Self-assembly of an amino acid derivative as an anode interface layer for advanced alkaline Al-air batteries.

Alkaline Al-air batteries (AABs) are gaining increasing attention for large-scale energy storage systems due to their attractive intrinsic safety and cost-effectiveness. Nonetheless, the future development of AABs is substantially hampered by water-induced self-corrosion processes on the Al anode. In this work, we introduce an amino acid derivative, namely Nα-Boc-N1-formyl-L-tryptophan (NBLT), into a 4 M NaOH electrolyte to construct a unique layer that can effectively regulate the surface microstructure of the Al anode. The findings of the experiments show that NBLT can be used as a reliable corrosion inhibitor. The effectiveness of such inhibitors increases with NBLT concentration, reaching a maximum of 73.9% at 1.5 mM. In comparison to the pristine condition, there is a significant increase in anode utilization from 31.8% to 82.9%, capacity density from 947.9 to 2469.1 mA h g-1, and energy density from 1261.6 to 3384.6 W h kg-1. Theoretical calculations indicate that the carboxyl moieties present in the NBLT molecule establish coordination bonds with the Al atoms, thereby exerting a dominant role in the formation of the self-assembled barrier. The present investigation paves an effective strategy to inhibit reactions between anodes and electrolytes for advanced AABs.

Regulating the Anode Corrosion by a Tryptophan Derivative for Alkaline Al-Air Batteries.

Screening a green corrosion inhibitor that can prevent Al anode corrosion and enhance the battery performance is highly significant for developing next-generation Al-air batteries. This work explores the non-toxic, environmentally safe, and nitrogen-rich amino acid derivative, N(α)-Boc-l-tryptophan (BCTO), as a green corrosion inhibitor for Al anodes. Our results confirm that BCTO has an excellent corrosion inhibition effect for the Al-5052 alloy in 4 M NaOH solution. An optimum inhibitor addition (2 mM) has increased the Al-air battery performance; the corrosion inhibition efficiency was 68.2%, and the anode utilization efficiency reached 92.0%. The capacity and energy density values increased from 990.10 mA h g-1 and 1317.23 W h kg-1 of the uninhibited system to 2739.70 mA h g-1 and 3723.53 W h kg-1 for the 2 mM BCTO added system. The adsorption behavior of BCTO on the Al-5052 surface was further explored by theoretical calculations. This work paves the way for constructing durable Al-air batteries through an electrolyte regulation strategy.

Stability of oxygen vacancies at metal/oxide interfaces.

We investigated the influence of work function and charge doping on the formation of oxygen vacancies in metal/oxide heterojunctions by first-principles calculations. SrTiO3 is used as a typical oxide. Simple metals Pt, Au and Ag are used as electrodes. We show that electron doping could improve the formation energy of oxygen vacancies. In such a heterojunction, we found that the work function of the metal electrode affects the stability of oxygen vacancies in SrTiO3. For an electrode with a smaller work function, more electrons are induced and accumulated in the oxides near the interface and improve the formation energy of oxygen vacancies. We also studied the effect of ferroelectric polarization in a heterojunction of metal/BaTiO3 and found similar properties. We hope that our work could help in the design of complex-oxide-based electronic devices.

Effect of Indole-2-carboxylic Acid on the Self-Corrosion and Discharge Activity of Aluminum Alloy Anode in Alkaline Al-Air Battery.

Al-air battery has been regarded as a promising new energy source. However, the self-corrosion of aluminum anode leads to a loss of battery capacity and a decrease in battery longevity, limiting its commercial applications. Herein, indole-2-carboxylic acid (ICA) has been added to 4 M NaOH as a corrosion inhibitor. Its impact on the self-corrosion of aluminum alloy and the enhancement of the functionality of Al-air batteries at various concentrations have been investigated. X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques have been used to examine the compositional and morphological alterations of aluminum alloy surfaces. Electrochemical and hydrogen evolution tests showed that indole-2-carboxylic acid is an efficient corrosion inhibitor in alkaline solutions, and its impact grows with concentration. Our findings demonstrated that when the inhibitor concentration is 0.07 M, the inhibition efficiency is 54.0%, the anode utilization rises from 40.2% to 79.9%, the capacity density increases from 1197.6 to 2380.9 mAh g-1, and the energy density increases from 1469.9 to 2951.8 Wh kg-1. In addition, theoretical calculations have been performed to support the experimental results.

