PtoMYB031, the R2R3 MYB transcription factor involved in secondary cell wall biosynthesis in poplar

IntroductionThe biosynthesis of the secondary cell wall (SCW) is orchestrated by an intricate hierarchical transcriptional regulatory network. This network is initiated by first-layer master switches, SCW-NAC transcription factors, which in turn activate the second-layer master switches MYBs. These switches play a crucial role in regulating xylem specification and differentiation during SCW formation. However, the roles of most MYBs in woody plants are yet to be fully understood.MethodsIn this study, we identified and isolated the R2R3-MYB transcription factor, PtoMYB031, from Populus tomentosa. We explored its expression, mainly in xylem tissues, and its role as a transcriptional repressor in the nucleus. We used overexpression and RNA interference techniques in poplar, along with Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays, to analyze the regulatory effects of PtoMYB031.ResultsOverexpression of PtoMYB031 in poplar significantly reduced lignin, cellulose, and hemicellulose content, and inhibited vascular development in stems, resulting in decreased SCW thickness in xylem tissues. Gene expression analysis showed that structural genes involved in SCW biosynthesis were downregulated in PtoMYB031-OE lines. Conversely, RNA interference of PtoMYB031 increased these compounds. Additionally, PtoMYB031 was found to recruit the repressor PtoZAT11, forming a transcriptional inhibition complex.DiscussionOur findings provide new insights into how PtoMYB031, through its interaction with PtoZAT11, forms a complex that can suppress the expression of key regulatory genes, PtoWND1A and PtoWND2B, in SCW biosynthesis. This study enhances our understanding of the transcriptional regulation involved in SCW formation in poplar, highlighting the significant role of PtoMYB031

Future directions in ventilator-induced lung injury associated cognitive impairment: a new sight

Mechanical ventilation is a widely used short-term life support technique, but an accompanying adverse consequence can be pulmonary damage which is called ventilator-induced lung injury (VILI). Mechanical ventilation can potentially affect the central nervous system and lead to long-term cognitive impairment. In recent years, many studies revealed that VILI, as a common lung injury, may be involved in the central pathogenesis of cognitive impairment by inducing hypoxia, inflammation, and changes in neural pathways. In addition, VILI has received attention in affecting the treatment of cognitive impairment and provides new insights into individualized therapy. The combination of lung protective ventilation and drug therapy can overcome the inevitable problems of poor prognosis from a new perspective. In this review, we summarized VILI and non-VILI factors as risk factors for cognitive impairment and concluded the latest mechanisms. Moreover, we retrospectively explored the role of improving VILI in cognitive impairment treatment. This work contributes to a better understanding of the pathogenesis of VILI-induced cognitive impairment and may provide future direction for the treatment and prognosis of cognitive impairment

Lineage diversification and historical demography of a montane bird Garrulax elliotii - implications for the Pleistocene evolutionary history of the eastern Himalayas

<p>Abstract</p> <p>Background</p> <p>Pleistocene climate fluctuations have shaped the patterns of genetic diversity observed in many extant species. In montane habitats, species' ranges may have expanded and contracted along an altitudinal gradient in response to environmental fluctuations leading to alternating periods of genetic isolation and connectivity. Because species' responses to climate change are influenced by interactions between species-specific characteristics and local topography, diversification pattern differs between species and locations. The eastern Himalayas is one of the world's most prominent mountain ranges. Its complex topography and environmental heterogeneity present an ideal system in which to study how climatic changes during Pleistocene have influenced species distributions, genetic diversification, and demography. The Elliot's laughing thrush (<it>Garrulax elliotii</it>) is largely restricted to high-elevation shrublands in eastern Himalayas. We used mitochondrial DNA and microsatellites to investigate how genetic diversity in this species was affected by Pleistocene glaciations.</p> <p>Results</p> <p>Mitochondrial data detected two partially sympatric north-eastern and southern lineages. Microsatellite data, however, identified three distinct lineages congruent with the geographically separated southern, northern and eastern eco-subregions of the eastern Himalayas. Geographic breaks occur in steep mountains and deep valleys of the Kangding-Muli-Baoxin Divide. Divergence time estimates and coalescent simulations indicate that lineage diversification occurred on two different geographic and temporal scales; recent divergence, associated with geographic isolation into individual subregions, and historical divergence, associated with displacement into multiple refugia. Despite long-term isolation, genetic admixture among these subregional populations was observed, indicating historic periods of connectivity. The demographic history of <it>Garrulax elliotii </it>shows continuous population growth since late Pleistocene (about 0.125 mya).</p> <p>Conclusion</p> <p>While altitude-associated isolation is typical of many species in other montane regions, our results suggest that eco-subregions in the eastern Himalayas exhibiting island-like characteristics appear to have determined the diversification of <it>Garrulax elliotii</it>. During the Pleistocene, these populations became isolated on subregions during interglacial periods but were connected when these expanded to low altitude during cooler periods. The resultant genetic admixture of lineages might obscure pattern of genetic variation. Our results provide new insights into sky island diversification in a previously unstudied region, and further demonstrate that Pleistocene climatic changes can have profound effects on lineage diversification and demography in montane species.</p

