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The 1-3 piezoelectric composite is the key component of the acoustic transducer, which is widely used in detection, due to the high energy conversion efficiency, cheap raw material, and low aging. To reveal the influence of epoxy mixture, used to connect the piezoelectric column, on the composite performance, a 1-3 piezoelectric composite model was built. The effects of mixture properties on the impedance curves, vibration mode, and deformation displacement of the composite were determined. Six 1-3 piezoelectric composites with different filling mixture properties, by changing the glass microspheres' mass ratio in the epoxy, were prepared and measured to validate the model. The results showed that with the increase in the proportion of the glass microsphere in the epoxy mixture, the vibration coupling of the piezoelectric composites was gradually eliminated. The acoustic impedance was reduced by 12%. The electromechanical coupling coefficient and effective electromechanical coupling coefficient were increased by 5.4% and 8.3%, respectively. The density and Young's modulus decrease in filling mixture can significantly improve piezoelectric composite performance.
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BACKGROUND AND AIM: Patients with inflammatory bowel disease (IBD) often have the condition of malnutrition, which can be presented as sarcopenia, micronutrient deficiencies, etc. Trace elements (magnesium, calcium, iron, copper, zinc, plumbum and manganese) belonging to micronutrients, are greatly vital for the assessment of nutritional status in humans. Trace element deficiencies are also the main manifestation of malnutrition. Calcium (Ca) has been proved to play an important part in maintaining body homeostasis and regulating cellular function. However, there are still a lack of studies on the association between malnutrition and Ca deficiency in IBD. This research aimed to investigate the role of Ca for malnutrition in IBD patients. METHODS: We prospectively collected blood samples from 149 patients and utilized inductively coupled plasma mass spectrometry to examine their venous serum trace element concentrations. Logistic regression analyses were used to investigate the association between Ca and malnutrition. Receiver operating characteristic (ROC) curves were generated to calculate the cutoffs for determination of Ca deficiency. RESULTS: Except Ca, the concentrations of the other six trace elements presented no statistical significance between non-malnutrition and malnutrition group. In comparison with the non-malnutrition group, the serum concentration of Ca decreased in the malnutrition group (89.36 vs 87.03 mg/L, p = 0.023). With regard to ROC curve, Ca < 87.21 mg/L showed the best discriminative capability with an area of 0.624 (95% CI: 0.520, 0.727, p = 0.023). Multivariate analyses demonstrated that Ca < 87.21 mg/L (OR = 3.393, 95% CI: 1.524, 7.554, p = 0.003) and age (OR = 0.958, 95% CI: 0.926, 0.990, p = 0.011) were associated with malnutrition risk. Serum Ca levels were significantly lower in the malnutrition group than those in the non-malnutrition group among UC patients, those with severe disease state or the female group. CONCLUSIONS: In patients with IBD, Ca deficiency is an independent factor for high malnutrition risk.
Subject(s)
Calcium , Inflammatory Bowel Diseases , Malnutrition , Humans , Female , Malnutrition/blood , Malnutrition/epidemiology , Male , Calcium/blood , Inflammatory Bowel Diseases/complications , Inflammatory Bowel Diseases/blood , Adult , Middle Aged , Prospective Studies , Trace Elements/deficiency , Trace Elements/blood , Nutritional Status , ROC Curve , Risk Factors , AgedABSTRACT
When pipe defects are generated above the T-type support structure location, it is difficult to distinguish the reflection signals caused by the weld bead at the support structure from the reflection echoes of pipe defects. Therefore, in order to effectively detect pipe defects, a waveform subtraction method with a circumferential shear horizontal (CSH) guided wave is proposed, which is generated by an electromagnetic acoustic transducer (EMAT). First, a CSH0 guided wave mode with a center frequency of 500 kHz is selected to establish a three-dimensional model with and without pipe defects above the support structure. Following this, the influence of different widths of support structures on the echo signal is compared. Moreover, simulation and experimental results are used to compare the influence of different welding qualities on the detection results. Finally, the waveform subtraction method is used to process the simulation and experimental signals, and the influence of pipe defects with different lengths and depths is discussed. The results show that the non-through crack defect of 5 mm × 1 mm (length × depth) can be detected. The results show that this method can effectively detect the cracks by eliminating the influence of the weld echo, which provides a new concept for the detection of the defect above the support structure.