Two dimensional monolayers TetraHex-CX2 (X = N, P, As, and Sb) with superior electronic, mechanical and optical properties.

The discovery of graphene in 2004 opened a new world of two dimensional (2D) materials, stimulating the broad explorations of other novel 2D carbon structures and their derivatives in many materials fields. Although many 2D materials have been proposed theoretically, the experimental fabrication of them remains a big challenge, leading to more efforts to explore novel 2D materials with excellent properties. Here, we constructed four 2D monolayers TetraHex-CX2 (X = N, P, As, and Sb) using first-principles calculations. These thin materials composed of tetragonal and hexagonal rings exhibit good stabilities, extraordinarily flexible mechanical properties, indirect bandgaps (≤2.30 eV except TetraHex-CN2) with a semiconducting nature and a strong optical absorption up to 105 cm-1, showing the potential nanomechanical, nanoelectronic and optoelectronic applications. On building the structure-property relationship, we found that the Pauling electronegativity of X has an important influence on the electronic and mechanical properties of CX2, which provides a significant understanding of the fundamental origin of materials properties and is helpful to design novel 2D materials with special properties.

Leaf vein disease in Nelumbo nucifera caused by Nigrospora pyriformis infection in China.

Nelumbo nucifera (Nymphaeaceae) has both ornamental and nutritional uses in China. In July 2021, a novel disease was observed on plants in the White Lotus Science and Technology Expo Park in Guangchang county, Fuzhou city, Jiangxi province (26.79° N, 116.31° E). Infection was visible as nearly round black spots on the leaves in the early stages of infection. At later stages, the spots spread along the veins forming reticular necrosis until the entire leaf was infected, and the disease caused approximately 20% of leaves to die. To identify the pathogenic organism, 5×5 mm samples were taken from affected tissue adjoining healthy tissue, sterilized in 75% ethanol for 30 s, and immersed in 0.1% mercury chloride for a further 30 s, before washing in sterile water and transfer to potato glucose agar (PDA) plates. After culturing at 28℃±1℃ for five days, white regularly shaped round colonies were visible that after 10 days turned black with fluffy hyphae. The individual conidia produced by the conidiophore were initially a light-brown color which changed to black as the pigment accumulated; conidia were globose to subglobose, 17.10 (14.77-21.66) ×14.70 (12.08-16.93) µm in size (n=50), with glossy even surfaces lacking in septa, suggestive of Nigrospora. To verify this, PCR amplification was conducted using ITS1/ITS4 primers for the 5.8S rRNA gene. The primers EF1-728F and EF-2 were used for amplifying translation elongation factor 1α (O'Donnell et al. 1998, Carbone and Kohn 1999), and Bt-2a and Bt-2b (Glass and Donaldson 1995) for amplifying ß-tubulin. The sequences were found to be 99% to 100% identical to those of Nigrospora pyriformis in GenBank (accession numbers NR153469.1, KY019290.1, and KY019457.1, respectively). The sequences were uploaded to GenBank (accession numbers OK605048, OL362197, and OK662966), with lengths of 522 bp, 475 bp, and 410 bp, respectively. A maximum-likelihood phylogenetic tree was created in MEGA5. Pathogenicity was tested by four isolates hyphal inoculation and conducted in an experimental field of the White Lotus Science and Technology Expo Park. Five-millimeter discs were taken from infected and uninfected PDA plates and inoculated into five 1-month-old healthe lotus leaves using inoculations, three with the pathogen and an uninfected sample as the control every leaf. The discs were covered with moisturized sterile cotton and fixed with transparent tape. The wounds were moistened with sterile water and sealed with adhesive tape. After 14 days, spots were visible at the infected sites while the control sites showed no symptoms. The same pathogen was recovered from the infected leaves, fulfilling Koch's requirements. Leaf spot diseases resulting from N. pyriformis infection or infection with other Nigrospora species include infection of Chenopodium album by N. pyriformis (Chen et al. 2020), Eclipta prostrata by N. sphaerica (Qiu et al. 2022), Nicotiana tabacum by N. oryzae (Wang et al. 2022), and Oxalis corymbosa by N. hainanensis (Zheng et al. 2021). This investigation appears to be the first identification of Nelumbo nucifera vein disease resulting from Nigrospora pyriformis infection. The present results are useful for the management and avoidance of the disease caused by Nigrospora pyriformis.

