, Primary frequency regulation capability, Small-signal stability, Laplace transfer, Parameter adjusting
Offshore marine engineering, offshore aquaculture, and offshore environmental protection require periodic offshore surveys. At present, the main means of offshore marine surveys are mooring buoys and ...marine survey ships. Anchored buoys are fixed in place for a long time, which affects the navigation of ships. Therefore, mooring buoys cannot be deployed over a large area with high density. The cost of marine survey ships is high, especially when multipoint synchronous marine surveys are needed, and marine survey ships cannot perform offshore surveys under bad sea conditions. A profile autonomous underwater vehicle system is developed to meet the requirements of multipoint short-term synchronous offshore surveys. It is a small, reusable, low-cost equipment designed to move up and down at a mooring position while measuring temperature, salinity, depth, and other quantities along a vertical water section. Profile autonomous underwater vehicles can be commanded remotely and report their measurements in near real-time via wireless telemetry. The time it takes for a profile AUV to move up and down can indicate the current velocity. Tests were carried out on a wharf and in offshore areas, and the results were satisfactory.
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