Comparison of photosynthetic responses between haptophyte Phaeocystis globosa and diatom Skeletonema costatum under phosphorus limitation.

The diatom Skeletonema costatum and the haptophyte Phaeocystis globosa often form blooms in the coastal waters of the South China Sea. Skeletonema costatum commonly dominates in nutrient enrichment coastal waters, whereas P. globosa starts flourishing after the diatom blooms when phosphorus (P) is limited. Therefore, P limitation was proposed to be a critical factor affecting diatom-haptophyte transition. To elucidate the tolerance to P limitation in P. globosa compared with S. costatum, the effect of P limitation on their photosystem II (PSII) performance was investigated and their photosynthesis acclimation strategies in response to P limitation were evaluated. P limitation did not affect the growth of P. globosa over 7 days but decreased it for S. costatum. Correspondingly, the PSII activity of S. costatum was significantly inhibited by P limitation. The decline in PSII activity in S. costatum under P limitation was associated with the impairment of the oxygen-evolving complex (the donor side of PSII), the hindrance of electron transport from QA - to QB (the acceptor side of PSII), and the inhibition of electron transport to photosystem I (PSI). The 100% decrease in D1 protein level of S. costatum after P limitation for 6 days and PsbO protein level after 2 days of P limitation were attributed to its enhanced photoinhibition. In contrast, P. globosa maintained its photosynthetic activity with minor impairment of the function of PSII. With accelerated PSII repair and highly increased non-photochemical quenching (NPQ), P. globosa can avoid serious PSII damage under P limitation. On the contrary, S. costatum decreased its D1 restoration under P limitation, and the maximum NPQ value in S. costatum was only one-sixth of that in P. globosa. The present work provides extensive evidence that a close interaction exists between the tolerance to P limitation and photosynthetic responses of S. costatum and P. globosa.

Blooms of diatom and dinoflagellate associated with nutrient imbalance driven by cycling of nitrogen and phosphorus in anaerobic sediments in Johor Strait (Malaysia).

Coastal eutrophication is one of the pivotal factors driving occurrence of harmful algal blooms (HABs), whose underlying mechanism remained unclear. To better understand the nutrient regime triggering HABs and their formation process, the phytoplankton composition and its response to varying nitrogen (N) and phosphorus (P), physio-chemical parameters in water and sediment in Johor Strait in March 2019 were analyzed. Surface and sub-surface HABs were observed with the main causative species of Skeletonema, Chaetoceros and Karlodinium. The ecophysiological responses of Skeletonema to the low ambient N/P ratio such as secreting alkaline phosphatase, regulating cell morphology (volume; surface area/volume ratio) might play an important role in dominating the community. Anaerobic sediment iron-bound P release and simultaneous N removal by denitrification and anammox, shaped the stoichiometry of N and P in water column. The decrease of N/P ratio might shift the phytoplankton community into the dominance of HABs causative diatoms and dinoflagellates.

Size-Controlled Polarization Retention and Wall Current in Lithium Niobate Single-Crystal Memories.

Highly conductive domain walls in insulating ferroelectric LiNbO3 (LNO) single-crystal thin films with atomic smoothness are attractive for use in high-density integration of the ferroelectric domain wall random access memory (DWRAM) because of their excellent reliability and high read currents. However, downscaling of the memory size to the nanoscale could cause poor polarization retention. Understanding the size-dependent electrical performance of a memory cell is therefore crucial. In this work, highly insulating X-cut LNO thin films were bonded to SiO2/Si wafers and lateral mesa-like cells were fabricated on the film surfaces, where contact occurred with two-sided electrodes along the polar z-axis. Under application of an in-plane electric field above a coercive field (Ec), the domain within each memory cell was switched to be antiparallel to the unswitched referencing domain at the bottom; this resulted in the formation of a conducting domain wall, which enables the nondestructive readout strategy of the DWRAM. The cell, which has a lateral length (l) above a critical size (l0) of 105 nm, is found to be a mixture of two phases across the cell area. The inner area of the cell suffers from poor polarization retention because Ec = 150 kV/cm, as demonstrated by in-plane piezoresponse force microscopy imaging. In comparison, the outer periphery domains, which have lengths of 70 nm (∼l0/2), show good retention but require a much higher Ec of 785 kV/cm. The relevant physics is discussed as phase reconstruction occurs after release of the in-plane compressive strain near the outer regions; the results show good agreement with those of one-dimensional thermodynamic calculations and phase-field simulations. The measured current-voltage curves demonstrated a sudden enhancement of the wall current across the cell when l < l0, thus implying higher readout wall currents and better retention for the DWRAM at higher storage densities.