Experimental and Numerical Analysis of Progressive Damage of SiC_f/SiC Composite under Three-Point Bending

Satin SiCf/SiC composite has a wide range of applications; it is necessary to study its mechanical properties. The progressive failure of five-harness five-layer satin weave SiCf/SiC plate composites was explored experimentally and numerically in this research. The bending properties were derived and elucidated at ambient temperature through a three-point bending experiment. The generation and progression of damage was observed by CCD camera. For quantitative analysis of the strain field evolution, DIC (digital image correlation) was adopted, while the microscopic analyses were performed for the description of the derived failure markings. With the aid of ABAQUS/Explicit, the experiment was subjected to 3D finite element modeling for the reproduction of the material behavioral, where the VUMAT subroutine was used to implement a 3D-altered criterion of the Hashin damage initiation and the progression law of its complementary damage. Intra-deformation interface failure was simulated with a composite interlayer cohesive zone element. The experimentally derived DIC-based strain fields were well-consistent with the numerical outcomes. Deeper investigation was made into the superiority of the 3D modeling, which is ascribed to the predictability for distribution of complex field variables like the free-edge effect and progressive failure accumulation within the critical sample section. The damage mechanism of the satin weave composite was explored in depth and it provides useful guidance for the practical application of the composite

Microstructure and Mechanical Properties of Carbon/Carbon Composites Infiltrated with Ti–6Al–4V Titanium Alloy

In this work, chemical vapor infiltration (CVI) was combined with reactive melt infiltration (RMI) using Ti&ndash;6Al&ndash;4V titanium alloy powder to prepare Cf/C&ndash;TiC composites. The microstructure and composition of Cf/C&ndash;TiC composites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The flexural properties of the composites were also analyzed. The results indicated that the Ti&ndash;6Al&ndash;4V titanium alloy infiltrated the Cf/C preform and reacted with the pyrolytic carbon (PyC) to form a TiC&ndash;VC and Al4C3 matrix, and no residual Ti, Al, or V was detected. Moreover, Al4C3 was concentrated and independently distributed, whereas Ti and V reacted with C to form a TiC&ndash;VC solid solution. The porosity was 6.75%, and the bulk density of Cf/C&ndash;TiC was 1.96 g/cm3. The flexural strength, flexural modulus, and failure strains were 256 &plusmn; 18 MPa, 89 &plusmn; 9 GPa, and 0.93 &plusmn; 0.13%, respectively. The work of fracture of the Cf/C&ndash;TiC composite was about 6.8 &plusmn; 0.38 KJ/m2. Due to the propagation and deflection of cracks, as well as debonding and fiber pullout, the Cf/C&ndash;TiC composite showed ductile fracture behavior

Experimental and Numerical Study on the Bending Behavior of Satin-Woven SiCf/SiC Composites

The present research intends to explore the progressive failure in the case of five-harness SiCf/SiC satin-woven sheet composites consisting of twelve layers using a combination of numerical and experimental methods. For derivation and characterization of the bending behavior, a three-point bending procedure was used under conditions of atmospheric temperature. A charge-coupled device (CCD) camera was used to monitor the initiation and evolution of the failures. Variations in the strain fields were quantified following the digital image correlation (DIC) approach, whereas the resultant failure markings were elucidated by conducting microscopic assessments. The 3D finite element modeling (FEM) of the experiment was accomplished via ABAQUS/Explicit, thereby reproducing the material performance. A 3D-modified theory of the Tsai-Wu failure initiation was executed by exploiting the VUMAT subroutine. The evolutionary rule was used to study the complementary failure. A cohesive zone element of the composite interlayer was utilized to mimic the intra-deformation interfacial damage. The DIC-based experimental values of the strain fields agreed favorably with the numerical computations and the strength value error was less than 10%. An in-depth investigation was performed concerning the advantage of the 3D modeling approach to study the applicability of the method for the foreseeable distribution of the complex field parameters (e.g., progressive failure deposition and free edge effect) inside the critical specimen section

Carbon Fiber Reinforced Carbon–Al–Cu Composite for Friction Material

A carbon/carbon–Al–Cu composite reinforced with carbon fiber 2.5D-polyacrylonitrile-based preforms was fabricated using the pressureless infiltration technique. The Al–Cu alloy liquids were successfully infiltrated into the C/C composites at high temperature and under vacuum. The mechanical and metallographic properties, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) of the C/C–Al–Cu composites were analyzed. The results showed that the bending property of the C/C–Al–Cu composites was 189 MPa, whereas that of the pure carbon slide material was only 85 MPa. The compressive strength of C/C–Al–Cu was 213 MPa, whereas that of the pure carbon slide material was only 102 MPa. The resistivity of C/C–Al–Cu was only 1.94 μΩm, which was lower than that of the pure carbon slide material (29.5 μΩm). This finding can be attributed to the “network conduction” structure. Excellent wettability was observed between Al and the carbon matrix at high temperature due to the existence of Al4C3. The friction coefficients of the C/C, C/C–Al–Cu, and pure carbon slide composites were 0.152, 0.175, and 0.121, respectively. The wear rate of the C/C–Al–Cu composites reached a minimum value of 2.56 × 10−7 mm3/Nm. The C/C–Al–Cu composite can be appropriately used as railway current collectors for locomotives

