In the present investigation, functionally continuous graded AA 7075 Al/SiC composites (Al-6.5%SiC and Al-9.5%SiC) were processed through the centrifugal casting technique. Additionally, the as cast ...AA 7075 alloy was prepared for comparison purposes. The wear, hardness, strength and micro structure properties were characterized for the alloy and composites. The composites show clearly smooth and uniform SiC particles gradient from the core to the surface. The density of the composites decreases with the increasing particle volume fraction due to the increased defects. The improvement of hardness and wear resistance from the core to the surface of the FG composites is in accordance with the increasing amount of the particles. The wear rate of the FG composites increases with the increasing sliding speed, load and sliding distance conditions. Among the as cast alloy and the composites, the FG Al-9.5%SiC composite is found to be superior in terms of hardness and wear resistance. At low sliding speed (2 m/s) and load (15 N) conditions, the abrasive wear and matrix cracking are found to be dominant in contrast to the complex interaction of multi mode wear mechanisms such as tribo-oxidation, abrasive and delamination wear exist at higher load and speed conditions.
The elite Indian rice variety, Naveen is highly susceptible to major biotic and abiotic stresses such as blast, bacterial blight (BB), gall midge (GM) and drought which limit its productivity in ...rainfed areas. In the present study, a combined approach of marker-assisted forward (MAFB) and back cross (MABC) breeding was followed to introgress three major genes, viz., Pi9 for blast, Xa21 for bacterial blight (BB), and Gm8 for gall midge (GM) and three major QTLs, viz., qDTY.sub.1.1, qDTY.sub.2.2 and qDTY.sub.4.1 conferring increased yield under drought in the background of Naveen. At each stage of advancement, gene-based/linked markers were used for the foreground selection of biotic and abiotic stress tolerant genes/QTLs. Intensive phenotype-based selections were performed in the field for identification of lines with high level of resistance against blast, BB, GM and drought tolerance without yield penalty under non-stress situation. A set of 8 MAFB lines and 12 MABC lines with 3 to 6 genes/QTLs and possessing resistance/tolerance against biotic stresses and reproductive stage drought stress with better yield performance compared to Naveen were developed. Lines developed through combined MAFB and MABC performed better than lines developed only through MAFB. This study exemplifies the utility of the combined approach of marker-assisted forward and backcrosses breeding for targeted improvement of multiple biotic and abiotic stress resistance in the background of popular mega varieties.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Reactive stromal cells are an integral part of tumor microenvironment (TME) and interact with cancer cells to regulate their growth. Although targeting stromal cells could be a viable therapy to ...regulate the communication between TME and cancer cells, identification of stromal targets that make cancer cells vulnerable has remained challenging and elusive. Here, we identify a previously unrecognized mechanism whereby metabolism of reactive stromal cells is reprogrammed through an upregulated glutamine anabolic pathway. This dysfunctional stromal metabolism confers atypical metabolic flexibility and adaptive mechanisms in stromal cells, allowing them to harness carbon and nitrogen from noncanonical sources to synthesize glutamine in nutrient-deprived conditions existing in TME. Using an orthotopic mouse model for ovarian carcinoma, we find that co-targeting glutamine synthetase in stroma and glutaminase in cancer cells reduces tumor weight, nodules, and metastasis. We present a synthetic lethal approach to target tumor stroma and cancer cells simultaneously for desirable therapeutic outcomes.
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•CAFs have an upregulated glutamine anabolic pathway compared to NOFs•CAFs harness atypical carbon and nitrogen sources for glutamine synthesis•Crosstalk between stromal-epithelial cells augments dysregulated metabolism in CAFs•Targeting stromal GS in an orthotopic ovarian cancer model induces tumor regression
Yang et al. reveal that cancer-associated fibroblasts boost glutamine production by harnessing carbon and nitrogen from atypical nutrient sources to maintain cancer cell growth when glutamine is scarce. Co-targeting stromal glutamine synthetase and cancer cell glutaminase disrupts this metabolic crosstalk, inducing tumor regression in an ovarian carcinoma mouse model.
The increased occurrence and severity of drought stress have led to a high yield decline in rice in recent years in drought-affected areas. Drought research at the International Rice Research ...Institute (IRRI) over the past decade has concentrated on direct selection for grain yield under drought. This approach has led to the successful development and release of 17 high-yielding drought-tolerant rice varieties in South Asia, Southeast Asia, and Africa. In addition to this, 14 quantitative trait loci (QTLs) showing a large effect against high-yielding drought-susceptible popular varieties were identified using grain yield as a selection criterion. Six of these (qDTY1.1, qDTY2.2, qDTY3.1, qDTY3.2, qDTY6.1, and qDTY12.1) showed an effect against two or more high-yielding genetic backgrounds in both the lowland and upland ecosystem, indicating their usefulness in increasing the grain yield of rice under drought. The yield of popular rice varieties IR64 and Vandana has been successfully improved through a well-planned marker-assisted backcross breeding approach, and QTL introgression in several other popular varieties is in progress. The identification of large-effect QTLs for grain yield under drought and the higher yield increase under drought obtained through the use of these QTLs (which has not been reported in other cereals) indicate that rice, because of its continuous cultivation in two diverse ecosystems (upland, drought tolerant, and lowland, drought susceptible), has benefited from the existence of larger genetic variability than in other cereals. This can be successfully exploited using marker-assisted breeding.
