Low Stress Research Articles

Response and Resilience of Carbon Nanotube Micropillars to Shear Flow.

Interactions between carbon nanotubes and fluid flows are central to the operation of several emerging nanotechnologies. In this paper, we explore the fluid-structure interaction of carbon nanotube micropillars in wall-bounded shear flows, relevant to recently developed microscale wall shear stress sensors. We monitor the deformation of carbon nanotube micropillars in channel flow as the flow rate and wall shear stress are gradually varied. We quantify how the micropillars bend at low wall shear stress, and then will commonly tilt abruptly from their base above a threshold wall shear stress, which is attributed to the lower density of the micropillars in this region. Some micropillars are observed to flutter rapidly between a vertical and horizontal position around this threshold wall shear stress, before settling to a tilted position as wall shear stress increases further. Tilted micropillars are found to kink sharply near their base, similar to the observed buckling near the base of carbon nanotube micropillars in compression. Upon reducing the flow rate, micropillars are found to fully recover from a near horizontal position to a near vertical position, even with repeated on-off cycling. At sufficiently high wall shear stress, the micropillars were found to detach at the catalyst particle-substrate interface. The mechanical response of carbon nanotube micropillars in airflow revealed by this study provides a basis for future development efforts and the accurate simulation of carbon nanotube micropillar wall shear stress sensors.&#xD.

Computational model-based hemodynamic comparisons of traditional and modified idealized models of autologous radiocephalic fistula.

Autologous arteriovenous fistula (AVF) is a commonly used vascular access (VA) for hemodialysis, and hemodynamic changes are one of the main factors for its failure. To explore the effect of geometry on the hemodynamics in the AVF, a modified model is built with a gradual and smooth turn at the anastomosis and is compared with the traditional model, which has an abrupt sharp turn at the anastomisis. Transient computational fluid dynamics (CFD) simulations were performed for the comparison and analysis of the hemodynamic fields of the two models at different stages of the pulse cycle. The results showed that the low shear stress region and high oscillatory shear stress region in the modified AVF model coincided with regions of intimal hyperplasia that have been identified by previous studies. A comparison with the blood flow velocities measured in vivo was performed, and the error between the simulation results and the medical data was reduced by 22% in the modified model, which verifies the rationality and utility of the modified model.

Design Factors of Ti-Base Abutments Related to the Biomechanics Behavior of Dental Implant Prostheses: Finite Element Analysis and Validation via In Vitro Load Creeping Tests

This study has been carried out to analyze the influence of the design of three geometric elements (wall thickness, platform width, and chamfer) of Ti-base abutments on the distribution of stresses and strains on the implant, the retention screw, the Ti base, and the bone. This study was carried out using FEA, analyzing eight different Ti-base models based on combinations of the geometric factors under study. The model was adapted to the standard Dynamic Loading Test For Endosseous Dental Implants. A force of 360 N with a direction of 30° was simulated and the maximum load values were calculated for each model, which are related to a result higher than the proportional elastic limit of the implant. The transferred stresses according to von Mises and microdeformations were measured for all the alloplastic elements and the simulated support bone, respectively. These results were validated with a static load test using a creep testing machine. The results show that the design factors involved with the most appropriate stress distribution are the chamfer, a thick wall, and a narrow platform. A greater thickness (0.4 mm) is also related to lower stress values according to von Mises at the level of the retaining screws. In general, the distributions of tension at the implants and microdeformation at the level of the cortical and trabecular bone are similar in all study models. The in vitro study on a Ti-base control model determined that the maximum load before the mechanical failure of the implant is 360 N, in accordance with the results obtained for all the Ti-base designs analyzed in the FEA. The results of this FEA study show that modifications to the Ti-base design influence the biomechanical behavior and, ultimately, the way in which tension is transferred to the entire prosthesis–implant–bone system.

Students with prior anatomy experience start out stronger in medical school gross anatomy.