First report of spotting disease caused by Fusarium proliferatum infection of Alisma orientale in China.

Alisma orientale (Alismatidae) is highly valued for both its pharmaceutical and nutritional properties. The tubers are in Chinese herbal medicine and the leaves and stems for several Chinese delicacies. Intercropping A. orientale and Nelumbo nucifera may increase quality, yield, and other economic benefits. In July 2021, a novel spotting disease was observed in these plants in the White Lotus Science and Technology Expo Park in Guangchang County, Fuzhou City, Jiangxi Province (26.79°N, 116.31°E). The symptom was round to regular black spots on the stems during the early stage of infection. Over time, the larger spots merged, resulting in stem breakage and eventually death. A. orientale spot disease arose in July of 2021, causing approximately 50% of leaves to die, and leading to 10 to 25% yield loss. To identify the pathogenic organism, 5×5 mm samples were taken from affected tissue adjoining healthy tissue, sterilized in 75% ethanol for 30 s, and immersed in 0.1% mercury chloride for a further 30 s, before washing in sterile water and transfer to potato glucose agar (PDA) plates. After culturing at 28℃±1℃ for seven days, aerial mycelia were identified. At the start of culture, the mycelia were white but later turned purple-red. Three to five straight or partially bent septa were visible on the macroconidia, which were 28.8(19.1~38.6) ×2.9(1.9~4.0) µm in size (n=50). In contrast, the microconidia appeared glassy and elliptical, with sizes of 9.8(4.9~14.8) ×2.7(1.2~4.1) µm (n=50). These features suggested F. proliferatum (Zhao et al., 2019). To verify this, various primers, including universal ITS1/ITS4, Fusarium-specific EF1T/EF2T, PRO1/PRO2 (Mulè et al., 2004), and Bt2a/Bt2b (Glass and Donaldson, 1995; O'Donnell and Cigelnik, 1998) primers were used for amplification of the 5.8S rRNA/ITS, α-elongation factor, calmodulin, and ß-tubulin genes. The resulting sequences were between 99% and 100% identical to those of F. proliferatum in GenBank (accession numbers MW721116.1, KR071735.1, KU604008.1, and MH398186.1, respectively). The present sequences were uploaded with accession numbers of OK047496, OL448294, OL448295, and OM280358, with sequence lengths of 549 bp, 725 bp, 594 bp, and 325bp, respectively. A maximum likelihood-phylogenetic tree was created in MEGA5 based on ITS+TEF+PRO sequences. Pathogenicity was tested by hyphal inoculation. Needles, cotton, and water were sterilized under high temperature and pressure. Five-millimeter punches were taken from infected and uninfected PDA plates and three uninfected stems of A. orientale were inoculated with the pathogen with a fourth used as the control. Plants were maintained in experimental field of the Bailian Science and Technology Expo Park. Infected wounds were gently wetted with sterile water and sealed with sellotape. After 10 days, the infected stems displayed symptoms while the controls did not. The same pathogen was recovered from the infected stems, fulfilling Koch's requirements. This appears to be the only report describing F. proliferatum infection of A. orientale stems. These results are useful for the recognition and avoidance of F. proliferatum infections in A. orientale and other plants.

First report of Alternaria alternata causing leaf spot on Nelumbo nucifera plants in China.