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In this paper, we use molecular dynamics to simulate the crack propagation behavior of gradient nano-grained (GNG) copper models with different grain size gradients, compare the crack propagation rates of different models, and analyze the microstructural changes and the mechanism of crack propagation. The simulation results show that the increase of the grain size gradient of the GNG copper model can improve the fracture resistance of the material, and the crack propagation mode undergoes a transition from brittle propagation along the grain boundaries to the formation of pores at the grain boundaries, and then to ductile fracture along the inclined plastic shear zone. The number of dislocations increases with the grain size gradient, while the crack passivation is more serious, indicating that a larger grain size gradient is more effective in inhibiting crack propagation. The introduction of gradient grain size promotes crack propagation and weakens the plasticity of the material relative to the nano-grained (NG) copper model.
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Two methylotrophic methanogens, designated strains FTZ2T and FTZ6T, were isolated from mangrove sediment sampled in Futian Mangrove Nature Reserve in Shenzhen, PR China. Cells of strains FTZ2T and FTZ6T were cocci, with diameters of 0.6-1.0 µm and 0.6-0.9 µm, respectively. Both strains grew on methanol, methylamine, dimethylamine and trimethylamine, but not on acetate, formate, H2/CO2, choline, betaine or dimethyl sulphide. Strain FTZ2T grew at 10-37â°C (optimally at 33â°C), pH 5.5-8.0 (optimally at pH 7.0) and 0-1.03 M NaCl (optimally at 0.17 M NaCl). In contrast, strain FTZ6T grew at 15-42â°C (optimally at 37â°C), pH 5.0-7.5 (optimally pH 6.5) and 0-1.03 M NaCl (optimally at 0.17 M NaCl). Both strains required magnesium for growth and were susceptible to sodium dodecyl sulphate. Biotin was required for the growth of strain FTZ2T but not of strain FTZ6T. The genomic G+C contents of strains FTZ2T and FTZ6T were 41.6 and 40.9âmol%, respectively. Phylogenetic analyses revealed that strain FTZ2T was mostly related to Methanolobus psychrotolerans YSF-03T, with 16S rRNA gene similarity of 98.6â%, an average nucleotide identity (ANI) of 82.5â%, and a digital DNA-DNA hybridization (dDDH) of 24.6â%. While strain FTZ6T was mostly related to Methanolobus vulcani PL-12/MT, with 16S rRNA gene similarity of 99.4â%, an ANI of 88.6% and a dDDH of 34.6â%. Based on phenotypic, phylogenetic and genotypic evidence, two novel species of the genus Methanolobus, Methanolobus mangrovi sp. nov. and Methanolobus sediminis sp. nov., are proposed. The type strain of M. mangrovi sp. nov. is FTZ2T (=CCAM 1276T=JCM 39396T) and the type strain of M. sediminis sp. nov. is FTZ6T (=CCAM 1277T=JCM 39397T).
Subject(s)
Fatty Acids , Sodium Chloride , Phylogeny , RNA, Ribosomal, 16S/genetics , Fatty Acids/chemistry , Sequence Analysis, DNA , Base Composition , DNA, Bacterial/genetics , Bacterial Typing Techniques , China , Methanosarcinaceae , Phospholipids/chemistryABSTRACT
A circumferential shear horizontal (CSH) guide wave-detection method using a periodic permanent magnet electromagnetic acoustic transducer (PPM EMAT) was proposed to solve the defect detection located at the inside of the pipe welded by supporting structures. Firstly, a low-frequency CSH0 mode was selected to establish a three-dimensional equivalent model for the defect detection to cross the pipe support, and the ability of the CSH0 guided wave to propagate through the support and weld structure was analyzed. Then, an experiment was used for the further exploration of the influence of different sizes and types of defects on detection after using the support, as well as the ability of detection mechanism to cross different pipe structures. The results show that both the experiment and the simulation received a good detection signal at 3 mm crack defects, which proves that the method can detect the defects by crossing the welded supporting structure. At the same time, the support structure shows a greater impact on the detection of small defects than the welded structure. The research in this paper can provide ideas for guide wave detection across the support structure in the future.