Gross anatomy is a crucial course in medical school; it sets the foundation for future coursework and is highly valued by clinicians. While both medical students and faculty recognize the importance of pre-medical school anatomy experience, few medical schools require it as a prerequisite. Consequently, medical school gross anatomy courses have a diverse range of prior anatomy experience among students. Prior studies have shown mixed results regarding the impact of pre-medical school anatomy experience on medical school gross anatomy performance, often using final exam scores as the metric of analysis. In this study, we investigated the relationship between pre-medical school anatomy experience and medical school gross anatomy performance among students at New York Institute of Technology, College of Osteopathic Medicine. We surveyed students from all four matriculated years and analyzed their individual anatomy laboratory exam scores and final anatomy laboratory course scores. We found that students with prior anatomy experience performed significantly better on the first anatomy laboratory exam, leading to an overall positive effect on their final anatomy laboratory score. However, this advantage seemed to diminish in subsequent exams, suggesting that students without prior experience rapidly adjusted to the course challenges. Students with prior anatomy experience felt more prepared for the anatomy course, reported lower stress levels, and believed they had an advantage over peers without prior experience. Our study highlights the importance of pre-medical school anatomy experience, particularly for early performance in the anatomy course.

The duration of priming, elimination and maintenance of low temperature stress memory response to periodic chilling risk in pepper (Capsicum annuum L.)

Pepper (Capsicum annuum L.) as often out-of-season vegetable is cultivated in greenhouse along with the large difference between night and day. To cope with repeated and frequent low temperature stress, pepper often adopt a memory response by remembering one past recurring stress, and enable survival of a harsher chilling stress that may arise later. Here, we wanted to determine how continuous and intermittent low temperature stress affect the priming and elimination of low temperature memory of pepper plants, as well as the response to subsequent stress and their capacity to remember low temperature information. The results showed that the continuous low temperature induced the priming of low temperature memory and improved cold resistance of pepper, and the storage of low temperature information in pepper plants could be maintained for at least 12 h, but not longer than 36 h. The results of rewarming for 3–5 d after 3 d of low temperature priming at 5 °C and then triggering low temperature stimulus for 1–2 d showed that rewarming for 3 d to trigger the stimulus again could still prime the low temperature memory, but the duration of low temperature memory was almost completely eliminated after rewarming for 5 d. Our study also unveiled that low temperature memory of pepper continued for 3–4 d under low temperature stress. Overall, these findings unraveled that the priming, elimination and maintenance of low temperature memory was associated with the duration of low temperature treatment and rewarming, and the low temperature memory in pepper was not enhanced with the extension of low temperature treatment, but the low temperature memory in pepper would be completely eliminated with the extension of rewarming.

Biomechanical analysis of stabilization for thoracolumbar anterior spinal failure caused by osteolytic lesions, a finite element comparison of direct lateral corpectomy and posterior long segment instrumentation

Background ContextOsteolytic lesions caused by infection or metastatic disease of the spine can induce instability. Different surgical strategies are available to restore stability in this scenario, however little is known how various reconstruction techniques affect spinal biomechanics. PurposeTo analyze and quantify the biomechanical effects of three different surgical reconstruction techniques in the treatment of a T12 osteolytic model. Study Design/SettingFinite element analysis of the thoracic spine with a T12 osteolytic lesion. MethodsUsing CT scans from a 20-year-old man without structural deformity, simulation of an osteolytic lesion with a 50% defect at the posterior aspect of T12 vertebral body (anterior? Posterior? Be specific) was created. (was the defect created by the force? Or was the force then delivered after the defect was created?) by a 490 N vertical force to T9. Next, three common instrumentation techniques treating the osteolytic lesion were modeled and biomechanically tested. These included: Model A, corpectomy with short segment fixation (T11-L1) and two long-segment instrumentations; Model B long segment fixation with triple rod construct; Model C long segment fixation with dual rod construct. A load of 480N was then applied on the spine models in vertically downward direction on T9. Von Mises stresses were measured (MPa) in the discs, vertebrae, and implants. ResultsModel A demonstrated the lowest stress on construct material, adjacent vertebral bodies, and discs but increased stress on the instrumented vertebrae. Model B was more rigid and demonstrated lower construct stress compared to Model C. However, Model C had the lowest vertebral body stress in flexion, extension, and lateral bending in the most upper instrumented vertebral body, but the highest screw pull-out stress when compared to Model A and Model B. ConclusionsThis osteolytic T12 model provides unique biomechanical data that can help to tailor surgical strategies in select scenarios. While optimal outcomes are best achieved with a construct tailored to a specific patient's need for stabilization, our findings can be generalized for instances of cancerous lesions, low bone density, and infectious causes. Clinical RelevanceThe results of this study can help with the choice of appropriate surgical reconstruction technique based on patient-specific characteristics.

