A particulate reinforced magnesium matrix composite fabricated by stir casting was extruded at 250
°C with an extrusion ratio of 12:1 and constant RAM speed of 15
mm/s. Extrusion of the composite ...causes large scale dynamic recrystallization resulting in a fine matrix microstructure. The reinforcing particles stimulate dynamic recrystallization, and dynamic recrystallization in the composite is sensitive to the particle content on a local scale. The particle distribution of the composite before and after extrusion was studied using a window technique. It is found that the segregation of particles in the as-cast composite is largely eliminated by extrusion and the particle distribution is significantly improved. Extrusion-induced damage to the reinforcement is observed in the extruded composites, and the particle fracture induced by extrusion is also sensitive to the particle content on a local scale.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The fracture behavior of SiCp/AZ91 magnesium matrix composite fabricated by stir casting is investigated using the in situ SEM technique. Experimental results show that (1) the dominant microcrack ...nucleation mode is interface decohesion in particle-dense regions because of the weak interface formed during the solidification process of the composite and large stress concentrations caused by particle segregation, (2) microcracks coalesce by the failure of matrix ligaments between microcracks while additional microcracks are initiated in the particle-dense region ahead of the coalesced microcracks, and (3) cracks propagate by coalescence of microcracks or along the particle/matrix interface. And so we come to the conclusion that the fracture mechanism of SiCp/AZ91 composite is interface-controlled. The in situ SEM observations are verified by complementary SEM studies of the fractured specimens of conventional tensile tests. And so, the in situ SEM observations can be qualitative representation on the fracture behavior of bulk SiCp/AZ91 composite.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The microtubule-associated protein tau has risk alleles for both Alzheimer's disease and Parkinson's disease and mutations that cause brain degenerative diseases termed tauopathies. Aggregated tau ...forms neurofibrillary tangles in these pathologies, but little is certain about the function of tau or its mode of involvement in pathogenesis. Neuronal iron accumulation has been observed pathologically in the cortex in Alzheimer's disease, the substantia nigra (SN) in Parkinson's disease and various brain regions in the tauopathies. Here we report that tau-knockout mice develop age-dependent brain atrophy, iron accumulation and SN neuronal loss, with concomitant cognitive deficits and parkinsonism. These changes are prevented by oral treatment with a moderate iron chelator, clioquinol. Amyloid precursor protein (APP) ferroxidase activity couples with surface ferroportin to export iron, but its activity is inhibited in Alzheimer's disease, thereby causing neuronal iron accumulation. In primary neuronal culture, we found loss of tau also causes iron retention, by decreasing surface trafficking of APP. Soluble tau levels fall in affected brain regions in Alzheimer's disease and tauopathies, and we found a similar decrease of soluble tau in the SN in both Parkinson's disease and the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model. These data suggest that the loss of soluble tau could contribute to toxic neuronal iron accumulation in Alzheimer's disease, Parkinson's disease and tauopathies, and that it can be rescued pharmacologically.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Although hepatocellular carcinoma (HCC) is usually response to radiation therapy, radioresistance is still the major obstacle that limits the efficacy of radiotherapy for HCC patients. Therefore, ...further investigation of underlying mechanisms in radioresistant HCC cells is warranted. In this study, we determined the effect of early growth response factor (Egr-1) on irradiation-induced autophagy and radioresistance in HCC cell lines SMMC-7721 and HepG2. We showed that autophagy-related gene 4B (Atg4B) is induced by Egr-1 upon ionizing radiation (IR) in HCC cells. Luciferase reporter assays and chromatin immunoprecipitation (ChIP) revealed that Egr-1 binds to the Atg4B promoter to upregulate its expression in HCC cells. Suppression of Egr-1 function by dominant-negative Egr-1 dampens IR-induced autophagy, cell migration, and increases cell sensitivity to radiotherapy. Together, these results suggest that Egr-1 contributes to HCC radioresistance through directly upregulating target gene Atg4B, which may serve as a protective mechanism by preferential activation of the autophagy.