Degradation of malathion in the solution of acetyl peroxyborate activated by carbonate: Products, kinetics and mechanism.

The degradation process of malathion in the acetyl peroxyborate (APB) solution of different APB/malathion molar ratio and in the carbonate-activated APB (APB/CO32-) solution of different pH was studied by 31P NMR technology. In the APB solution, all malathion could be degraded in 47.5 min when the molar ratio of APB/malathion was 60. CO32- could effectively activate APB to degrade all malathion in 10 min at pH of 10 when APB/malathion was 10, which was obviously higher than in APB solution. 1O2, •O2-, •OH and carbon-centered radicals (RC•) could be produced in the APB/CO32- solution, and the degradation of malathion was mainly affected by RC•. The degradation mechanism of malathion in the APB/CO32- solution was proposed based on the research results of malathion degradation process by 31P NMR and active species quenching test, which involves two steps: the first step is the oxidation of malathion to malaoxon by RC•, and the second step is the hydrolysis of malaoxon to dimethyl phosphate via hydroxyl anions nucleophilic addition.

Energy-Efficient Ferroelectric Domain Wall Memory with Controlled Domain Switching Dynamics.

High readout domain-wall currents in LiNbO3 single-crystal nanodevices are attractive because of their application in a ferroelectric domain wall random access memory (DWRAM) to drive a fast memory circuit. However, the wall current at a small read voltage would increase nonlinearly at a much higher write voltage, which could cause high energy consumption. Here, we resolved this problem by controlling the two-step domain forward growth within a ferroelectric mesa-like cell that was formed at the surface of an X-cut LiNbO3 single crystal. The mesa-like cell contacts two side Pt/Ni electrodes that extend over the cell surface by 90 nm for the generation of an in-plane inhomogeneous electric field. The domain forward growth processes at first in the formation of an inclined charged 180° domain to span the in-plane electrode gap under a write voltage of 5 V in a large readout wall current, and then, the domain expands fully throughout the entire cell in the formation of a neutral 180° wall to reduce the wall current by 10 times at a higher write voltage of 6 V. Meantime, the domain below the mesa-like cell in an opposite orientation is unchanged to serve as the reference. A higher wall current at a lower read voltage and a lower wall current at a higher write voltage can satisfy both requirements of low energy consumption and fast operation speeds for the DWRAM.

Nonvolatile ferroelectric field-effect transistors.

Future data-intensive applications will have integrated circuit architectures combining energy-efficient transistors, high-density data storage and electro-optic sensing arrays in a single chip to perform in situ processing of captured data. The costly dense wire connections in 3D integrated circuits and in conventional packaging and chip-stacking solutions could affect data communication bandwidths, data storage densities, and optical transmission efficiency. Here we investigated all-ferroelectric nonvolatile LiNbO3 transistors to function through redirection of conducting domain walls between the drain, gate and source electrodes. The transistor operates as a single-pole, double-throw digital switch with complementary on/off source and gate currents controlled using either the gate or source voltages. The conceived device exhibits high wall current density and abrupt off-and-on state switching without subthreshold swing, enabling nonvolatile memory-and-sensor-in-logic and logic-in-memory-and-sensor capabilities with superior energy efficiency, ultrafast operation/communication speeds, and high logic/storage densities.

Identification of Early Salinity Stress-Responsive Proteins in Dunaliella salina by isobaric tags for relative and absolute quantitation (iTRAQ)-Based Quantitative Proteomic Analysis.

Salt stress is one of the most serious abiotic factors that inhibit plant growth. Dunaliella salina has been recognized as a model organism for stress response research due to its high capacity to tolerate extreme salt stress. A proteomic approach based on isobaric tags for relative and absolute quantitation (iTRAQ) was used to analyze the proteome of D. salina during early response to salt stress and identify the differentially abundant proteins (DAPs). A total of 141 DAPs were identified in salt-treated samples, including 75 upregulated and 66 downregulated DAPs after 3 and 24 h of salt stress. DAPs were annotated and classified into gene ontology functional groups. The Kyoto Encyclopedia of Genes and Genomes pathway analysis linked DAPs to tricarboxylic acid cycle, photosynthesis and oxidative phosphorylation. Using search tool for the retrieval of interacting genes (STRING) software, regulatory protein⁻protein interaction (PPI) networks of the DAPs containing 33 and 52 nodes were built at each time point, which showed that photosynthesis and ATP synthesis were crucial for the modulation of early salinity-responsive pathways. The corresponding transcript levels of five DAPs were quantified by quantitative real-time polymerase chain reaction (qRT-PCR). These results presented an overview of the systematic molecular response to salt stress. This study revealed a complex regulatory mechanism of early salt tolerance in D. salina and potentially contributes to developing strategies to improve stress resilience.

