Centimeter-sized diamond composites with high electrical conductivity and hardness.

Achieving high-performance materials with superior mechanical properties and electrical conductivity, especially in large-sized bulk forms, has always been the goal. However, it remains a grand challenge due to the inherent trade-off between these properties. Herein, by employing nanodiamonds as precursors, centimeter-sized diamond/graphene composites were synthesized under moderate pressure and temperature conditions (12 GPa and 1,300 to 1,500 °C), and the composites consisted of ultrafine diamond grains and few-layer graphene domains interconnected through covalently bonded interfaces. The composites exhibit a remarkable electrical conductivity of 2.0 × 104 S m-1 at room temperature, a Vickers hardness of up to ~55.8 GPa, and a toughness of 10.8 to 19.8 MPa m1/2. Theoretical calculations indicate that the transformation energy barrier for the graphitization of diamond surface is lower than that for diamond growth directly from conventional sp2 carbon materials, allowing the synthesis of such diamond composites under mild conditions. The above results pave the way for realizing large-sized diamond-based materials with ultrahigh electrical conductivity and superior mechanical properties simultaneously under moderate synthesis conditions, which will facilitate their large-scale applications in a variety of fields.

Composition-dependent ordering transformations in Pt-Fe nanoalloys.

SignificanceDynamically understanding the microscopic processes governing ordering transformations has rarely been attained. The situation becomes even more challenging for nanoscale alloys, where the significantly increased surface-area-to-volume ratio not only opens up a variety of additional freedoms to initiate an ordering transformation but also allows for kinetic interplay between the surface and bulk due to their close proximity. We provide direct evidence of the microscopic processes controlling the ordering transformation through the surface-bulk interplay in Pt-Fe nanoalloys and new features rendered by variations in alloy composition and chemical stimuli. These results provide a mechanistic detail of ordering transformation phenomena which are widely relevant to nanoalloys as chemical ordering occurs in most multicomponent materials under suitable environmental bias.

A chromosome level genome assembly of Pseudoroegneria Libanotica reveals a key Kcs gene involves in the cuticular wax elongation for drought resistance.

BACKGROUND: The genus Pseudoroegneria (Nevski) Löve (Triticeae, Poaceae), whose genome symbol was designed as "St", accounts for more than 60% of perennial Triticeae species. The diploid species Psudoroegneria libanotica (2n = 14) contains the most ancient St genome, exhibited strong drought resistance, and was morphologically covered by cuticular wax on the aerial part. Therefore, the St-genome sequencing data could provide fundamental information for studies of genome evolution and reveal its mechanisms of cuticular wax and drought resistance. RESULTS: In this study, we reported the chromosome-level genome assembly for the St genome of Pse. libanotica, with a total size of 2.99 Gb. 46,369 protein-coding genes annotated and 71.62% was repeat sequences. Comparative analyses revealed that the genus Pseudoroegneria diverged during the middle and late Miocene. During this period, unique genes, gene family expansion, and contraction in Pse. libanotica were enriched in biotic and abiotic stresses, such as fatty acid biosynthesis which may greatly contribute to its drought adaption. Furthermore, we investigated genes associated with the cuticular wax formation and water deficit and found a new Kcs gene evm.TU.CTG175.54. It plays a critical role in the very long chain fatty acid (VLCFA) elongation from C18 to C26 in Pse. libanotica. The function needs more evidence to be verified. CONCLUSIONS: We sequenced and assembled the St genome in Triticeae and discovered a new KCS gene that plays a role in wax extension to cope with drought. Our study lays a foundation for the genome diversification of Triticeae species and deciphers cuticular wax formation genes involved in drought resistance.

Genome-wide development of simple sequence repeats markers and genetic diversity analysis of chayote.

BACKGROUND: Chayote is a high economic crop in the Cucurbitaceae family, playing an important role in food production, disease treatment and the production of degradable materials in industries. Due to the harsh environment, such as high temperature, drought and frost, some chayote resources are gradually disappearing. It is crucial to collect, characterize, and conserve chayote resources. However, the genetic diversity of chayote resources in China has not been studied so far. RESULTS: In this study, we collected 35 individuals of chayote from 14 provinces in China. Subsequently, we found 363,156 SSR motifs from the chayote genome and designed 57 pairs of SSR primers for validation. Out of these, 48 primer pairs successfully amplified bands, with 42 of them showing polymorphism. These 42 primer pairs detected a total of 153 alleles, averaging 3.64 alleles per locus. The polymorphic information content ranged from 0.03 to 0.78, with an average value of 0.41, indicating a high level of polymorphism. Based on the analysis using STRUCTURE, PCoA, and UPGMA methods, the 35 chayote individuals were divided into two major clusters. Through further association analysis, 7 significantly associated SSR markers were identified, including four related to peel color and three related to spine. CONCLUSIONS: These molecular markers will contribute to the analysis of genetic diversity and genetic breeding improvement of chayote in the future.