White lotus (Nelumbo nucifera) is an aquatic plant of the Nymphaeaceae family that primarily serves as an ornamental plant and is an important cash crop in China. In May 2020, an unknown leaf disease affecting these plants was first detected in White Lotus Science and Technology Expo Park in Guangchang County, Fuzhou City, Jiangxi Province (26.79° N, 116.31° E). The disease caused approximately 30-40% of leaves to die, and led to 15 to 20% in seed yield losses. This disease was characterized by the formation of irregular yellow-brown to dark-brown spots during the initial phases of infection. As the disease is developing, these spots expanded until they were generally round and brown to purple-brown in color, with a yellow halo surrounding the expanding spots. In an effort to characterize the causative pathogen, a small ~5×5 mm leaf tissue section from the boundary between normal and diseased tissue was collected, and sterilized with the following regimes: 30 s with 75% ethanol, soaked in 0.1% mercuric chloride for 30 s, washed thrice with sterile water, and transferred onto potato dextrose agar (PDA) plate, and placed in an illumination incubator (12 h light/dark) at 28 °C± 1°C for 5 days. Seven pure cultures were obtained from ten diseased leaves. For pathogenicity testing, a hyphal inoculation strategy was employed, with all studies being conducted at the Plant Pathology Laboratory of Jiangxi Agricultural University. Five mm discs were selected from three separate cultures and one control (PDA). Healthy leaves of lotus seeds were treated with 4 treatments per leaf including three separate cultures and one control that were treated with the test pathogen. The experiments were repeated three times with three biological replicates. Healthy leaves were covered with moisturized sterile cotton balls and fixed to the leaf surface with transparent tape. The inoculated lotus seedlings were kept in greenhouse incubator at 28 °C± 3°C and relative humidity of 70 to 80%. Following a 14-day incubation period, brown spots began to manifest at all sites inoculated with the test pathogen whereas the control spots remained healthy. Diseased spots were then separated. The same pathogen was once again successfully isolated and identified microscopically, thus fulfilling Koch's postulates. Six isolates were characterized. Ovoid or elliptical conidia were brown to light-brown in color with a short beak, 1-5 diaphragms, and 0-3 mediastinum. The diameter of these conidia were thick (13.8-44.0×7.5-16.3 µm; average: 24.0×11.9 µm, n=50). These morphological characteristics were consistent with Alternaria alternata. The ITS4/ITS5, EF1-728F/EF1-986R, AltF/AltR, OPA10-2R/OPA10-2L, EPGF/EPGR and KOG1058F2/KOG1058R2 primer sets were then used to conduct molecular identification by amplifying key transcription elongation factor and internal transcriptional spacer regions, yielding sequences that were 99%-100% similar to Alternaria alternata (GenBank No: MK396606, MT178329, MN184998, MN894688, MT849815 and KP125234). Sequences were deposited in GenBank with accession numbers MW898580 (ITS, 620 bp), MW981281 (EF1-α, 284 bp), MZ514094 (Alt a1, 477 bp), MZ514095 (OPA10-2, 716 bp), MZ514096 (endoPG, 465 bp) and MZ514097 (KOG1058, 877 bp). Nelumbo nucifera is an important aquatic cash crop in China, and this is the first study we are aware of demonstrating the presence of a leaf disease caused by Alternaria alternata in Nelumbo nucifera plants anywhere in the world. These findings may offer a foundation for efforts to prevent diseases caused by Alternaria alternata.

Transcriptome Analyses Revealed the Key Metabolic Genes and Transcription Factors Involved in Terpenoid Biosynthesis in Sacred Lotus.

As the largest group of structurally diverse metabolites, terpenoids are versatile natural compounds that act as metabolism mediators, plant volatiles, and ecological communicators. However, few terpenoid compounds have been identified in plant parts of sacred lotus (Nelumbo nucifera Gaertn.). To elucidate the molecular genetic basis of the terpene biosynthetic pathway, terpenes from different parts of the plant, including seeds (S), young leaves (YL), mature leaves (ML), white flowers (WF), yellow flowers (YF), and red flowers (RF), were identified by LC-MS/MS and the relative contents of the same terpenes in different parts were compared. The results indicate that all plant parts primarily consist of triterpenes, with only minor quantities of sesquiterpenes and diterpenes, and there were differences in the terpene content detected in different plant parts. To illustrate the biosynthesis of various terpenoids, RNA sequencing was performed to profile the transcriptomes of various plant parts, which generated a total of 126.95 GB clean data and assembled into 29,630 unigenes. Among these unigenes, 105 candidate unigenes are involved in the mevalonate (MVA) pathway, methyl-erythritol phosphate (MEP) pathway, terpenoid backbone biosynthesis pathway, and terpenoid synthases pathway. Moreover, the co-expression network between terpene synthase (TPS) and WRKY transcription factors provides new information for the terpene biosynthesis pathway.

Bioinspired PDMS-graphene cantilever flow sensors using 3D printing and replica moulding.

