Search

The performances of porous graphitic foams in flexible electronic, electrochemical, and thermal management devices can be enhanced by increasing the interfacial charge or heat transport between the 3D graphitic network and the functional materials filled into the pore space. Herein, an investigation of the effects of chemical vapor deposition (CVD) conditions on the structure and thermal conductivities of both graphitic foams grown from reticular Ni foams and dendritic graphitic foams (DGFs) synthesized from electrodeposited dendritic Ni foams is reported. A room‐temperature solid thermal conductivity (κs) up to 800 W m−1 K−1 is obtained from the graphitic foams (GF) with less than 1% volume fraction. In comparison, the DGFs, which provide a large increase of the specific surface area for enhanced interfacial heat transfer, achieve an effective thermal conductivity of 2.5 ± 0.2 W m−1 K−1 because of an enhanced volume fraction to about 5% despite a compromised κs around 200 W m−1 K−1 due to the increased defect density. Through systematical variations of the catalyst template morphology and CVD conditions, this work reveals the distinct roles of catalyst surface curvature and graphitic strut thickness in controlling the properties of GFs and DGFs for thermal management. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are plant metabolic and signaling molecules involved in responses to various external stresses, but the existence of ROS receptors and how plants respond to ROS remain largely unknown. Here we report that the plasma membrane-localized phospholipase D δ (PLDδ) protein is crucial for sensing heat shock-induced ROS to initiate reorganization of guard cell microtubules in Arabidopsis cotyledons. Heat shock of wild-type Arabidopsis cotyledons stimulated ROS production which disrupted microtubule organization and induced stomatal closure, whereas this process was markedly impaired in pldδ mutants. Moreover, wild-type PLDδ, but not the Arg622-mutated PLDδ, complemented the pldδ phenotypes in heat shock-treated plants. ROS activated PLDδ by oxidizing cysteine residues, an action that was required for its functions in ROS-induced depolymerization of guard cell microtubules, stomatal closure, and plant thermotolerance. Additionally, lipid profiling reveals involvement of microtubule organization in the feedback regulation of glycerolipid metabolism upon heat stress. Together, our findings highlight a potential mechanosensory role for PLDδ in regulating the dynamic organization of microtubules and stomatal movement, as part of the ROS-sensing pathway, during the response to external stresses. [ABSTRACT FROM AUTHOR]

• A differential electro-thermal bridge measurement is established to enhance the signal-tonoise ratio and obtain over 40% reduction in the uncertainty in the measured thermal resistance of individual multi-walled carbon nanotubes (MWCNTs). • The measured interface thermal resistance is used to obtain the sample temperature profile at the contact and eliminate the contact thermal resistance error in the measured thermal conductivity of the suspended sample segment. • The measured thermal resistances of multiple suspended segments of the same MWCNT increase linearly with length, revealing diffusive phonon transport due to phonon-defect scattering. • Theoretical analysis of the measurement results suggests submicron phonon mean free paths due to extrinsic phonon scattering by extended defects such as grain boundaries. • Electron beam damage and surface amorphous coating of the nanotube decreases the obtained thermal conductivity by a factor of 3. Carbon nanotubes (CNTs) are quasi-one dimensional nanostructures that display both high thermal conductivity for potential thermal management applications and intriguing low-dimensional phonon transport phenomena. In comparison to the advances made in the theoretical calculation of the lattice thermal conductivity of CNTs, thermal transport measurements of CNTs have been limited by either the poor temperature sensitivity of Raman thermometry technique or the presence of contact thermal resistance errors in sensitive two-probe resistance thermometry measurements. Here we report advances in a multi-probe measurement of the intrinsic thermal conductivity of individual multi-walled CNT samples that are transferred from the growth substrate onto the measurement device. The sample-thermometer thermal interface resistance is directly measured by this multi-probe method and used to model the temperature distribution along the contacted sample segment. The detailed temperature profile helps to eliminate the contact thermal resistance error in the obtained thermal conductivity of the suspended sample segment. A differential electro-thermal bridge measurement method is established to enhance the signal-to-noise ratio and reduce the measurement uncertainty by over 40%. The obtained thermal resistances of multiple suspended segments of the same MWCNT samples increase nearly linearly with increasing length, revealing diffusive phonon transport as a result of phonon-defect scattering in these MWCNT samples. The measured thermal conductivity increases with temperature and reaches up to 390 ± 20 W m−1 K−1 at room temperature for a 9-walled MWCNT. Theoretical analysis of the measurement results suggests submicron phonon mean free paths due to extrinsic phonon scattering by extended defects such as grain boundaries. The obtained thermal conductivity is decreased by a factor of 3 upon electron beam damage and surface contamination of the CNT sample. [ABSTRACT FROM AUTHOR]