Biomechanical analysis of patient specific cone vs conventional stem in revision total knee arthroplasty

BackgroundIn revision total knee arthroplasty, addressing significant bone loss often involves the use of cemented or press-fit stems to ensure implant stability and long-term fixation. A possible alternative to stem was recently introduced utilizing custom-made porous metaphyseal cones, designed to reconstruct the missing tibial and femoral geometries. Early clinical and radiological assessments have shown promising results. The objective of this research was to biomechanically evaluate the performances of these custom-made cones.MethodsThe biomechanical study was conducted using a validated finite element model. The bone geometries of a patient (selected for their history of four knee revisions due to infection and periprosthetic fractures, followed by a successful treatment with custom-made 3D-printed metaphyseal cones) were employed for the study. On these bone models, different revision scenarios were simulated and examined biomechanically: (A) custom-made cementless metaphyseal cones; (B) cemented stems; (C) press-fit stems; (D) distal femoral reconstruction with press-fit stem. All the models were analyzed at 0 °and 90 °of flexion, under physiological load conditions simulating daily activities; stress distribution, average Von-Mises stresses and risk of fracture were then analyzed and compared among configurations.ResultsThe use of custom-made 3D-printed cones exhibited the most favorable stress distribution in both femoral and tibial bones. Tibial bone stress was evenly distributed in custom-made cone configurations, while stress concentration was observed in distal regions for the other scenarios. Additionally, custom-made cones displayed overall homogeneity and lower stress levels, potentially contributing to limit pain. Symmetrical stress distribution was observed between the lateral and medial proximal tibia in custom-made cone models, whereas other scenarios exhibited uneven stress, particularly in the anterior tibial bone.ConclusionsThe biomechanical analysis of porous custom-made metaphyseal cones in re-revision arthroplasties is in agreement with the positive clinical and radiological outcomes. These findings provide valuable insights into the potential benefits of using custom-made cones, which offer more uniform stress distribution and may contribute to improve patient outcomes in revision TKA procedures. Further studies in this direction are warranted to validate these biomechanical findings.

Effects of Double-sided Textures Matching on Friction and Wear Performance in Reciprocating Contact Interface

With increasing demands for friction reduction and wear resistance in heavy-duty diesel engines, the design of surface textures in reciprocating contact zone of the cylinder liner and piston ring (CLPR) has been a major concern. Through designed orthogonal tests for optimizing the double-sided textured CLPR, a maximum reduction in the friction coefficient of 12.63% was achieved for the superior double-sided textured CLPR compared to the untextured surface, with corresponding reductions in the wear depth of the cylinder liner and piston ring of 16.73% and 18.25%, respectively. The relative position variation between the CLPR microtextures at the sliding contact area caused different stress values and stress distribution. Compared to the inferior double-sided textured CLPR, superior double-sided textured CLPR with lower stress concentration and symmetrical distribution within the contact area generated smoother and flatter worn platforms and non-spalling dimple edges with less abrasive wear. It can provide some insight into the matching design of double-sided CLPR surfaces under heavy load conditions.

Nonlinear network connectedness: Assessing financial risk transmission in MENA and influence of external financial conditions

This study investigates the influence of global financial market conditions on financial risk connectedness and transmission among the Middle East and North Africa (MENA) economies. Utilizing weekly realized stock market volatilities as a measure of risk and employing a smooth transition threshold vector autoregressive (STVAR) model to analyze risk transmission under varying levels of financial stress, the authors also examine the impact of external macroeconomic conditions on the risk connectedness of MENA economies. The results indicate that the overall connectedness, based on a standard VAR model, is moderate at 48.34%. However, in the low financial stress regime, overall connectedness increases to 52.79%, and in the high financial stress regime, it rises to 72.94%, indicating stronger risk interdependency among MENA countries during times of high stress. In the high financial stress regime, Kuwait, Oman, Qatar, Saudi Arabia, Turkey, and the United Arab Emirates are identified as net risk transmitters among MENA countries. The study also reveals that risk transmission across MENA is more pronounced in the regime-dependent model compared to the overall mean-based VAR model.