Subject(s)
Acoustics , Biological Products , Computer Simulation , TransducersABSTRACT
Methanothrix is widely distributed in natural and artificial anoxic environments and plays a major role in global methane emissions. It is one of only two genera that can form methane from acetate dismutation and through participation in direct interspecies electron transfer (DIET) with exoelectrogens. Although Methanothrix is a significant member of many methanogenic communities, little is known about its physiology. In this study, transcriptomics helped to identify potential routes of electron transfer during DIET between Geobacter metallireducens and Methanothrix thermoacetophila. Additions of magnetite to cultures significantly enhanced growth by acetoclastic methanogenesis and by DIET, while granular activated carbon (GAC) amendments impaired growth. Transcriptomics suggested that the OmaF-OmbF-OmcF porin complex and the octaheme outer membrane c-type cytochrome encoded by Gmet_0930, were important for electron transport across the outer membrane of G. metallireducens during DIET with Mx. thermoacetophila. Clear differences in the metabolism of Mx. thermoacetophila when grown via DIET or acetate dismutation were not apparent. However, genes coding for proteins involved in carbon fixation, the sheath fiber protein MspA, and a surface-associated quinoprotein, SqpA, were highly expressed in all conditions. Expression of gas vesicle genes was significantly lower in DIET- than acetate-grown cells, possibly to facilitate better contact between membrane-associated redox proteins during DIET. These studies reveal potential electron transfer mechanisms utilized by both Geobacter and Methanothrix during DIET and provide important insights into the physiology of Methanothrix in anoxic environments. IMPORTANCE Methanothrix is a significant methane producer in a variety of methanogenic environments including soils and sediments as well as anaerobic digesters. Its abundance in these anoxic environments has mostly been attributed to its high affinity for acetate and its ability to grow by acetoclastic methanogenesis. However, Methanothrix species can also generate methane by directly accepting electrons from exoelectrogenic bacteria through direct interspecies electron transfer (DIET). Methane production through DIET is likely to further increase their contribution to methane production in natural and artificial environments. Therefore, acquiring a better understanding of DIET with Methanothrix will help shed light on ways to (i) minimize microbial methane production in natural terrestrial environments and (ii) maximize biogas formation by anaerobic digesters treating waste.
Subject(s)
Geobacter , Electron Transport , Geobacter/metabolism , Electrons , Methanosarcinaceae/metabolism , Methane/metabolism , Acetates/metabolism , AnaerobiosisABSTRACT
The crack propagation mechanism of Cu nanowires is investigated by using molecular dynamics methods. The microstructural evolution of crack propagation at different strain rates and crack depths is analyzed. Meanwhile, the stress intensity factor at the crack tip during crack propagation is calculated to describe the crack propagation process of Cu nanowires under each condition. The simulation results show that the competition between lattice recovery and dislocation multiplication determines the crack propagation mode. Lattice recovery dominates the plastic deformation of Cu nanowires at low strain rates, and the crack propagation mode is shear fracture. With the increase in strain rate, the plastic deformation mechanism gradually changes from lattice recovery to dislocation multiplication, which makes the crack propagation change from shear fracture to ductile fracture. Interestingly, the crack propagation mechanism varies with crack depth. The deeper the preset crack of Cu nanowires, the weaker the deformation resistance, and the more likely the crack propagation is accompanied.
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Obesity has become a major public health problem worldwide and its occurrence is increasing globally. Obesity has also been shown to be involved in the occurrence and development of many diseases and pathological conditions, such as nonalcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus (T2DM), insulin resistance (IR). In recent years, gut microbiota has received extensive attention as an important regulatory part involved in host diseases and health status. A growing body of evidence suggests that gut microbiota dysbiosis has a significant adverse effect on the host. Small intestinal bacterial overgrowth (SIBO), a type of intestinal microbial dysbiosis, has been gradually revealed to be associated with obesity and its related diseases. The presence of SIBO may lead to the destruction of intestinal barrier integrity, increased intestinal permeability, increased endotoxin levels, activation of inflammatory responses, and translocation of bacteria from the colon to the small intestine. However, the causal relationship between SIBO and obesity and the specific mechanisms have not been well elucidated. This review discusses the cross-talk between SIBO and obesity and its related diseases, and expounds its potential mechanisms and interventions, which may help to discover new therapeutic targets for obesity and its related diseases and develop treatment options.