Flow sensors found in animals often feature soft and slender structures (e.g. fish neuromasts, insect hairs, mammalian stereociliary bundles, etc) that bend in response to the slightest flow disturbances in their surroundings and heighten the animal's vigilance with respect to prey and/or predators. However, fabrication of bioinspired flow sensors that mimic the material properties (e.g. low elastic modulus) and geometries (e.g. high-aspect ratio (HAR) structures) of their biological counterparts remains a challenge. In this work, we develop a facile and low-cost method of fabricating HAR cantilever flow sensors inspired by the mechanotransductory flow sensing principles found in nature. The proposed workflow entails high-resolution 3D printing to fabricate the master mould, replica moulding to create HAR polydimethylsiloxane (PDMS) cantilevers (thickness = 0.5-1 mm, width = 3 mm, aspect ratio = 20) with microfluidic channel (150 µm wide × 90 µm deep) imprints, and finally graphene nanoplatelet ink drop-casting into the microfluidic channels to create a piezoresistive strain gauge near the cantilever's fixed end. The piezoresistive flow sensors were tested in controlled airflow (0-9 m s-1) inside a wind tunnel where they displayed high sensitivities of up to 5.8 kΩ m s-1, low hysteresis (11% of full-scale deflection), and good repeatability. The sensor output showed a second order dependence on airflow velocity and agreed well with analytical and finite element model predictions. Further, the sensor was also excited inside a water tank using an oscillating dipole where it was able to sense oscillatory flow velocities as low as 16-30 µm s-1 at an excitation frequency of 15 Hz. The methods presented in this work can enable facile and rapid prototyping of flexible HAR structures that can find applications as functional biomimetic flow sensors and/or physical models which can be used to explain biological phenomena.

First Report of Lotus Seedpod Withering Caused by Fusarium proliferatum on Nelumbo nucifera Plants in China.

Nelumbo nucifera (Nymphaeaceae family) is a well-known plant in China and with the increasing value of this crop, the planting area of lotus is expanding. In May 2019, an unknown withering lotus seedpod was obtained in Guangchang County of Jiangxi Province (26.79°N, 116.31°E). The disease arose between May and July of each year, resulted in the withering and consequent death of ~10% of lotus seedpods, with the disease being most serious during the rainy season. The initial symptoms of this disease include the shrinking of young lotus seedpods with concomitant yellowing of the epidermal tissue layer. These pods failed to grow normally and could to wither and die within one week, with the withering symptoms gradually spreading to associated stem tissues. To characterize the pathogens responsible for this disease, ten diseases seedpods were collected and cut into pieces of ~5×5 mm, then sterilized with 75% ethanol for 30 s, and treated with 0.1% mercuric chloride for 5 min. After being washed four times under sterilized water, samples were then transferred onto potato dextrose agar (PDA) and incubated for 7 d at 28℃ in the dark. Eight purified isolates yielded large numbers of aerial mycelium that were initially white in color, but then changed to a purple-red color over the course of this incubation period. The average mycelial growth rate was 6.3 mm per day (n=5). On PDA, macroconidia exhibited 3-5 septa and were straight or slightly curved, with a size of 21.6-47.4×2.5-4.6 µm (average: 31.9×3.5 µm, n=50). The microconidia were hyaline, ovoid or ellipse and 4.6-13.5×2.2-4.3 µm in size (average: 8.7×3.1 µm, n=50). The morphological features of these fungi were noted to be in line with those of Fusarium proliferatum (Leslie and Summerell, 2006; Zhao et al., 2019). To confirm the identity of this putative pathogen at the molecular level, the universal ITS4/ITS5 primers (White et al., 1990), the Fusarium specific pair PRO1/PRO2 (Mulè et al., 2004), EF1T/EF2T (O'Donnell et a., 1998) and RPB2F/R (O'Donnell et al., 2010) primers were utilized to amplify the internal transcribed spacer 1 (ITS1)-5.8S rRNA gene-internal transcribed spacer 2 (ITS2), calmodulin, alpha elongation factor genes, and RNA-dependent DNA polymerase II subunit from these isolates. Following alignment of the resultant sequences with GenBank via a BLAST analysis, the sequences (GenBank accession numbers: MW862499, MW762531, MW767988, MW831311, respectively.) showed 100% identities to the corresponding DNA sequences in F. proliferatum (GenBank accession numbers: MW817705, LS423443, MH153750, and MW091308, respectively.). Based upon these morphological and molecular findings, this pathogen was identified as F. proliferatum. Pathogenicity testing was then performed using five plump healthy lotus seedpods. Sterile needles were used to generate wounds (2 mm deep, 1 mm in diameter) a 10 µL suspension of prepared spores (1.0×106 spores/mL) derived from a 7-day-old culture grown on PDA was injected into the wound sites of the lotus seedpod. As a control, give seedpods were additionally wounded and injected as the same as treated with 10 µL of sterile water. The experiments were repeated three times with five biological replicates. All seedpods were then incubated at 28℃ in a growth chamber (12 h light/dark) with 80% relative humidity. After a 3-day incubation period, wounded sites injected with spore suspensions exhibited browning. Following a 5-day incubation period, a mean lesion diameter of 9.8 mm was observed, with white mycelia growing on the wound surface and with evident withering of the internal and external tissues near the wounded site. In contrast, blank control wound sites remained healthy. We were again able to isolate F. proliferatum from the infected lotus seedpods. Finally, eight isolates were obtained were identified as the pathogen based on these morphological and molecular analyses, thus fulfilling Koch's postulates. This is the first report to our knowledge to have described a case of F. proliferatum causing lotus seedpod withering in China, providing a foundation for future research efforts aimed at presenting diseases caused by this pathogen.