Operando characterization of conductive filaments during resistive switching in Mott VO2.

Vanadium dioxide (VO2) has attracted much attention owing to its metal-insulator transition near room temperature and the ability to induce volatile resistive switching, a key feature for developing novel hardware for neuromorphic computing. Despite this interest, the mechanisms for nonvolatile switching functioning as synapse in this oxide remain not understood. In this work, we use in situ transmission electron microscopy, electrical transport measurements, and numerical simulations on Au/VO2/Ge vertical devices to study the electroforming process. We have observed the formation of V5O9 conductive filaments with a pronounced metal-insulator transition and that vacancy diffusion can erase the filament, allowing for the system to "forget." Thus, both volatile and nonvolatile switching can be achieved in VO2, useful to emulate neuronal and synaptic behaviors, respectively. Our systematic operando study of the filament provides a more comprehensive understanding of resistive switching, key in the development of resistive switching-based neuromorphic computing.

Inherent stochasticity during insulator-metal transition in VO2.

Vanadium dioxide (VO2), which exhibits a near-room-temperature insulator-metal transition, has great potential in applications of neuromorphic computing devices. Although its volatile switching property, which could emulate neuron spiking, has been studied widely, nanoscale studies of the structural stochasticity across the phase transition are still lacking. In this study, using in situ transmission electron microscopy and ex situ resistive switching measurement, we successfully characterized the structural phase transition between monoclinic and rutile VO2 at local areas in planar VO2/TiO2 device configuration under external biasing. After each resistive switching, different VO2 monoclinic crystal orientations are observed, forming different equilibrium states. We have evaluated a statistical cycle-to-cycle variation, demonstrated a stochastic nature of the volatile resistive switching, and presented an approach to study in-plane structural anisotropy. Our microscopic studies move a big step forward toward understanding the volatile switching mechanisms and the related applications of VO2 as the key material of neuromorphic computing.

Physiological, anatomical and quality indexes of root tuber formation and development in chayote (Sechium edule).

BACKGROUND: Chayote is an underutilized species of Cucurbitaceae. It is rich in nutrients such as protein, minerals, phenols and its extracts have anti-cardiovascular and anti-cancer effects, making it a versatile plant for both medicinal and culinary purposes. Although research on its root tuber is limited, they are rich in starch and have a structure similar to that of potatoes, cassava, and sweet potatoes. Therefore, they can serve as potential substitutes for potatoes and offer promising prospects as agricultural and industrial resources. However, the physiological and cellular mechanisms of chayote root tuber formation and development are still unclear. RESULTS: In this study, we observed the growth habit of 'Tuershao' (high yield of root tuber). The results revealed that the tuber enlargement period of 'Tuershao' lasts approximately 120 days, with the early enlargement phase occurring during 0-30 days, rapid enlargement phase during 30-90 days, and maturation phase during 90-120 days. Physiological indicators demonstrated a gradual increase in starch content as the tuber developed. The activities of sucrose synthase (SUS) and invertase (VIN) showed a consistent trend, reaching the highest level in the rapid expansion period, which was the key enzyme affecting tuber expansion. Moreover, the special petal like structure formed by the secondary phloem and secondary xylem of the tuber resulted in its enlargement, facilitating the accumulation of abundant starch within the thin-walled cells of this structure. Principal component analysis further confirmed that starch content, SUS and VIN activities, as well as the concentrations of calcium (Ca), iron (Fe), and selenium (Se), were the major factors influencing tuber development. Moreover, the low temperature environment not only promoted the growth of 'Tuershao' tubers but also enhanced the accumulation of nutritional substances. CONCLUSIONS: These findings contribute to a deeper understanding of the formation and developmental mechanisms of 'Tuershao' tubers, providing valuable guidance for cultivation practices aimed at improving crop yield.

Superconductivity found in meteorites.