Subject(s)
Diabetes Mellitus, Type 2 , Non-alcoholic Fatty Liver Disease , Humans , Dysbiosis/complications , Obesity/complications , Non-alcoholic Fatty Liver Disease/drug therapy , Intestines/microbiologyABSTRACT
"Psychrodesulfovibrio", a proposed genus within the family Desulfovibrionaceae, is a group of sulfate-reducing bacteria with biogeochemical significance but restricted child taxa availability. In this study, a strictly anaerobic bacterium, designed strain FT415T, was isolated from mangrove sediments in Futian Mangrove Nature Reserve in Shenzhen, China. The strain was Gram-stain-negative, motile, and vibrio-shaped with a single polar flagellum, which grew at the temperature range of 15-42 °C (optimum 37 °C), pH range of 6.0-7.5 (optimum 6.8), and in the presence of 0-36 g l-1 NaCl (optimum 6 g l-1 NaCl). In the presence of sulfate, electron donors including lactate, ethanol, pyruvate, malate, fumarate, succinate, cysteine, and glycerol were incompletely oxidized to acetate, and H2 and formate were used as electron donors with acetate as the carbon source by strain FT415T. Sulfate, thiosulfate, sulfide, and anthraquinone-2,6-disulfonate were reduced in the presence of lactate. Fe(III) oxide was reduced without cell growth. Fermentative growth was observed with pyruvate and cysteine. Vitamins were not required for growth. The major cellular fatty acids (> 10%) were C16:0, summed feature 10 (C18:1 c11/t9/t6 and/or unknown ECL 17.834), C16:1 cis 9, and C18:0. The major polar lipids were phosphatidylethanolamine, phospholipids, and aminolipids. The predominant menaquinone was MK-6(H2). The genomic DNA G+C content was 56.7%. Phylogenetic analysis showed that strain FT415T shared a 98.1% similarity in 16S rRNA gene sequence, an average nucleotide identity value of 84.0%, an average amino-acid identity value of 85.4%, and a digital DNA-DNA hybridization value of 25.7% with its closest relative Desulfovibrio subterraneus HN2T, which has been proposed to be transferred to the genus "Psychrodesulfovibrio". Based on phenotypic, phylogenetic, and genotypic evidence, a new species of the family Desulfovibrionaceae, Desulfovibrio mangrovi sp. nov. was proposed with the type strain FT415T (=GDMCC 1.3410T=KCTC 25525T).
Subject(s)
Desulfovibrio , Sulfates , Humans , Child , Sulfates/analysis , Sulfates/metabolism , Phylogeny , RNA, Ribosomal, 16S/genetics , Base Composition , Cysteine/genetics , Sodium Chloride , Ferric Compounds , Sequence Analysis, DNA , Fatty Acids/analysis , Phospholipids/analysis , Lactates , Pyruvates , DNA, Bacterial/genetics , DNA, Bacterial/chemistry , Bacterial Typing Techniques , Geologic Sediments/microbiologyABSTRACT
In high-temperature environments, the signal-to-noise ratio (SNR) of the signal measured by electromagnetic acoustic transducers (EMAT) is low, and the signal characteristics are difficult to extract, which greatly affects their application in practical industry. Aiming at this problem, this paper proposes the least mean square adaptive filtering interpolation denoising method based on variational modal decomposition (AFIV). Firstly, the high-temperature EMAT signal was decomposed by variational modal decomposition (VMD). Then the high-frequency and low-frequency noises in the signal were filtered according to the excitation center frequency. Following the wavelet threshold denoising (WTD) for the noise component after VMD decomposition was carried out. Afterward, the noise component and signal component were connected by an adaptive filtering process to achieve further noise reduction. Finally, cubic spline interpolation was used to smooth the noise reduction curve and obtain the time information. To verify the effectiveness of the proposed method, it was applied to two kinds of ultrasonic signals from 25 to 700 °C. Compared with VMD, WTD, and empirical mode decomposition denoising, the SNR was increased by 2 times. The results show that this method can better extract the effective information of echo signals and realize the online thickness measurement at high temperature.