A new single magnetic core coupled-inductor based active switched Quasi Z-source inverter

This paper presents a novel topology for Z-source inverters (ZSI). The new Z-Source network is based on the coupled-inductors and active switched boost. Features of the topology include high voltage boost ability, single magnetic-core, low voltage stress on the active switch, and capacitors. The principles of operation, analysis, voltage and current equations of each component, and the converter voltage gain in the steady-state are presented. A comparison with other topologies has also been performed to determine the advantages and disadvantages of the proposed ZSI. Finally, experimental results of the laboratory prototype are presented to confirm the performance of the proposed topology.

Differential responses of bell pepper genotypes to indigenous Pseudomonas putida A32 treatment: implications for drought resilience.

This study aimed to evaluate the potential of endophytic plant growth-promoting bacteria (PGPB), Pseudomonas putida A32, to mitigate drought stress in two bell pepper genotypes, Amfora 19 and Amfora 26, and to assess the genotype-specific responses to bacterial treatment. The isolate P. putida A32 was selected for its remarkable beneficial properties, exhibiting 13 out of 14 traits tested. Under drought conditions, Amfora 26 showed increased relative water content (RWC) and decreased H2O2 and malondialdehyde following bacterial treatment, while Amfora 19 exhibited enhanced growth parameters but responded less to bacterial treatment regarding drought parameters. However, Amfora 19 displayed inherent drought tolerance mechanisms, as indicated by lower stress parameters compared to Amfora 26. The study emphasises the importance of genotype-specific responses to PGPB treatment and the mechanisms of drought tolerance in peppers. P. putida A32 effectively mitigated drought stress in both genotypes, with differential responses influenced by plant genotype. Our study confirmed our initial hypothesis that Amfora 19, as a genotype tolerant to biotic stress, is also more tolerant to abiotic stress. Understanding these interactions is crucial for the development of customised strategies to improve plant productivity and tolerance to drought.

Fulvic acid application increases rice seedlings performance under low phosphorus stress

BackgroundFulvic acid enhances plant growth and interacts synergistically with phosphate fertilizer to alleviate the agricultural production problem of low phosphorus fertilizer utilization efficiency. However, the underlying mechanism of its action remains poorly understood. In this study, we investigated the impact of fulvic acid application with varying concentrations (0, 40, 60, 80 and 120 mg/L) on rice performance in plants grown in a hydroponic system subjected to low phosphorus stress. The rice growth phenotypes, biomass, root morphology, phosphorus uptake, and the impact of fulvic acid on the rhizosphere environment of rice, were assessed.ResultsThe findings showed that adding appropriate concentrations of exogenous fulvic acid could promote the growth performance of rice under low phosphorus stress. Particularly at T1 (40 mg/L) and T2 (60 mg/L) over the control effectively increased rice biomass by 25.42% and 24.56%, respectively. Fulvic acid treatments stimulated root morphogenesis, up-regulated phosphate transporter genes, and facilitated phosphorus absorption and accumulation. Especially T1 (20.52%), T2 (18.10%) and T3 (20.48%) treatments significantly increased phosphorus uptake in rice, thereby alleviating low phosphorus stress. Additionally, fulvic acid elevated organic acids concentration in roots and up-regulated plasma membrane H+-ATPase genes, promoting organic acids secretion. This metabolic alteration can also alleviate low phosphorus stress in rice.ConclusionsThe effect of exogenous fulvic acid on physiological indicators is concentration-dependent under low phosphorus stress, enhances rice performance and reduces reliance on phosphorus fertilizer. This provides new insights to shed light on the mechanism of alleviating low phosphorus stress in rice through fulvic acid application, an eco-friendly tool.