Comparative population genomics reveals genetic divergence and selection in lotus, Nelumbo nucifera.

BACKGROUND: Lotus (Nelumbo nucifera) is an aquatic plant with important agronomic, horticulture, art and religion values. It was the basal eudicot species occupying a critical phylogenetic position in flowering plants. After the domestication for thousands of years, lotus has differentiated into three cultivated types -flower lotus, seed lotus and rhizome lotus. Although the phenotypic and genetic differentiations based on molecular markers have been reported, the variation on whole-genome level among the different lotus types is still ambiguous. RESULTS: In order to reveal the evolution and domestication characteristics of lotus, a total of 69 lotus accessions were selected, including 45 cultivated accessions, 22 wild sacred lotus accessions, and 2 wild American lotus accessions. With Illumina technology, the genomes of these lotus accessions were resequenced to > 13× raw data coverage. On the basis of these genomic data, 25 million single-nucleotide polymorphisms (SNPs) were identified in lotus. Population analysis showed that the rhizome and seed lotus were monophyletic and genetically homogeneous, whereas the flower lotus was biphyletic and genetically heterogeneous. Using population SNP data, we identified 1214 selected regions in seed lotus, 95 in rhizome lotus, and 37 in flower lotus. Some of the genes in these regions contributed to the essential domestication traits of lotus. The selected genes of seed lotus mainly affected lotus seed weight, size and nutritional quality. While the selected genes were responsible for insect resistance, antibacterial immunity and freezing and heat stress resistance in flower lotus, and improved the size of rhizome in rhizome lotus, respectively. CONCLUSIONS: The genome differentiation and a set of domestication genes were identified from three types of cultivated lotus- flower lotus, seed lotus and rhizome lotus, respectively. Among cultivated lotus, flower lotus showed the greatest variation. The domestication genes may show agronomic importance via enhancing insect resistance, improving seed weight and size, or regulating lotus rhizome size. The domestication history of lotus enhances our knowledge of perennial aquatic crop evolution, and the obtained dataset provides a basis for future genomics-enabled breeding.

Catalytic Enantioselective Intramolecular C(sp3 )-H Amination of 2-Azidoacetamides.

An enantioselective ring-closing C(sp3 )-H amination of 2-azidoacetamides is catalyzed by a chiral-at-metal ruthenium complex and provides chiral imidazolidin-4-ones in 31-95 % yield, with enantioselectivities of up to 95 % ee, and at catalyst loadings down to 0.1 mol % (turnover number (TON)=740). To our knowledge, this is the first example of a highly enantioselective C(sp3 )-H amination with aliphatic azides. Mechanistic experiments reveal the importance of the amide group, which presumably enables initial bidentate coordination of the 2-azidoacetamides to the catalyst. DFT calculations show that the transition state leading to the major enantiomer features a better steric fit and favorable π-π stacking between the substrate and the catalyst framework.

Evaluation and validation of suitable reference genes for quantitative real-time PCR analysis in lotus (Nelumbo nucifera Gaertn.).

