A metastable β titanium alloy, Ti–2Al-9.2Mo–2Fe (wt.%), with athermal ω phase after quenching has been subjected to high strain rate (∼3000 s−1) compression at ambient temperature by Spilt Hopkinson ...Pressure Bar arrangement. Reverse β-to-ω transformation was investigated by transmission electron microscopy during deformation. Furthermore, the novel distribution of athermal ω phase in {332} twinning and stress-induced martensitic was observed. We reveal that such novel distribution is attributed to the influence of ω phase on {332} twinning and stress-induced martensite transformation (SIMT) based on the viewpoint of the instability of the lattice structure of metastable β phase. Furthermore, a new process of twinning and SIMT in current alloy with ω phase was proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK, ZAGLJ
The mechanical behavior of a metastable β titanium alloy, Ti-2Al-9.2Mo-2Fe (wt%), was studied through high compression strain rate (~3000 s−1) at ambient temperature by Spilt Hopkinson Pressure Bar ...(SHPB) tests after solution treatment at 850 ℃ for 0.5 h and 950 ℃ for 1 h. The mechanism of deformation and microstructure evolution was investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Multiple deformation mechanisms, including primary and secondary {332} twinning, stress-induced martensite, and stress-induced ω-phase and dislocation slips, were identified in specimens subjected to solution treatment at 850 ℃ for 0.5 h. In contrast, only primary and secondary {332} twinning and dislocation slips were detected in specimens subjected to solution treatment at 950 ℃ for 1 h. The athermal ω precipitation produced after solution treatment and elevated temperature generated during dynamic loading played a crucial role in the different deformation mechanisms observed in the two different specimens. Moreover, the deformation mechanisms active during plastic deformation in the different strain regimes affected the development of different textures in the Ti-2Al-9.2Mo-2Fe alloys from each regime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK, ZAGLJ
Summary
Extracellular signals are the key components of microbial cell–cell communication systems. This report identified a diffusible signal factor (DSF), which regulates virulence in Xanthomonas ...campestris pv. campestris, as cis‐11‐methyl‐2‐dodecenoic acid, an α,β unsaturated fatty acid. Analysis of DSF derivatives established the double bond at the α,β positions as the most important structural feature for DSF biological activity. A range of bacterial pathogens, including several Mycobacterium species, also displayed DSF‐like activity. Furthermore, DSF is structurally and functionally related to farnesoic acid (FA), which regulates morphological transition and virulence by Candida albicans, a fungal pathogen. Similar to FA, which is also an α,β unsaturated fatty acid, DSF inhibits the dimorphic transition of C. albicans at a physiologically relevant concentration. We conclude that α,β unsaturated fatty acids represent a new class of extracellular signals for bacterial and fungal cell–cell communications. As prokaryote–eukaryote interactions are ubiquitous, such cross‐kingdom conservation in cell–cell communication systems might have significant ecological and economic importance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Trimethylamine N-oxide (TMAO), choline and betaine serum levels have been associated with metabolic diseases including type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). These ...associations could be mediated by insulin resistance. However, the relationships among these metabolites, insulin resistance and NAFLD have not been thoroughly investigated. Moreover, it has recently been suggested that TMAO could play a role in NAFLD by altering bile acid metabolism. We examined the association between circulating TMAO, choline and betaine levels and NAFLD in obese subjects.
Serum TMAO, choline, betaine and bile acid levels were measured in 357 Mexican obese patients with different grades of NAFLD as determined by liver histology. Associations of NAFLD with TMAO, choline and betaine levels were tested. Moreover, association of TMAO levels with non-alcoholic steatohepatitis (NASH) was tested separately in patients with and without T2D.
TMAO and choline levels were significantly associated with NAFLD histologic features and NASH risk. While increased serum TMAO levels were significantly associated with NASH in patients with T2D, in non-T2D subjects this association lost significance after adjusting for sex, BMI and HOMA2-IR. Moreover, circulating secondary bile acids were associated both with increased TMAO levels and NASH.