Low salinity stress increases the risk of Vibrio parahaemolyticus infection and gut microbiota dysbiosis in Pacific white shrimp

BackgroundExtreme precipitation events often cause sudden drops in salinity, leading to disease outbreaks in shrimp aquaculture. Evidence suggests that environmental stress increases animal host susceptibility to pathogens. However, the mechanisms of how low salinity stress induces disease susceptibility remain poorly understood.MethodsWe investigated the acute response of shrimp gut microbiota exposed to pathogens under low salinity stress. For comparison, shrimp were exposed to Vibrio infection under two salinity conditions: optimal salinity (Control group) and low salinity stress (Stress group). High throughput 16S rRNA sequencing and real-time PCR were employed to characterize the shrimp gut microbiota and quantify the severity level of Vibrio infection.ResultsThe results showed that low salinity stress increased Vibrio infection levels, reduced gut microbiota species richness, and perturbed microbial functions in the shrimp gut, leading to significant changes in lipopolysaccharide biosynthesis that promoted the growth of pathogens. Gut microbiota of the bacterial genera Candidatus Bacilliplasma, Cellvibrio, and Photobacterium were identified as biomarkers of the Stress group. The functions of the gut microbiota in the Stress group were primarily associated with cellular processes and the metabolism of lipid-related compounds.ConclusionsOur findings reveal how environmental stress, particularly low salinity, increases shrimp susceptibility to Vibrio infection by affecting the gut microbiota. This highlights the importance of avoiding low salinity stress and promoting gut microbiota resilience to maintain the health of shrimp.

High nitrite accumulation in hydrogenotrophic denitrification at low temperature: Transcriptional regulation and microbial community succession

High Pressure Hydrogenotrophic Denitrification (HPHD) provided a promising alternative for efficient and clean nitrate removal. In particular, the denitrification rates at low temperature could be compensated by elevated H2 partial pressure. However, nitrite reduction was strongly inhibited while nitrate reduction was barely affected at low temperature. In this study, the nitrate reduction gradually recovered under long-term low temperature stress, while nitrite accumulation increased from 0.1 to 41.0 mg N/L. The activities of the electron transport system (ETS), nitrate reductase (NAR), and nitrite reductase (NIR) decreased by 45.8 %, 27.3 %, and 39.3 %, respectively, as the temperature dropped from 30 °C to 15 °C. Real time quantitative PCR analysis revealed that the denitrifying gene expression rather than gene abundance regulated nitrogen biotransformation. The substantial nitrite accumulation was attributed to the significant up-regulation by 54.7 % of narG gene expression and down-regulation by 73.7 % of nirS gene expression in hydrogenotrophic denitrifiers. In addition, the nirS-gene-bearing denitrifiers were more sensitive to low temperature compared to those bearing nirK gene. The dominant populations shifted from the genera Paracoccus to Hydrogenophaga under long-term low temperature stress. Overall, this study revealed the microbial mechanism of high nitrite accumulation in hydrogenotrophic denitrification at low temperature.

The mechanism of low strain rate and moderate principal stress effects in triaxial prestressed marble under lateral impulsive load

Stress waves have a significant impact on the strength and deformation characteristics of deep rock masses at a certain distance from the epicenter or explosion source. In order to study the dynamic responses of deep-buried marble under the disturbance condition, the true triaxial compression test (TTC), the true triaxial disturbed compression test with lateral impulsive load (TTDC) and the synchronous acoustic emission monitoring on the marble were respectively conducted to simulate the influencing process of the seismic wave. The test results show that under lateral impulsive load, a ‘short-range plateau’ phenomenon occurs in the stress-strain curves of the marble samples. With the increase of intermediate principal stress σ2, the ‘short-range plateau’ of ε2 and ε3 curves gradually shrinks and even disappears, and the anisotropy of sample deformation becomes more obvious. The σ2 significantly affects the microfracture activity and the evolution of energy inside the samples under the impulsive load in the whole process of true triaxial disturbed compression. The lateral impulsive load weakens the marble strength which shows an obvious low strain-rate disturbance effect. The marble samples under the impulsive load have a high sensitivity to axial load and are liable to form local brittle fracture. This fracture induced by local stress concentration and strain energy release becomes more pronounced when the axial load is further applied to the samples. By contrast, the impulsive load in σ2 direction has a protective effect on limiting the lateral deformation of the samples and improving its axial deformation capacity, which greatly changes the action mechanism of σ2 on the sample lateral deformation. The variation of marble mechanical properties under lateral impulsive load is the result of the interaction between the low strain-rate disturbance and the intermediate principal stress effect.