The qRT-PCR technique has been regarded as an important tool for assessing gene expression diversity. Selection of appropriate reference genes is essential for validating deviation and obtaining reliable and accurate results. Lotus (Nelumbo nucifera Gaertn) is a common aquatic plant with important aesthetic, commercial, and cultural values. Twelve candidate genes, which are typically used as reference genes for qRT-PCR in other plants, were selected for this study. These candidate reference genes were cloned with, specific primers designed based on published sequences. In particular, the expression level of each gene was examined in different tissues and growth stages of Lotus. Notably, the expression stability of these candidate genes was assessed using the software programs geNorm and NormFinder. As a result, the most efficient reference genes for rootstock expansion were TBP and UBQ. In addition, TBP and EF-1α were the most efficient reference genes in various floral tissues, while ACT and GAPDH were the most stable genes at all developmental stages of the seed. CYP and GAPDH were the best reference genes at different stages of leaf development, but TUA was the least stable. Meanwhile, the gene expression profile of NnEXPA was analyzed to confirm the validity of the findings. It was concluded that, TBP and GAPDH were identified as the best reference genes. The results of this study may help researchers to select appropriate reference genes and thus obtain credible results for further quantitative RT-qPCR gene expression analyses in Lotus.

Undulating Seal Whiskers Evolved Optimal Wavelength-to-Diameter Ratio for Efficient Reduction in Vortex-Induced Vibrations.

Seals are well-known for their remarkable hydrodynamic trail-following capabilities made possible by undulating flow-sensing whiskers that enable the seals to detect fish swimming as far as 180 m away. In this work, the form-function relationship in the undulating whiskers of two different phocid seal species, viz. harbor and gray seals, is studied. The geometry and material properties of excised harbor and grey seal whiskers are systematically characterized using blue light 3D scanning, optical and scanning electron microscopy, and nanoindentation. The effect of the undulating geometry on the whiskers' vibration in uniform water flow is studied using both experimental (piezoelectric MEMS and 3D-printed piezoresistive sensors developed in-house) and numerical (finite element method) techniques. The results indicate that the dimensionless ratio of undulation wavelength to mean whisker diameter (λ/Dm ) in phocid seals may have evolved to be in the optimal range of 4.4-4.6, enabling an order-of-magnitude reduction in vortex-induced vibrations (compared to a similarly-shaped circular cylinder) and, consequently, an enhanced flow sensing capability with minimal self-induced noise. The results highlight the importance of the dimensionless λ/Dm ratio in the biomimetic design of seal whisker-inspired vibration-resistant structures, such as marine risers and wake detection sensors for submarines.

Wavy Whiskers in Wakes: Explaining the Trail-Tracking Capabilities of Whisker Arrays on Seal Muzzles.

Seals can detect prey up to 180 m away using only their flow-sensing whiskers. The unique undulating morphology of Phocid seal whiskers reduces vortex-induced vibrations (VIVs), rendering seals highly sensitive to biologically relevant flow stimuli. In this work, digital models of harbor and grey seal whiskers are extracted using 3D scanning and a mathematical framework that accurately recreates their undulating geometry is proposed. Through fluid-structure interaction studies and experimental investigations involving a whisker array mounted on 3D-printed microelectromechanical systems sensors, the vibration characteristics of the whisker array and the interaction between neighboring whiskers in steady flows and fish-wake-like vortices are explained for the first time. Results reveal that the downstream vortices intensity and resulting VIVs are consistently lower for grey than harbor seal whiskers and a smooth cylinder, suggesting that the grey seal whisker geometry can be an ideal template for the biomimetic design of VIV-resistant underwater structures. In addition, neighboring whiskers in an array influence one another by resulting in greater flow vorticity fluctuation and distribution area, thus causing increased vibrations than an isolated whisker, which indicates the possibility of a signal-strengthening effect in whisker arrays.

Optimized Anticorrosion of Polypyrrole Coating by Inverted-Electrode Strategy: Experimental and Molecular Dynamics Investigations.

To improve the poor adhesion and the ensuing insufficient anticorrosion efficacy of electropolymerized polypyrrole (PPy) on copper surface, an inverted-electrode strategy was applied after the passivation procedure, for which the compact coating (PPy-I) was deposited on the substrate in a cathodic window. Morphological and physical characterizations revealed that PPy-I exerted satisfactory adhesion strength and suitable thickness and conductivity compared with the analogue prepared via the traditional protocol (PPy-T). Potentiodynamic polarization, electrochemical impedance spectroscopy and frequency modulation were employed to ascertain the propitious protection of PPy-I for copper in artificial seawater (ASW). Due to the dominant electroactivity, the PPy-I-coated sample possessed higher apparent current density and lower charge transfer resistance than its PPy-T-protected counterpart, which maintained the passivation of the substrate. Surface analysis also supported the viability of PPy-I for copper in ASW for a well-protected surface with inferior water wettability. Molecular dynamics simulations evidenced that PPy-I with the higher density retained efficient anticorrosion capacity on copper at elevated temperatures. Therein, the derived time-dependent spatial diffusion trajectories of ions were locally confined with low diffusion coefficients. Highly twisted pore passages and anodic protection behavior arising respectively from the tight coating architecture and electroactivity contributed to the adequate corrosion resistance of PPy-I-coated copper.