In obese patients, circulating TMAO levels were associated with NASH mainly in the presence of T2D. Functional studies are required to evaluate the role of insulin resistance and T2D in this association, both highly prevalent in NASH patients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of lamellar α phase (αL) thickness on tensile behavior at 700°C of BTi-6431S titanium alloy is investigated. Two types of bi-modal microstructures are introduced through different heat ...treatments. Both of them have similar volume fraction of equiaxed α phases (αe). One has thick α lamella named BTL, and another has fine α lamella named BFL. The results show that dynamic recrystallization (DRX) happens in the α phase during tensile process at 700°C. After being deformed at 700°C, the shape of αL in BFL and BTL transforms into sphere. BFL possesses higher tensile strength, and the elongation is twice as large as BTL at 700°C. Compared to the thick αL, the fine αL has more excellent accommodative deformation capability. There are cracks found to be of wedge type located at the grain triple junctions in both BFL and BTL. In addition, some small voids stay at the lamellar boundaries in BTL. In order to acquire a good combination of tensile strength and elongation at 700°C for BTi-6431S alloy, the thickness of αL should be reduced.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK
Electron backscattering diffraction technique and calculated Schmid factor presented in a spherical coordinate system were applied to investigate the twinning behavior of Gr2 purity Ti under both ...quasi-static and dynamic compressive deformation. Three twinning systems {101¯2}, {112¯2} and {112¯1} were identified. With the help of the calculated SF map, the corresponding critical resolved shear stress range was determined to be 321–361MPa, 367–393MPa and 525–538MPa. Moreover, strain rate was proved to have a minor effect on the value of CRSS of twinning.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK
Mechanical properties of compacted graphite iron (CGI) are substantially related to the microstructural contents and morphologies. To develop a simple and effective relation between graphite ...morphology and mechanical properties of CGI, a prediction method based on microstructual simulation is proposed in the present work. CGI slices are selected depicting the distribution of graphite spatial morphology. Tensile properties and damage mechanisms of microstructural slices are simulated with finite element (FE) method. By statistics of the graphite area fraction and vermicularity, it shows that 2D slicing scheme can reasonably depict the spatial morphology of 3D CGI microstructure. Tensile properties and damage mechanisms are further analyzed in slice results. A good agreement of the results is observed between experiment and simulation, which verifies the effectiveness of slice FE simulation. This research provides an effective way to estimate the mechanical properties of different regions in the large CGI components.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, UL, UM, UPCLJ, UPUK
Methods to predict the
S–
N curves of high-strength steels in the very high cycle fatigue (VHCF) regime are reviewed. At the same time, a new prediction in form of Basquin’s equation is proposed ...based on the prediction of fatigue strengths in both high cycle fatigue regime and very high cycle fatigue regime. The new prediction is compared to the prior predictions and experiments results obtained by our recent experiment and others’ published papers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The fatigue properties of four high strength steels with same strength class but containing different inclusion sizes were investigated using an ultrasonic fatigue testing machine in the gigacycle ...fatigue regime. The fracture surfaces were observed using field emission scanning electron microscopy (FESEM) and element distributions at the crack origins were measured by an electron probe microanalyzer (EPMA). The fatigue behavior can be divided into three categories:
(a)
The S–N curve displays a continuous decline and the internal cracks initiated from the large oxide inclusions for commercial 50CrV4 steel in which the average inclusion size is about 29
μm.
(b)
Step-wise S–N curves were observed for clean 54SiCrV6 and clean 50CrV4 steels in which the average inclusion sizes are about 3.0 and 2.4
μm respectively. Most fatigue failures originated from the VC inclusion clusters at the lower stress amplitudes.
(c)
For clean 54SiCr6 steel in which the inclusion size is smaller than 1
μm, the fatigue cracks did not initiated from inclusions or inclusion clusters but from the region enriched with carbon. S–N curve shows that the fatigue failure hardly occurs from 10
6 to 10
9 cycles, in other words, the fatigue reliability can be substantially improved in the super long fatigue life regime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Deficits in impulsivity and affect dysregulation are key features of attention-deficit/hyperactivity disorder (ADHD) besides impairing levels of hyperactivity and/or inattention. However, the neural ...substrates underlying these traits are relatively under-investigated. In this study, we use resting-state functional magnetic resonance imaging to test the hypothesis of diminished functional integration within the affective/limbic network (which includes the amygdala, hippocampus, subgenual cingulate cortex, orbitofrontal cortex and nucleus accumbens) of children with ADHD, which is associated with their behavioral measures of emotional control deficits. Resting state-fMRI data were obtained from 12 healthy control subjects and 15 children with ADHD, all who had a minimum one-month washout period for medications and supplements. Children with ADHD demonstrated less integrated affective network, evidenced by increased bilateral amygdalar and decreased left orbitofrontal connectivity within the affective network compared to healthy controls. The hyper-connectivity at the left amygdalar within the affective network was associated with increased aggressiveness and conduct problems, as well as decline in functioning in children with ADHD. Similar findings in affective network dysconnectivity were replicated in a subset of children with ADHD three months later. Our findings of divergent changes in amygdala and orbitofrontal intrinsic connectivity support the hypothesis of an impaired functional integration within the affective network in childhood ADHD. Larger prospective studies of the intrinsic affective network in ADHD are required, which may provide further insight on the biological mechanisms of emotional control deficits observed in ADHD.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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