Numerical assessment of thermal insulation and stress responses in film-cooled turbine vane thermal barrier coatings under CMAS deposition conditions

Deposition of CaO-MgO-Al2O3-SiO2 (CMAS) significantly contributes to the spalling of thermal barrier coatings (TBCs) on turbine vanes. A thorough understanding of the thermodynamic properties during CMAS deposition is critical for advancing the lifetime design of TBCs. This study employs the CMAS gas thermal shock test to determine the deposition characteristics, which were then analyzed using the critical velocity model. The results of this analysis align closely with experimental outcomes. Based on the numerical simulation of the fluid-solid coupling method, we further explored the insulation efficiency and stress distribution in TBCs under CMAS deposition conditions. It was observed that CMAS predominantly accumulates on the pressure side and within the film pores of the vane TBCs, with minimal deposition on the suction side. Such deposition patterns result in an increased overall temperature of the vane, concurrently diminishing the TBCs' insulation efficiency. Specifically, CMAS deposition raised the maximum surface temperature of the vane by 100 K and decreased the peak insulation performance of the TBCs by 16 %. Additionally, the deposition induced higher stresses within both the TBCs and the underlying vane substrate, with a 7 % increase in the maximum principal stresses at the TBC surface and a 6 % increase in the substrate. Consequently, under CMAS deposition conditions, TBCs in regions of low insulation efficiency and high stress on turbine vanes are prone to cracking and subsequent spallation.

Effect of taurine on growth and immune response of Pacific white shrimp (Litopenaeus vannamei) cultured at different temperatures

Low temperature is a common challenge in the culture of Pacific white shrimp (Litopenaeus vannamei), and taurine is a potential nutrient that may improve its cold-resistance. This experiment aimed to investigate effects of dietary taurine on growth and immune response of Pacific white shrimp cultured at normal and cold temperatures. Six diets were supplemented with increasing levels of taurine (0, 0.2, 0.4, 0.6, 0.8 and 1.0%) and fed to shrimp (1.59 ± 0.03 g) reared at two water temperatures (28 °C and 20 °C) for 8 weeks. The results showed that compared with 28 °C, shrimp reared at 20 °C showed lower growth performance, feed utilization, apparent digestibility and total hemocyte count (THC) (P < 0.05), but higher content of serum glucose, intracellular reactive oxygen species (ROS) and Ca2+, malonaldehyde (MDA) and apoptosis rate (P < 0.05), indicating a higher risk of oxidative damage during low temperature stress. Interestingly, shrimp could cope with cold stress by changing hemocyte composition, increasing antioxidant enzyme activity and genes expression of apoptosis and autophagy. The effect of taurine was different at different temperatures. At 28 °C, taurine supplementation improved growth rate of shrimp by increasing digestive enzyme activities, digestion absorption rate and nutrient utilization. Based on the quadratic model of weight gain rate, feed efficiency, protein retention efficiency and the broken line model of apparent digestibility coefficients of protein, the amount of taurine required for shrimp reared at 28 °C was 0.57–0.60% of dry diet. At 20 °C, taurine increased the number of THC, granulocytes, semi-granulocytes, the activities of antioxidant enzymes such as superoxide dismutase and catalase, and decreased the content of ROS in the cells, which may enhance cold resistance of shrimp. Moreover, taurine supplementation down-regulated mRNA expression of cell apoptosis genes (cyt-c, caspase-9 and caspase-3) and up-regulated mRNA expression of cell autophagy genes (atg1, atg13, atg7 and lc3) (P < 0.05), which may help to maintain cell stability at 20 °C. The optimal requirement of taurine in shrimp reared at 20 °C was 0.56–0.66% of dry diet in this experiment based on THC and MDA content. In conclusion, our study suggests that appropriate taurine promotes growth and feed utilization at optimal temperature and enhances the stability of hemocyte at low temperature in white shrimp.

An ecotype-specific effect of osmopriming and melatonin during salt stress in Arabidopsis thaliana