Differential expression involved in starch synthesis pathway genes reveal various starch characteristics of seed and rhizome in lotus (Nelumbo Nucifera).

Lotus (Nelumbo nucifera) is one of the main aquatic vegetables in China. Its seed and rhizome are main edible parts which are rich in starch. Preliminary experiments of starch contents revealed that seed and rhizome expressed great differences in amylose and amylopectin contents. The rhizomes have higher amylopectin content, while the seeds have higher amylose content. In this study, we have estimated 16 varieties of lotus seeds and found that the amylose content of lotus seeds ranged from 30% to 50%, with an average amylose content of 43%, which showed high-amylose content characteristics. Morphological analysis of lotus seed shown that starch rapid accumulated in 20 DAF (day after fertilization) ∼ 26 DAF. Transcriptome of lotus seeds indicated that starch genes played an important role in seed development. Especially in 22 DAF, the genes which controlled amylose synthesis significantly increased, in contrast, the expression of amylopectin-related genes was stable and might limit the synthesis of amylopectin. We further analyzed the expression patterns of 11 key related genes between lotus seeds and rhizomes, and found that the expression of amylose-related genes to were higher in lotus seed, while the expression of genes related to amylopectin synthesis were higher in rhizome. This study provided a comprehensive research of molecular basis for starch in lotus seed and rhizome. Different expression among key genes during starch accumulation might be the principal cause of the differences in starch properties between seed and rhizome. PRACTICAL APPLICATION: Differential expression involved in starch synthesis pathway genes is the main reason for various starch characteristics of seed and rhizome in lotus. High amylose content in lotus seed is a valuable trait for developing functional food.

Underwater robot coordination using a bio-inspired electrocommunication system.

Due to the challenging communication and control systems, few underwater multi-robot coordination systems are currently developed. In nature, weakly electric fish can organize their collective activities using electrocommunication in turbid water. Inspired by this communication mechanism, we developed an artificial electrocommunication system for underwater robots in our previous work. In this study, we coordinate a group of underwater robots using this bio-inspired electrocommunication. We first design a time division multiple access (TDMA) network protocol for electrocommunication to avoid communication conflicts during multi-robot coordination. Then, we revise a distributed controller to coordinate a group of underwater robots. The distributed controller on each robot generates the required controls based on adjacent states obtained through electrocommunication. A central pattern generator (CPG) controller is designed to adjust the speed of individuals according to distributed control law. Simulations and experimental results show that a group of underwater robots is able to achieve coordination with the developed electrocommunication and control systems.

Glowing Sucker Octopus (Stauroteuthis syrtensis)-Inspired Soft Robotic Gripper for Underwater Self-Adaptive Grasping and Sensing.

A soft gripper inspired by the glowing sucker octopus (Stauroteuthis syrtensis)' highly evolved grasping capability enabled by the umbrella-shaped dorsal and ventral membrane between each arm is presented here, comprising of a 3D-printed linkage mechanism used to actuate a modular mold silicone-casting soft suction disc to deform. The soft gripper grasp can lift objects using the suction generated by the pump in the soft disc. Moreover, the protruded funnel-shaped end of the deformed suctorial mouth can adapt to smooth and rough surfaces. Furthermore, when the gripper contacts the submerged target objects in a turbid environment, local suctorial mouth arrays on the suction disc are locked, causing the variable flow inside them, which can be detected as a tactile perception signal to the target objects instead of visual perception. Aided by the 3D-printed linkage mechanism, the soft gripper can grasp objects of different shapes and dimensions, including flat objects, objects beyond the grasping range, irregular objects, scattered objects, and a moving turtle. The results report the soft gripper's versatility and demonstrate the vast application potentials of self-adaptive grasping and sensing in various environments, including but are not limited to underwater, which is always a key challenge of grasping technology.