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BACKGROUND: Climate change caused by greenhouse gas emission has become a global hot topic. Although biotechnology is considered as an environmentally friendly method to produce chemicals, almost all biochemicals face carbon dioxide emission from inevitable respiration and energy metabolism of most microorganisms. To cater for the broad prospect of biochemicals, bioprocess optimization of diverse valuable products is becoming increasingly important for environmental sustainability and cleaner production. Based on Ca(OH)2 as a CO2 capture agent and pH regulator, a bioprocess was proposed for co-production of 1,3-propanediol (1,3-PDO), biohydrogen and micro-nano CaCO3 by Clostridium butyricum DL07. RESULTS: In fed-batch fermentation, the maximum concentration of 1,3-PDO reached up to 88.6 g/L with an overall productivity of 5.54 g/L/h. This productivity is 31.9% higher than the highest value previously reports (4.20 g/L/h). In addition, the ratio of H2 to CO2 in exhaust gas showed a remarkable 152-fold increase in the 5 M Ca(OH)2 group compared to 5 M NaOH as the CO2 capture agent. Green hydrogen in exhaust gas ranged between 17.2% and 20.2%, with the remainder being N2 with negligible CO2 emissions. During CO2 capture in situ, micro-nano calcite particles of CaCO3 with sizes in the range of 300 nm to 20 µm were formed simultaneously. Moreover, when compared with 5M NaOH group, the concentrations of soluble salts and proteins in the fermentation broth of 5 M Ca(OH)2 group were notably reduced by 53.6% and 44.1%, respectively. The remarkable reduction of soluble salts and proteins would contribute to the separation of 1,3-PDO. CONCLUSIONS: Ca(OH)2 was used as a CO2 capture agent and pH regulator in this study to promote the production of 1,3-PDO. Meanwhile, micro-nano CaCO3 and green H2 were co-produced. In addition, the soluble salts and proteins in the fermentation broth were significantly reduced.
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Temperature has a great influence on the mechanical properties of nano-materials. The molecular dynamics method was used to study the effect of temperature on the tension-compression asymmetry and Bauschinger effect of nano single crystal aluminum (NSCA). The strain-hardening behavior of NSCA in the tensile plastic stage is significantly enhanced when the temperature is higher than 400 K. The plastic deformation mechanism of tensile loading shifts from slip blocking of dislocations in grains to dislocation nucleation. The degradation of the mechanical properties of NSCA under compressive loading increases gradually with the increase of temperature. Dislocation emission is limited under compressive loading. Nonetheless, plastic deformation may still be regulated by dislocation slip during severe plastic deformation stages and at elevated temperatures. Temperature enhancement can effectively promote the movement of pre-dislocations and eliminate residual stresses. A new microscopic insight into the temperature attenuated Bauschinger effect is provided. This study provides important theoretical guidance for a comprehensive and in-depth understanding of the high-temperature mechanical properties and microstructure evolution mechanism of NSCA.
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The tremendous acoustic impedance difference between the piezoelectric composite and air prevents the ultrasonic transition, resulting in low amplitude for the received signal for the composite defect detection using an air-coupled transducer. The matching system, which includes the matching layers and bonding layers attached to the piezoelectric composite, can reduce the acoustic impedance difference and benefit the acoustic transition. In this paper, the fabrication method and modeling for the matching layers are proposed to optimize the transducer performance. The effects of bonding layer material on the transducer performance are also discussed. Experiments were conducted for modeling validation. The proposed model can predict the matching layer acoustic properties with an error of less than 11%. The bonding layer using the same material as the first matching layer can help to increase the sensitivity by about 33% compared to the traditional epoxy bonding. The optimized air-coupled ultrasonic transducer, based on the results of this study, has a 1283 mV amplitude in the air, which is 56% higher than commercially available transducers, and can identify the defects in two typical non-metallic composite materials easily.