• Sintered Ni powder templates are used for catalytic growth of h-BN foams to increase the effective thermal conductivity. • The solid thermal conductivity of the h-BN struts is comparable to reported first principles calculation results. • The effective thermal conductivity of h-BN foam-polymer composites is insensitive to the interface thermal resistance. Continuous and porous foam structures of thermally conducting and electrically insulating hexagonal boron nitride (h-BN) have been synthesized for heat dissipation and other applications. However, the volume fraction and effective thermal conductivity of existing h-BN foam structures are still limited by the large pore size and small specific surface area of the sacrificial reticular nickel foam templates used for chemical vapor deposition (CVD) of h-BN. Here we report experiments for increasing the volume fraction and effective thermal conductivity of CVD h-BN foams with the use of sintered nickel powder templates with reduced pore sizes. The volume fraction of the obtained high-surface area h-BN foam sample HS1 reaches 0.34 ± 0.06 %, which is an increase by a factor of 2.8 compared to a baseline h-BN foam grown on a reticulated nickel foam with the same growth time. Increasing the growth time by a factor of 3 results in a further increase of the volume fraction by an additional factor of 2 for sample HS2. With poly(methyl methacrylate) (PMMA) filled into the pore space of the h-BN foam, the room-temperature effective thermal conductivity of the composite increases from 0.31 ± 0.02 W m−1 K−1 for the baseline structure to 0.70 ± 0.05 W m−1 K−1 for HS2. Based on numerical analysis of the measured effective thermal conductivity, the solid thermal conductivity of the h-BN struts of the baseline structure is 580 ± 150 W m−1 K−1, which is comparable to a prior first principles calculation. The increases in the volume fraction and effective thermal conductivity are accompanied by a reduction of the h-BN solid thermal conductivity to 410 ± 80 W m−1 K−1 for HS1 and 250 ± 30 W m−1 K−1 for HS2 due to increased defect concentrations and surface curvature. The numerical simulation reveals that the thermal interface resistance between h-BN and PMMA plays only a small role on the effective thermal conductivity due to the dominant thermal transport contribution from the continuous high-thermal conductivity struts. [ABSTRACT FROM AUTHOR]

The dynamic changes in membrane phospholipids affect membrane biophysical properties and cell signaling, thereby influencing numerous biological processes. Nonspecific phospholipase C (NPC) enzymes hydrolyze common phospholipids to release diacylglycerol (DAG), which is converted to phosphatidic acid (PA) and other lipids. In this study, 2 Arabidopsis (Arabidopsis thaliana) tandemly arrayed genes, NPC3 and NPC4, were identified as critical factors modulating auxin-controlled plant growth and tropic responses. Moreover, NPC3 and NPC4 were shown to interact with the auxin efflux transporter PIN-FORMED2 (PIN2). The loss of NPC3 and NPC4 enhanced the endocytosis and vacuolar degradation of PIN2, which disrupted auxin gradients and slowed gravitropic and halotropic responses. Furthermore, auxin-triggered activation of NPC3 and NPC4 is required for the asymmetric PA distribution that controls PIN2 trafficking dynamics and auxin-dependent tropic responses. Collectively, our study reveals an NPC-derived PA signaling pathway in Arabidopsis auxin fluxes that is essential for fine-tuning the balance between root growth and environmental responses. Nonspecific phospholipases NPC3 and NPC4 interact with the transporter PIN-FORMED2 and regulate auxin transport and signaling. [ABSTRACT FROM AUTHOR]