Di-(2-ethylhexyl) Phthalate Exposure Modulates Antioxidant Enzyme Activity and Gene Expression in Juvenile and Adult Daphnia magna.

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer used in the polyvinyl chloride industry worldwide. DEHP exists in the aquatic environments for decades. However, the toxicological effects of DEHP to aquatic organisms have not been adequately researched. We investigated acute toxicity, oxidative damage, antioxidant enzyme activities, and gene expression patterns of antioxidant enzymes in juvenile and adult Daphnia magna exposed to DEHP. We found that the median lethal concentrations (LC50) of DEHP for juveniles exposed for 24 and 48 h were 0.83 and 0.56 mg L-1, respectively. The LC50 of DEHP in adults exposed for 24 and 48 h were 0.48 and 0.35 mg L-1. Daphnia magna that was exposed to DEHP had increased malondialdehyde levels for 24 h and lower total antioxidant capacity compared with the control. Activity levels of antioxidant enzymes superoxide dismutase and phase II detoxifying enzyme glutathione S-transferases were significantly higher upon initial exposure for 24 h, and enzyme activity was then diminished at high concentrations and prolonged exposure for 48 h. Gene expression levels of cat and gst were notably reduced or increased upon DEHP exposure. These findings suggest that DEHP can cause biochemical and physiological effects in juvenile and adult D. magna by inhibiting enzymes, an increase in lipid peroxidation levels and changes both transcription levels of enzymes (cat, gst). On the whole, juveniles and adults both responded similarly to DEHP. Our findings will contribute to the understanding of toxic mechanisms in phthalate esters and the evaluation of environmental risks in aquatic ecosystems.

Evolution of photoinduced effects in phase-separated Sm0.5Sr0.5Mn1-yCryO3 thin films.

Systematic study on electrical transport properties has been performed in Sm0.5Sr0.5Mn1-yCryO3 thin films illuminated by the light. An evolution of persistent and transient photoinduced effects induced by the impurity doping and temperature has been observed, which is closely related to the number of ferromagnetic clusters. The maximum persistent photoinduced effect is observed at y = 0.08 and the corresponding value is about 61.7% at the power density of 13.7 mW/mm(2). The underlying mechanism can be understood by the coexistence and competition of the multiphases in phase-separated manganites induced by Cr-doping. These results would pave the way for practical applications in innovative photoelectric devices of all-oxides.

The complete mitochondrial genome of Buccinum pemphigum (Neogastropoda: Buccinidae).

In this study, the complete mitogenome of Buccinum pemphigum has been determined. The complete mitochondrial genome is 15 265 bp in length, including 13 protein-coding genes, two rRNA genes and 22 tRNA genes. The total base composition is 30.1% A, 15.8% G, 15.1% C and 39.0%T, with a high AT content of 69.1%. Tree constructed using maximum-likelihood (ML) phylogenetic method, demonstrated that B. pemphigum has a close relationship to Volutharpa perryi clustered in Buccinoidea. First, this complete mitogenome of Buccinum will facilitate the development of new DNA markers for species identification.

[Reducing the maize amylopectin content through RNA interference manipulation].

To regulate the biosynthesis of maize starch, gene segment of starch branch enzyme (SBE) in maize was cloned and an expression vector of small interference RNA with the fragment of antisense gene + sense gene (pCJSBE2b, Fig.1) was constructed. The expression vector of pCJSBE2b was transformed into maize inbred lines by using pollen-tube pathway. Results of PCR amplification and Southern blotting indicated that the aimed gene with the fragment of antisense gene + sense gene had integrated into receptor maize genome (Fig.4,5) and inherited steadily in the transgenic plants (Table 1). Northern hybridization analysis showed that the aimed gene transcribed normally in the transgenic plants, which resulted in a reduction of endogenous SBE mRNA (Fig.6). The analysis of the activity of starch branching enzyme showed that the enzyme activity decreased obviously in the transgenic plants and maximum decrease was 85% compared to the control plants (Fig.7a). Although the total starch content of transgenic plants showed no change compared to the control plants but the amylose content increased to 50% (Fig.7b) in transgenic plants about 27% higher than receptor maize plants.