Meteorites can contain a wide range of material phases due to the extreme environments found in space and are ideal candidates to search for natural superconductivity. However, meteorites are chemically inhomogeneous, and superconducting phases in them could potentially be minute, rendering detection of these phases difficult. To alleviate this difficulty, we have studied meteorite samples with the ultrasensitive magnetic field modulated microwave spectroscopy (MFMMS) technique [J. G. Ramírez, A. C. Basaran, J. de la Venta, J. Pereiro, I. K. Schuller, Rep. Prog. Phys. 77, 093902 (2014)]. Here, we report the identification of superconducting phases in two meteorites, Mundrabilla, a group IAB iron meteorite [R. Wilson, A. Cooney, Nature 213, 274-275 (1967)] and GRA 95205, a ureilite [J. N. Grossman, Meteorit. Planet. Sci. 33, A221-A239 (1998)]. MFMMS measurements detected superconducting transitions in samples from each, above 5 K. By subdividing and remeasuring individual samples, grains containing the largest superconducting fraction were isolated. The superconducting grains were then characterized with a series of complementary techniques, including vibrating-sample magnetometry (VSM), energy-dispersive X-ray spectroscopy (EDX), and numerical methods. These measurements and analysis identified the likely phases as alloys of lead, indium, and tin.

Highly efficient binary copper-iron catalyst for photoelectrochemical carbon dioxide reduction toward methane.

A rational design of an electrocatalyst presents a promising avenue for solar fuels synthesis from carbon dioxide (CO2) fixation but is extremely challenging. Herein, we use density functional theory calculations to study an inexpensive binary copper-iron catalyst for photoelectrochemical CO2 reduction toward methane. The calculations of reaction energetics suggest that Cu and Fe in the binary system can work in synergy to significantly deform the linear configuration of CO2 and reduce the high energy barrier by stabilizing the reaction intermediates, thus spontaneously favoring CO2 activation and conversion for methane synthesis. Experimentally, the designed CuFe catalyst exhibits a high current density of -38.3 mA⋅cm-2 using industry-ready silicon photoelectrodes with an impressive methane Faradaic efficiency of up to 51%, leading to a distinct turnover frequency of 2,176 h-1 under air mass 1.5 global (AM 1.5G) one-sun illumination.

Genome-Wide Identification of the MADS-Box Gene Family during Male and Female Flower Development in Chayote (Sechium edule).

The MADS-box gene plays an important role in plant growth and development. As an important vegetable of Cucurbitaceae, chayote has great edible and medicinal value. So far, there is little molecular research on chayote, and there are no reports on the MADS-box transcription factor of chayote. In this study, the MADS-box gene family of chayote was analyzed for the first time, and a total of 70 MADS-box genes were identified, including 14 type I and 56 type II MICK MADS genes. They were randomly distributed on 13 chromosomes except for chromosome 11. The light response element, hormone response element and abiotic stress response element were found in the promoter region of 70 MADS genes, indicating that the MADS gene can regulate the growth and development of chayote, resist abiotic stress, and participate in hormone response; GO and KEGG enrichment analysis also found that SeMADS genes were mainly enriched in biological regulation and signal regulation, which further proved the important role of MADS-box gene in plant growth and development. The results of collinearity showed that segmental duplication was the main driving force of MADS gene expansion in chayote. RNA-seq showed that the expression levels of SeMADS06, SeMADS13, SeMADS26, SeMADS28, SeMADS36 and SeMADS37 gradually increased with the growth of chayote, indicating that these genes may be related to the development of root tubers of 'Tuershao'. The gene expression patterns showed that 12 SeMADS genes were specifically expressed in the male flower in 'Tuershao' and chayote. In addition, SeMADS03 and SeMADS52 may be involved in regulating the maturation of male flowers of 'Tuershao' and chayote. SeMADS21 may be the crucial gene in the development stage of the female flower of 'Tuershao'. This study laid a theoretical foundation for the further study of the function of the MADS gene in chayote in the future.

Coexistence and Coupling of Multiple Charge Orderings and Spin States in Hexagonal Ferrite.

The coupling between charge and spin orderings in strongly correlated systems plays a crucial role in fundamental physics and device applications. As a candidate of multiferroic materials, LuFe2O4 with a nominal Fe2.5+ valence state has the potential for strong charge-spin interactions; however, these interactions have not been fully understood until now. Here, combining complementary characterization methods with theoretical calculations, two types of charge orderings with distinct magnetic properties are revealed. The ground states of LuFe2O4 are decided by the parallel/antiparallel coupling of both charge and spin orderings in the adjacent FeO double layers. Whereas the ferroelectric charge ordering remains ferrimagnetic below 230 K, the antiferroelectric ordering undergoes antiferromagnetic-ferrimagnetic-paramagnetic transitions from 2 K to room temperature. This study demonstrates the unique aspects of strong spin-charge coupling within LuFe2O4. Our results shed light on the coexistence and competing nature of orderings in quantum materials.