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Dynamic cardiac magnetic resonance imaging (CMRI) is an important tool for the non-invasive assessment of cardiovascular disease. However, dynamic CMRI suffers from long acquisition times due to the need of obtaining images with high temporal and spatial resolution, whole-heart coverage. Conventionally, a multidimensional dataset in dynamic CMRI is treated as a series of two-dimensional matrices, and then various matrix/vector transforms are used to explore the sparsity of MR images. In this paper, we propose a low-rank tensor coding (LRTC) model with tensor sparsity for the application of compressive sensing (CS) in dynamic CMRI. In this framework, each group of 3D similar patches extracted from high-dimensional images is considered to be a low-rank tensor. LRTC can better capture the sparse part of dynamic CMRI and make full use of the redundancy between the feature vectors of adjacent positions. ADMM technique is introduced to tackle the proposed model, where soft threshold operator is used to solving the l1 norm relaxation. Higher-order singular value decomposition (HOSVD) is exploited to process high-dimensional tensors and mine correlations in space-time dimensions. Validations based on cardiac cine and myocardial perfusion datasets indicate that the proposed method achieved comparable reconstruction accuracy with the low-rank matrix recovery methods, and outperformed the conventional sparse recovery methods.
Subject(s)
Algorithms , Data Compression , Heart/diagnostic imaging , Magnetic Resonance Imaging/methods , RadiographyABSTRACT
Direct interspecies electron transfer (DIET) may be most important in methanogenic environments, but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor. To better understand DIET with methanogens, the transcriptome of Geobacter metallireducens during DIET-based growth with G. sulfurreducens reducing fumarate was compared with G. metallireducens grown in coculture with diverse Methanosarcina. The transcriptome of G. metallireducens cocultured with G. sulfurreducens was significantly different from those with Methanosarcina. Furthermore, the transcriptome of G. metallireducens grown with Methanosarcina barkeri, which lacks outer-surface c-type cytochromes, differed from those of G. metallireducens cocultured with M. acetivorans or M. subterranea, which have an outer-surface c-type cytochrome that serves as an electrical connect for DIET. Differences in G. metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable. Cocultures with c-type cytochrome deletion mutant strains, ∆Gmet_0930, ∆Gmet_0557 and ∆Gmet_2896, never became established with G. sulfurreducens but adapted to grow with all three Methanosarcina. Two porin-cytochrome complexes, PccF and PccG, were important for DIET; however, PccG was more important for growth with Methanosarcina. Unlike cocultures with G. sulfurreducens and M. acetivorans, electrically conductive pili were not needed for growth with M. barkeri. Shewanella oneidensis, another electroactive microbe with abundant outer-surface c-type cytochromes, did not grow via DIET. The results demonstrate that the presence of outer-surface c-type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron-accepting partner on the physiology of the electron-donating DIET partner.
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Methane-producing microorganisms accelerate the corrosion of iron-containing metals. Previous studies have inferred that some methanogens might directly accept electrons from Fe(0), but when this possibility was more intensively investigated, H2 was shown to be an intermediary electron carrier between Fe(0) and methanogens. Here, we report that Methanosarcina acetivorans catalyzes direct metal-to-microbe electron transfer to support methane production. Deletion of the gene for the multiheme, outer-surface c-type cytochrome MmcA eliminated methane production from Fe(0), consistent with the key role of MmcA in other forms of extracellular electron exchange. These findings, coupled with the previous demonstration that outer-surface c-type cytochromes are also electrical contacts for electron uptake from Fe(0) by Geobacter and Shewanella species, suggest that the presence of multiheme c-type cytochromes on corrosion surfaces might be diagnostic for direct metal-to-microbe electron transfer and that interfering with cytochrome function might be a strategy to mitigate corrosion.
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Nickel-based single crystal alloys have excellent mechanical properties due to its unique two-phase structure and interface. Therefore, molecular dynamics methods were used to simulate nanoindentation and microstructural evolution. We found the indenter reaction force and hardness of the Ni3Al phase is the largest. The pop-in event in Ni3Al phase is more obvious than that in the Ni phase and Ni/Ni3Al phase. Because lots of dislocations in the Ni3Al phase break through the barrier of the interface and cut into the Ni phase, while dislocations in the Ni phase only slip inside the Ni phase. Moreover, we found that the position of the starting point of the adhesion force recovery is mainly related to the elastic recovery of the material. The stronger the elastic recovery of the phase, the smaller the depth value corresponding to the starting point of the recovery. We further studied the variation of potential energy with indentation depth and found that the change of wave trough of the load-displacement (P-h) curve is related to stacking fault energy. This study has important theoretical guiding significance for the in-depth understanding and engineering application of the mechanical properties of nickel-based single crystal alloys.