Background: Cadmium (Cd) is extremely toxic and non-essential for plants. Different soybean varieties differ greatly in their Cd accumulation ability, but little is known about the underlying molecular mechanisms. Results: Here, we performed transcriptomic analysis using Illumina pair-end sequencing on root tissues from two soybean varieties (su8, high-Cd-accumulating (HAS) and su7, low Cd-accumulating (LAS)) grown with 0 or 50 μM CdSO4. A total of 18.76 million clean reads from the soybean root samples were obtained after quality assessment and data filtering. After Cd treatment, 739 differentially expressed genes (DEGs; 265 up and 474 down) were found in HAS; however, only 259 DEGs (88 up and 171 down) were found in LAS, and 64 genes were same between the two varieties. Pathway enrichment analysis suggested that after cadmium treatment, the DEGs between LAS and HAS were mainly enriched in glutathione metabolism and plant-pathogen interaction pathways. KEGG analysis showed that phenylalanine metabolism responding to cadmium stress in LAS, while ABC transporters responding to cadmium stress in HAS. Besides we found more differential expressed heavy metal transporters such as ABC transporters and zinc transporters in HAS than LAS, and there were more transcription factors differently expressed in HAS than LAS after cadmium treatment in two soybean varieties, eg. bHLH transcription factor, WRKY transcription factor and ZIP transcription factor. Conclusions: Findings from this study will shed new insights on the underlying molecular mechanisms behind the Cd accumulation in soybean. [ABSTRACT FROM AUTHOR]

The colorations of stem pubescence and hilum are crucial criteria for discerning diverse soybean germplasms, governed by multiple genes that substantially influence the seed's outward appearance quality and the resistance to abiotic stresses. This comprehensive study delved into the stem pubescence and hilum color traits across a natural population of 264 accessions during 2021 and 2022. The phenotypes of these two traits within our population were analyzed for the investigation of population genetics and evaluation of germplasm resources in the future. Numerous noteworthy SNPs associated with both traits were detected through a genome-wide association study (GWAS), with the most significant signals for 2021 and 2022 localized on chromosome 6. Seven candidate genes regulating stem pubescence color and four genes influencing hilum color were identified by analyzing the expression patterns, cold stress responses, and regulatory pathways of genes within the LD decay distance of SNPs. This study not only underscores the applicability of GWAS in unraveling the genetic basis of quality traits, but also contributes novel genetic reservoirs and research paradigms to the explorations of the soybean plant and seed color. These results provide foundational insights into the breeding improvement of seeds' outward appearance quality and a comprehensive evaluation of soybean germplasm. [ABSTRACT FROM AUTHOR]

The spin ladder compound (Sr,Ca,La)14Cu24O41 exhibits an incommensurate layered structure with strong antiferromagnetic coupling. Besides intriguing superconducting behavior, recent experiments on bulk Sr14Cu24O41 single crystals have revealed a remarkable magnon thermal conductivity, which is the largest above 100 K among all known quantum magnets. Although bulk (Sr,Ca,La)14Cu24O41 crystals have been synthesized and studied extensively, there have been few reports on the synthesis and magnon thermal transport investigation of their microstructures. Here, the synthesis and thermal transport properties of Sr14Cu24O41 microrods are reported. Electron microscopy studies indicate that these microrods synthesized by a coprecipitation method are single crystals grown preferentially along the ladder axis. Based on a four‐probe thermal transport measurement, the thermal conductivity of the microrods reveals appreciable magnon transport in the microstructures. According to a kinetic model analysis, magnon transport in the microrods is suppressed mainly by increased point defect scattering compared to the bulk crystals, whereas surface scattering is negligible for anisotropic 1D magnon transport along the ladder. Moreover, the thermal conductivity is enhanced after annealing as a result of reduced oxygen vacancies. These results help to build the foundation for future heterogeneous integration of magnetic microstructures in microscale devices for the transport of energy and quantum information. [ABSTRACT FROM AUTHOR]

The pattern of cortical microtubule arrays plays an important role in plant growth and adaptation in response to hormonal and environmental changes. Cortical microtubules are connected with the plasma membrane (PM); however, how the membrane affects cortical microtubule organization is not well understood. Here, we showed that phospholipase Dδ (PLDδ) was associated with the PM and co-localized with microtubules in cells. In vitro analysis revealed that PLDδ bound to microtubules, resulting in microtubule disorganization. Site-specific mutations that decreased PLDδ enzymatic activity impaired its effects on destabilizing microtubule organization. Heat shock transiently activated PLDδ, without any change of its PM localization, triggering microtubule dissociation from PM and depolymerization and seedling death in Arabidopsis, but these effects were alleviated in pldδ knockout mutants. Complementation of pldδ with wild-type PLDδ, but not mutated PLDδ, restored the phenotypes of microtubules and seedling survival to those of wild-type Arabidopsis. Thus, we conclude that the PM-associated PLDδ negatively regulates plant thermotolerance via destabilizing cortical microtubules, in an activity-dependent manner, rather than its subcellular translocation. [ABSTRACT FROM AUTHOR]