Transcriptome and Metabolome Analysis Provide New Insights into the Process of Tuberization of Sechium edule Roots.

Chayote (Sechium edule) produces edible tubers with high starch content after 1 year of growth but the mechanism of chayote tuberization remains unknown. 'Tuershao', a chayote cultivar lacking edible fruits but showing higher tuber yield than traditional chayote cultivars, was used to study tuber formation through integrative analysis of the metabolome and transcriptome profiles at three tuber-growth stages. Starch biosynthesis- and galactose metabolism-related genes and metabolites were significantly upregulated during tuber bulking, whereas genes encoding sugars will eventually be exported transporter (SWEET) and sugar transporter (SUT) were highly expressed during tuber formation. Auxin precursor (indole-3-acetamide) and ethylene precursor, 1-aminocyclopropane-1-carboxylic acid, were upregulated, suggesting that both hormones play pivotal roles in tuber development and maturation. Our data revealed a similar tuber-formation signaling pathway in chayote as in potatoes, including complexes BEL1/KNOX and SP6A/14-3-3/FDL. Down-regulation of the BEL1/KNOX complex and upregulation of 14-3-3 protein implied that these two complexes might have distinct functions in tuber formation. Finally, gene expression and microscopic analysis indicated active cell division during the initial stages of tuber formation. Altogether, the integration of transcriptome and metabolome analyses unraveled an overall molecular network of chayote tuberization that might facilitate its utilization.

Bloch Chirality Induced by an Interlayer Dzyaloshinskii-Moriya Interaction in Ferromagnetic Multilayers.

Chiral spin textures stabilized by the interfacial Dzyaloshinkii-Moriya interaction, such as skyrmions and homochiral domain walls, have been shown to exhibit qualities that make them attractive for their incorporation in a variety of spintronic devices. However, for thicker multilayer films, mixed textures occur in which an achiral Bloch component coexists with a chiral Néel component of the domain wall to reduce the demagnetization field at the film surface. We show that an interlayer Dzyaloshinkii-Moriya interaction can break the degeneracy between Bloch chiralities. We further find large population asymmetries and chiral branching in the Bloch component of the domain walls in well-ordered Co/Pd multilayers. This asymmetry is a result of the combined effect of the demagnetization field and an interlayer Dzyaloshinkii-Moriya interaction, and is strongly related to film thickness and structural ordering. This work paves the way toward the utilization of this effect toward controlling Bloch chirality in magnetic multilayers.

Charge-Lattice Coupling in Hole-Doped LuFe_{2}O_{4+δ}: The Origin of Second-Order Modulation.

Understanding singularities in ordered structures, such as dislocations in lattice modulation and solitons in charge ordering, offers great opportunities to disentangle the interactions between the electronic degrees of freedom and the lattice. Specifically, a modulated structure has traditionally been expressed in the form of a discrete Fourier series with a constant phase and amplitude for each component. Here, we report atomic scale observation and analysis of a new modulation wave in hole-doped LuFe_{2}O_{4+δ} that requires significant modifications to the conventional modeling of ordered structures. This new modulation with an unusual quasiperiodic singularity can be accurately described only by introducing a well-defined secondary modulation vector in both the phase and amplitude parameter spaces. Correlated with density-functional-theory (DFT) calculations, our results reveal that those singularities originate from the discontinuity of lattice displacement induced by interstitial oxygen in the system. The approach of our work is applicable to a wide range of ordered systems, advancing our understanding of the nature of singularity and modulation.

Effect of Oxygen Interstitial Ordering on Multiple Order Parameters in Rare Earth Ferrite.

Oxygen interstitials and vacancies play a key role in modulating the microstructure and properties of nonstoichiometric oxide systems, such as those used for superconductors and multiferroics. Key to understanding the tuning mechanisms resulting from oxygen doping is a knowledge of the precise positions of these lattice defects, and of the interaction both between these defects and with many order parameters. Here, we report how such information can, for the first time, be obtained from a sample of LuFe_{2}O_{4.22} using a range of techniques including advanced electron microscopy, atomic-resolution spectroscopy, and density functional theory calculations. The results provide quantitative atomic details of the crystal unit cell, together with a description of the ferroelastic, ferroelectric, and ferromagnetic order parameters. We elucidate also the interaction between these order parameters and the positions of the oxygen interstitials in the oxygen-enriched sample. The comprehensive analysis of oxygen interstitial ordering provides insights into understanding the coupling among different degrees of freedom in rare earth ferrites and demonstrates that oxygen content regulation is a powerful tool for tuning the microstructure and properties for this class of quantum material.