BackgroundNatural populations of Arabidopsis thaliana exhibit phenotypic variations in specific environments and growth conditions. However, this variation has not been explored after seed osmopriming treatments. The natural variation in biomass production and root system architecture (RSA) was investigated across the Arabidopsis thaliana core collection in response to the pre-sawing seed treatments by osmopriming, with and without melatonin (Mel). The goal was to identify and characterize physiologically contrasting ecotypes.ResultsVariability in RSA parameters in response to PEG-6000 seed osmopriming with and without Mel was observed across Arabidopsis thaliana ecotypes with especially positive impact of Mel addition under both control and 100 mM NaCl stress conditions. Two ecotypes, Can-0 and Kn-0, exhibited contrasted root phenotypes: seed osmopriming with and without Mel reduced the root growth of Can-0 plants while enhancing it in Kn-0 ones under both control and salt stress conditions. To understand the stress responses in these two ecotypes, main stress markers as well as physiological analyses were assessed in shoots and roots. Although the effect of Mel addition was evident in both ecotypes, its protective effect was more pronounced in Kn-0. Antioxidant enzymes were induced by osmopriming with Mel in both ecotypes, but Kn-0 was characterized by a higher responsiveness, especially in the activities of peroxidases in roots. Kn-0 plants experienced lower oxidative stress, and salt-induced ROS accumulation was reduced by osmopriming with Mel. In contrast, Can-0 exhibited lower enzyme activities but the accumulation of proline in its organs was particularly high. In both ecotypes, a greater response of antioxidant enzymes and proline accumulation was observed compared to mechanisms involving the reduction of Na+ content and prevention of K+ efflux.ConclusionsIn contrast to Can-0, Kn-0 plants grown from seeds osmoprimed with and without Mel displayed a lower root sensitivity to NaCl-induced oxidative stress. The opposite root growth patterns, enhanced by osmopriming treatments might result from different protective mechanisms employed by these two ecotypes which in turn result from adaptive strategies proper to specific habitats from which Can-0 and Kn-0 originate. The isolation of contrasting phenotypes paves the way for the identification of genetic factors affecting osmopriming efficiency.

Recoverable and plastic strains generated by forward and reverse martensitic transformations under external stress in NiTi SMA wires

Although superelastic NiTi shape memory alloy wire displays very high resistance to plastic deformation in austenite and martensite phases, incremental plastic strains are recorded whenever the cubic to monoclinic martensitic transformation (MT) proceeds under external stress leading to functional fatigue degradation. Therefore, special closed-loop thermomechanical loading tests were performed to shed light on the mechanism by which the incremental plastic strain are generated. These tests revealed that both forward and reverse MTs occurring above certain stress thresholds generate plastic strains specific for the [temperature, stress] conditions under which the MTs occurred. While the forward MT upon cooling does not produce plastic strain or permanent lattice defects up to 500 MPa stress, the reverse MT upon heating starts to generate them from 100 MPa. While plastic strain generated by the forward MT merely elongates the wire, plastic strain generated by the reverse MT also reduces the recoverable strain. Since the reverse MT upon heating generates plastic strains at lower external stresses than the forward MT upon cooling, it is largely responsible for cyclic instability of NiTi actuators. The characteristic thresholds and magnitudes of plastic strains generated by the forward and reverse MTs define the functional fatigue limits for specific NiTi wires.

Mining key genes associated with phosphorus deficiency through genome-wide identification and characterization of cucumber SPX family genes

BackgroundProteins harboring the SPX domain are crucial for the regulation of phosphate (Pi) homeostasis in plants. This study aimed to identify and analyze the entire SPX gene family within the cucumber genome.ResultsThe cucumber genome encompassed 16 SPX domain-containing genes, which were distributed across six chromosomes and categorized into four distinct subfamilies: SPX, SPX-MFS, SPX-EXS and SPX-RING, based on their structure characteristics. Additionally, gene duplications and synteny analysis were conducted for CsSPXs, revealing that their promoter regions were enriched with a variety of hormone-responsive, biotic/abiotic stress and typical P1BS-related elements. Tissue expression profiling of CsSPX genes revealed that certain members were specifically expressed in particular organs, suggesting essential roles in cucumber growth and development. Under low Pi stress, CsSPX1 and CsSPX2 exhibited a particularly strong response to Pi starvation. It was observed that the cucumber cultivar Xintaimici displayed greater tolerance to low Pi compared to black-spined cucumber under low Pi stress conditions. Protein interaction networks for the 16 CsSPX proteins were predicted, and yeast two-hybrid assay revealed that CsPHR1 interacted with CsSPX2, CsSPX3, CsSPX4 and CsSPX5, implying their involvement in the Pi signaling pathway in conjunction with CsPHR1.ConclusionThis research lays the foundation for further exploration of the function of the CsSPX genes in response to low Pi stress and for elucidating the underlying mechanism.