Effect of Interface Modified by Graphene on the Mechanical and Frictional Properties of Carbon/Graphene/Carbon Composites

In this work, we developed an interface modified by graphene to simultaneously improve the mechanical and frictional properties of carbon/graphene/carbon (C/G/C) composite. Results indicated that the C/G/C composite exhibits remarkably improved interfacial bonding mode, static and dynamic mechanical performance, thermal conductivity, and frictional properties in comparison with those of the C/C composite. The weight contents of carbon fibers, graphene and pyrolytic carbon are 31.6, 0.3 and 68.1 wt %, respectively. The matrix of the C/G/C composite was mainly composed of rough laminar (RL) pyrocarbon. The average hardness by nanoindentation of the C/G/C and C/C composite matrices were 0.473 and 0.751 GPa, respectively. The flexural strength (three point bending), interlaminar shear strength (ILSS), interfacial debonding strength (IDS), internal friction and storage modulus of the C/C composite were 106, 10.3, 7.6, 0.038 and 12.7 GPa, respectively. Those properties of the C/G/C composite increased by 76.4%, 44.6%, 168.4% and 22.8%, respectively, and their internal friction decreased by 42.1% in comparison with those of the C/C composite. Owing to the lower hardness of the matrix, improved fiber/matrix interface bonding strength, and self-lubricating properties of graphene, a complete friction film was easily formed on the friction surface of the modified composite. Compared with the C/C composite, the C/G/C composite exhibited stable friction coefficients and lower wear losses at simulating air-plane normal landing (NL) and rejected take-off (RTO). The method appears to be a competitive approach to improve the mechanical and frictional properties of C/C composites simultaneously

Effect of Al–Mg Alloy Infiltration on Mechanical and Electrical Properties for Carbon/Carbon Composites

Under vacuum Al&ndash;Mg alloy, liquids were successfully infiltrated into carbon/carbon (C/C) composites at high temperatures. Then, the mechanical properties, the metallographics, the scanning electron microscope images, the transmission electron microscope images, the X-ray diffraction images, and the energy dispersive spectroscopy results of C/C&ndash;Al&ndash;Mg composites were analyzed. The result showed that the bending property of C/C&ndash;Al&ndash;Mg composites reached 183 MPa whereas that of C/C composites totaled 165 MPa. The compressive strength of C/C&ndash;Al&ndash;Mg measured 206 MPa whereas that of C/C composites amounted to 142 MPa. The flexural strength and compressive strengths of the steeped metal sliders measured 121 and 104 MPa, respectively. The alloy liquid infiltrated into the matrix by forming a &ldquo;network conduction&rdquo; structure which reduced the resistivity and improved the conductivity of the composites. The resistivity of C/C&ndash;Al&ndash;Mg totaled 1.63 &micro;&Omega;m whereas that of C/C was 3.56 &mu;&Omega;m. During infiltration, an excellent wettability was observed between Al and the carbon matrix due to the existence of Al4C3. The friction coefficients of C/C, the steeped metal slide, and C/Al&ndash;Mg were 0.152, 0.068, and 0.189, respectively. The properties of C/C&ndash;Al&ndash;Mg composites meet the performance requirements of locomotive pantograph sliders

Evaluation of Urban Ecosystem Service Value under New Urbanization—A Case Study of Chengdu City

In order to evaluate the change of ecosystem service value in Chengdu, GIS technology was used to obtain the land use type data of Chengdu from 2009 to 2018. The equivalent factor method was used as the core evaluation method, and an ecosystem value evaluation model was established to explore the impact of various land use types on ecosystem service value. The results show that: (1) the trend of land use change is that both the area and the proportion of land use change in different degrees. The area of cultivated land, water area and unused land are greatly reduced, and the area of construction land expands rapidly, mainly through the occupation of cultivated land and unused land. (2) The intensity of land use in Chengdu is greater and continues to increase, and the contribution rate of construction land is larger, which indicates that the land use structure is developing towards the structural direction of mainly construction land. (3) Changes in ecosystem service value are not only related to land use structure, but also to the economic development, willingness to pay and ability of the whole society. (4) Ecosystem service value is negatively correlated with construction land and unused land; it is positively correlated with cultivated land, forest land and grassland. Generally speaking, Chengdu’s land use change has not caused obvious damage to the ecosystem, but the impact of human lifestyle on the environment in the process of economic development cannot be ignored. The growth of construction land area should be appropriately controlled, ecological land should be protected, and the sustainable development of social-economic-ecological benefits should be realized