High Efficiency Si Photocathode Protected by Multifunctional GaN Nanostructures.

Photoelectrochemical water splitting is a clean and environmentally friendly method for solar hydrogen generation. Its practical application, however, has been limited by the poor stability of semiconductor photoelectrodes. In this work, we demonstrate the use of GaN nanostructures as a multifunctional protection layer for an otherwise unstable, low-performance photocathode. The direct integration of GaN nanostructures on n+-p Si wafer not only protects Si surface from corrosion but also significantly reduces the charge carrier transfer resistance at the semiconductor/liquid junction, leading to long-term stability (>100 h) at a large current density (>35 mA/cm2) under 1 sun illumination. The measured applied bias photon-to-current efficiency of 10.5% is among the highest values ever reported for a Si photocathode. Given that both Si and GaN are already widely produced in industry, our studies offer a viable path for achieving high-efficiency and highly stable semiconductor photoelectrodes for solar water splitting with proven manufacturability and scalability.

Topologically Allowed Nonsixfold Vortices in a Sixfold Multiferroic Material: Observation and Classification.

We report structural transformation of sixfold vortex domains into two-, four-, and eightfold vortices via a different type of topological defect in hexagonal manganites. Combining high-resolution electron microscopy and Landau-theory-based numerical simulations, we investigate the remarkable atomic arrangement and the intertwined relationship between the vortex structures and the topological defects. The roles of their displacement field, formation temperature, and nucleation sites are revealed. All conceivable vortices in the system are topologically classified using homotopy group theory, and their origins are identified.

Cuticle properties, wax composition, and crystal morphology of Hami melon cultivars (Cucumis melo L.) with differential resistance to fruit softening.

Cuticle wax chemicals are cultivar-dependent and contribute to storage quality. Few research reported on wax analysis between melting flesh-type (MF; 'Jinhuami 25') and nonmelting flesh-type (NMF; 'Xizhoumi 17' and 'Chougua') Hami melons. Chemicals and crystal structures of Hami melon cuticular wax, cell wall metabolism related to fruit melting, and fruit physiology were analyzed to observe wax functions. Results showed that Hami melon cuticle wax predominantly consists of esters, alkanes, alcohols, aldehydes, and terpenoids. MF-type has a lower alkane/terpenoid ratio, concomitant to its higher weight loss and cuticle permeability. Micromorphology of wax crystals appears as numerous platelets with irregular crystals, and the transformation of wax structure in NMF Hami melon is delayed. Waxy components affect cell wall metabolism and physiological quality, which results in the pulp texture difference between MF-type and NMF-type during storage. Results provide a reference for the regulation of wax synthesis in both types of melons.

Effects of ultrasonication and freeze-thaw pretreatments on the vacuum freeze-drying process and quality characteristics of apricot (Prunus armeniaca L. cv. Diaoganxing).

The combination of pretreatment and vacuum freeze-drying (VFD) technology is an effective technique for extending the shelf life of apricots, reducing costs and energy consumption. However, the impact of pretreatment on the freeze-drying and quality characteristics of apricots is still unclear. The effects of ultrasound (US), freeze-thaw (FT), and their combination (FT-US) on water migration and quality characteristics of apricot slices on VFD were studied. LR-NMR and SEM showed that pretreatment significantly reduced the time (19.05%-33.33%) and energy consumption (17.67%-35.66%) of the VFD process. Compared with the control group, the US, FT, and FT-US improved the color, texture, rehydration ability, and flavor of apricot slices. Among them, FT-US retained the most biologically active substances and antioxidant capacity, with the highest sensory score. Overall, FT-US pretreatment induced changes in the microstructure and chemistry of apricots, which contributed to the production of high-quality VFD apricot slices.

Effects of variable-temperature drying on the qualities and sweet-substance profile of Zizyphus jujuba Mill. cv. Junzao.

The changes in the qualities and sweet-substance levels of Junzao jujube during variable-temperature drying (VTD) were investigated. The results showed that VTD retains the original color of jujube, reduces its hardness and chewiness, and decreases its wrinkling while shortening the drying time by 13.2% compared with that of constant temperature drying (CTD). "Electronic-tongue" taste analysis showed that the sweetness of VTD jujube is significantly higher than that for CTD. This is shown to be related to the contents of sucrose, fructose, and glucose, as well as the activities of invertase and sucrose synthase enzymes. In addition, the content trends for sweet amino acids are correlated with the temperature gradient used in VTD. Thus, the present study elucidates the factors governing the transformation of sugar substances in jujube during VTD, as well as providing a practical reference for the application of VTD in the jujube industry.