Phospholipase D (PLD) and its product phosphatidic acid (PA) are emerging as essential regulators of cytoskeleton organization in plants. However, the underlying molecular mechanisms of PA-mediated microtubule reorganization in plants remain largely unknown. In this study, we used pharmacological and genetic approaches to analyze the function of Arabidopsis thaliana PLDα1 in the regulation of microtubule organization and cell development in response to microtubule-affecting drugs. Treatment with the microtubule-stabilizing drug paclitaxel resulted in less growth inhibition and decreased rightward slant of roots, longitudinal alignment of microtubules, and enhanced length of hypocotyl epidermal cells in the pldα1 mutant, the phenotype of which was rescued by exogenous application of PA. Moreover, the pldα1 mutant was sensitive to the microtubule-disrupting drugs oryzalin and propyzamide in terms of seedling survival ratio, left-skewing angle of roots and microtubule organization. In addition, both disruption and stabilization of microtubules induced by drugs activated PLDα1 activity. Our findings demonstrate that in A. thaliana, PLDα1/PA might regulate cell development by modulating microtubule organization in an activity-dependent manner. [ABSTRACT FROM AUTHOR]

Glycerol-3-phosphate acyltransferases (GPATs) play an important role in glycerolipid biosynthesis, and are mainly involved in oil production, flower development, and stress response. However, their roles in regulating plant height remain unreported. Here, we report that Arabidopsis GPAT1 is involved in the regulation of plant height. GUS assay and qRT-PCR analysis in Arabidopsis showed that GPAT1 is highly expressed in flowers, siliques, and seeds. A loss of function mutation in GPAT1 was shown to decrease seed yield but increase plant height through enhanced cell length. Transcriptomic and qRT-PCR data revealed that the expression levels of genes related to gibberellin (GA) biosynthesis and signaling, as well as those of cell wall organization and biogenesis, were significantly upregulated. These led to cell length elongation, and thus, an increase in plant height. Together, our data suggest that knockout of GPAT1 impairs glycerolipid metabolism in Arabidopsis, leading to reduced seed yield, but promotes the biosynthesis of GA, which ultimately enhances plant height. This study provides new evidence on the interplay between lipid and hormone metabolism in the regulation of plant height. [ABSTRACT FROM AUTHOR]

• Phospholipase D (PLD) hydrolyzes glycerophospholipids to yield phosphatidic acid and a free headgroup. • GmPLDγ is targeted to mitochondria and exhibits PLD activity. • Overexpression of GmPLDγ from soybean results in higher seed oil content and fatty-acid remodeling in Arabidopsis. Phospholipase D (PLD) hydrolyzes the phosphodiester bond of glycerophospholipids to yield phosphatidic acid (PA) and a free headgroup. PLDs are important for plant growth, development, and responses to external stresses. However, their roles in triacylglycerol (TAG) synthesis are still unclear. Here, we report that a soybean (Glycine max) PLDγ (GmPLDγ) is involved in glycerolipid turnover and seed oil production. GmPLDγ was targeted to mitochondria and exhibited PLD activity that was activated by oleate and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2 ]. Overexpression of GmPLDγ (abbreviated GmPLDγ -OE) in Arabidopsis thaliana resulted in enhanced seed weight, elevated levels of TAGs with 18-, 20-, and 22-carbon fatty acids (FAs), and altered oil-body morphology. Furthermore, the levels of membrane lipids in vegetative tissues decreased significantly, whereas no overt changes were found in mature seeds except for a decrease in the digalactosyldiacylglycerol (DGDG) level in the GmPLDγ -OE lines. Additionally, the expression of genes involved in glycerolipid metabolism was significantly upregulated in developing siliques in GmPLDγ -OE lines. Together, our data indicate a regulatory role for GmPLDγ in TAG synthesis and fatty-acid remodeling, highlighting the importance of mitochondria-directed glycerophospholipid homeostasis in seed oil accumulation. [ABSTRACT FROM AUTHOR]