The present work investigates comprehensively the tribological behaviour of WC-Cr3C2-Ni coatings prepared by atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) spray methods. The dry ...sliding wear at room and elevated temperature (up to 800 °C), wet (oil-based fracturing fluid) sliding wear at room temperature were studied against an alumina ball using the ball-on-disc tribometer according to the ASTM G99 standard. The erosion wear was studied using air-jet erosion tester (ASTM G76) at the impact angles 30° and 90° and temperatures 500 °C and 650 °C. The HVOF coating showed higher hardness, dense morphological structure and a lower degree of decarburisation as compared to APS coating. The HVOF coating offers better wear resistance over the APS coating under both dry and wet sliding conditions. Significant improvement in the wear resistance, especially above 500 °C is attributed to the uniform formation of lubricious WO3. The solid particle erosion resistance of both coatings is observed to be the same up to 650 °C under 30° and 90° impact angles.
•HVOF coating has better wear resistance under dry and wet sliding conditions.•Lubricious tribo-film controls the wear under high-temperature in both coatings.•Higher erosion resistance of HVOF coating than APS coating•Higher wear in APS coating due to more decarburization, lower hardness and interlamellar cohesion
In this paper, we study the wear resistance of multi-layered composites of Cu/SiC + Gr hybrid composites prepared by layer compaction and pressure sintering. The tribological behavior and wear ...resistance of the composites were evaluated at a range of sliding speeds (5, 10, 30 and 35m/s) in a laboratory scale inertia brake dynamometer for brake friction material applications. The wear surface morphology and mechanisms were studied using scanning electron microscopy (SEM), XRD, and stereoscopy. The microstructure of the composites was also characterized using SEM and optical microscopy and the mechanical response in compression and flexure was evaluated. The results of these tests indicate that the density, wear resistance, braking behavior and mechanical response can be significantly improved by the presence of a layer of copper away from the sliding surface. The presence of the layer also improved friction and wear resistance significantly. The formation of mechanically mixed tribolayer and oxides (Fe3O4) reduced the wear rate and stabilized the friction coefficient at 30 and 35m/s. Finally, crack deflection and branching at the interface between the composite and Cu layers improved the flexural strength of the layered composites. The fractography analysis indicates a quasi-cleavage intergranular fracture in the composite layer and a purely ductile fracture in the Cu layer.
•Studied wear and mechanical properties of multilayer Cu/SiC/graphite composites.•Microstructure characterization confirms the sound quality of layers in the composites.•Multilayer composites show improved friction and wear, and mechanical properties.•Crack deflection and branching in the MMCs show the improved crack resistance properties.
Cancer-associated fibroblasts (CAFs) are a major cellular component of tumor microenvironment in most solid cancers. Altered cellular metabolism is a hallmark of cancer, and much of the published ...literature has focused on neoplastic cell-autonomous processes for these adaptations. We demonstrate that exosomes secreted by patient-derived CAFs can strikingly reprogram the metabolic machinery following their uptake by cancer cells. We find that CAF-derived exosomes (CDEs) inhibit mitochondrial oxidative phosphorylation, thereby increasing glycolysis and glutamine-dependent reductive carboxylation in cancer cells. Through 13C-labeled isotope labeling experiments we elucidate that exosomes supply amino acids to nutrient-deprived cancer cells in a mechanism similar to macropinocytosis, albeit without the previously described dependence on oncogenic-Kras signaling. Using intra-exosomal metabolomics, we provide compelling evidence that CDEs contain intact metabolites, including amino acids, lipids, and TCA-cycle intermediates that are avidly utilized by cancer cells for central carbon metabolism and promoting tumor growth under nutrient deprivation or nutrient stressed conditions.
In this work we investigated the friction and wear properties of Fe/SiC/graphite hybrid composites using a sub-scale dynamometer disk brake testing system. Two particle size ranges (1–30μm and ...150–180μm) and three particle volume fractions (10%, 15% and 20%) of SiC were considered. The sliding speed conditions considered in this study (25–35m/s) were comparable to that experienced by brake materials in high speed braking applications in aircrafts, race car and high speed trains. We examined the effect of coating the SiC particles with BaSO4 to improve interfacial properties and prevent potential undesirable interfacial reactions. The wear loss was found to decrease with increasing volume fraction of SiC for all particulate sizes. At low sliding speeds the composites with large particle sizes and high volume fractions were found to be more effective in controlling wear. On the other hand, at higher sliding speeds the high volume fraction composites were found to be more effective in controlling wear for all particle sizes. This is attributed to a transition in the wear mechanism at higher sliding speeds.
•Studied wear properties of Fe/SiC particulate metal matrix composites.•Performed high sliding speed tests speeds for aircraft brake applications.•Tested a range of particle volume fractions, two particle sizes and three sliding speeds.•High volume fraction composites with small particle sizes were found to be most effective.
In this paper we studied the tribological behavior of iron matrix composites at high sliding speeds (25–35m/s) typical of aircraft braking conditions. We developed two types of Fe matrix composites ...with different elastic modulus reinforcements: silica (71GPa) and mullite (143GPa) particulates using powder metallurgy. Two different size ranges: large (150–250μm) and small sizes (1–10μm) and a range of volume fractions of the particulates were also considered. The dry sliding wear and braking performance of the composites were investigated using a sub-scale disc braking dynamometer. The wear tests of the composites show that large size and high volume fraction of reinforcement particles provides better wear resistance and braking performance at high sliding speed conditions (25m/s–35m/s) for both Fe/silica composites and Fe/mullite composites. Significantly, Fe/mullite composites at lower volume fractions showed greater wear resistance than the Fe/silica composites due to the higher elastic modulus of the mullite particles. A wear track examination of composites showed that different wear mechanisms were operative at the different speeds. Our results indicate that composites with a high volume fraction of large sized reinforcement particles of high elastic modulus are to be preferred for braking performance and low wear loss at high sliding speed applications.
•We studied wear properties of Fe/Sic particulate metal matrix composites.•High sliding speed tests for aircraft brake applications were conducted.•High volume fraction composites with large particle sizes were most effective.
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