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Direct interspecies electron transfer (DIET) between bacteria and methanogenic archaea appears to be an important syntrophy in both natural and engineered methanogenic environments. However, the electrical connections on the outer surface of methanogens and the subsequent processing of electrons for carbon dioxide reduction to methane are poorly understood. Here, we report that the genetically tractable methanogen Methanosarcina acetivorans can grow via DIET in coculture with Geobacter metallireducens serving as the electron-donating partner. Comparison of gene expression patterns in M. acetivorans grown in coculture versus pure-culture growth on acetate revealed that transcripts for the outer-surface multiheme c-type cytochrome MmcA were higher during DIET-based growth. Deletion of mmcA inhibited DIET. The high aromatic amino acid content of M. acetivorans archaellins suggests that they might assemble into electrically conductive archaella. A mutant that could not express archaella was deficient in DIET. However, this mutant grew in DIET-based coculture as well as the archaellum-expressing parental strain in the presence of granular activated carbon, which was previously shown to serve as a substitute for electrically conductive pili as a conduit for long-range interspecies electron transfer in other DIET-based cocultures. Transcriptomic data suggesting that the membrane-bound Rnf, Fpo, and HdrED complexes also play a role in DIET were incorporated into a charge-balanced model illustrating how electrons entering the cell through MmcA can yield energy to support growth from carbon dioxide reduction. The results are the first genetics-based functional demonstration of likely outer-surface electrical contacts for DIET in a methanogen. IMPORTANCE The conversion of organic matter to methane plays an important role in the global carbon cycle and is an effective strategy for converting wastes to a useful biofuel. The reduction of carbon dioxide to methane accounts for approximately a third of the methane produced in anaerobic soils and sediments as well as waste digesters. Potential electron donors for carbon dioxide reduction are H2 or electrons derived from direct interspecies electron transfer (DIET) between bacteria and methanogens. Elucidating the relative importance of these electron donors has been difficult due to a lack of information on the electrical connections on the outer surfaces of methanogens and how they process the electrons received from DIET. Transcriptomic patterns and gene deletion phenotypes reported here provide insight into how a group of Methanosarcina organisms that play an important role in methane production in soils and sediments participate in DIET.
Subject(s)
Methanosarcina/metabolism , Archaeal Proteins/genetics , Archaeal Proteins/metabolism , Electron Transport , Electrons , Methane/metabolism , Methanosarcina/genetics , Methanosarcina/growth & development , TranscriptomeABSTRACT
Vascular calcification is a major risk factor for cardiovascular disease and accounts for a large proportion of deaths from cardiovascular disease in patients with chronic kidney disease. The high incidence, rapid progression and irreversibility of vascular smooth muscle cell (VSMC) calcification in patients has attracted attention. In the present study, the effect of intermedin147 (IMD147), an important isoform of intermedin, was investigated on the calcification of rat cardiovascular VSMCs induced by high phosphate (HP). To stimulate osteoblastlike differentiation and calcification in rat VSMCs, 10 mM ßsodium glycerophosphate was used. The VSMCs were then treated with three doses of IMD147 and the effects of IMD147 on VSMC calcification, on the expression of osteogenic markers [osteoprotegerin, Runtrelated transcription factor 2 (Runx2) and osteopontin (OPN)] and on alkaline phosphatase (ALP) activity were assessed. HP treatment significantly enhanced the cellular calcium content of VSMCs, the expression of osteogenic markers, and ALP activity, while IMD147 significantly reversed these effects in a dosedependent manner. The protein expression levels of Wnt1, Wnt3a and active ßcatenin were determined and it was found that IMD147 significantly inhibited their expression. Following ßcatenin silencing, the protein expression levels Runx2 and OPN were increased compared with the IMD147 treatment alone, indicating a role for the Wnt/ßcatenin pathway in the effects of IMD147 on osteogenic markers. The present study suggested that IMD147 inhibited HPinduced VSMC calcification by regulating the Wnt/ßcatenin signaling pathway.