The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is a major pathogen of soybean (Glycine max L). Heterodera glycines continues to spread into new areas, with recent records from the ...province of Quebec, Canada. Until recently, H. glycines in China was restricted to two major soybean production areas North East and Huang-Huai-Hai. Over 1,000 soil samples from 16 provinces were collected and H. glycines cysts and second-stage juveniles (J2) were extracted from soil using the sieving-decanting method. To verify the identity of the sequences, sequenced products were subjected to a database search using BLAST. Sequences from the ITS and 28S region were 98 to 100% similar, respectively, to those of H. glycines GenBank accessions AY667456 (ITS) and DQ328692 (28S). Molecular analysis of ITS and 28S rRNA confirmed the identity as H. glycines. The identity of these populations as H. glycines was also demonstrated by species-specific sequence characterized amplified region (SCAR) primers.
PurposeThe purpose of this study is to simultaneously determine the constitutive parameters and boundary conditions by solving inverse mechanical problems of power hardening elastoplastic materials ...in three-dimensional geometries.Design/methodology/approachThe power hardening elastoplastic problem is solved by the complex variable finite element method in software ABAQUS, based on a three-dimensional complex stress element using user-defined element subroutine. The complex-variable-differentiation method is introduced and used to accurately calculate the sensitivity coefficients in the multiple parameters identification method, and the Levenberg–Marquardt algorithm is applied to carry out the inversion.FindingsNumerical results indicate that the complex variable finite element method has good performance for solving elastoplastic problems of three-dimensional geometries. The inversion method is effective and accurate for simultaneously identifying multi-parameters of power hardening elastoplastic problems in three-dimensional geometries, which could be employed for solving inverse elastoplastic problems in engineering applications.Originality/valueThe constitutive parameters and boundary conditions are simultaneously identified for power hardening elastoplastic problems in three-dimensional geometries, which is much challenging in practical applications. The numerical results show that the inversion method has high accuracy, good stability, and fast convergence speed.
Wang
R‐L,
Zeng
R‐S,
Peng
S‐L,
Chen
B‐M,
Liang X‐T & Xin X‐W (2011) Elevated temperature may accelerate invasive expansion of the liana plant Ipomoea cairica. Weed Research51, 574–580.
Summary
...Numerous studies have shown that elevated CO2 levels promote liana establishment in forests, thus suggesting their increased prevalence in the future in these habitats. Limited information exists, however, concerning the effects of potentially increasing global temperatures on these plants. The invasive liana Ipomoea cairica has infested many forests in South China. We hypothesised that elevated temperature could change the resource allocation pattern and allelopathic potential of this plant, resulting in increased invasiveness. We compared seed germination, growth rates and leachate phytotoxicity of I. cairica at three temperatures (22, 26 and 30°C). The seed germination rates of I. cairica were 11.6%, 21.2% and 26.4% at 22, 26 and 30°C respectively. Elevated temperature resulted in significant changes in morphology and biomass allocation of I. cairica. Shoot biomass of the plant increased, while the root biomass decreased with increasing temperature. Phytotoxicity of aqueous leachates from fresh leaves of I. cairica varied depending on receptor plants, but showed the strongest phytotoxic effects at the highest temperature (30°C). Our results provide key information concerning the effects of elevated temperatures on the allelopathic potential, germination and growth of I. cairica and indicate that global warming could increase the invasiveness of this species.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
A novel bulk Mg-Gd matrix nanocomposite reinforced with GdN nanoparticles has been successfully fabricated utilizing an advanced powder metallurgy route within in-situ reactions during sintering ...process. The as-prepared nanocomposite with nanocrystalline (NC) or ultrafine-grained (UFG) matrix and homogeneously dispersed nanoparticles exhibits phenomenal mechanical properties: ultimate tensile strength (UTS) of 521MPa, yield strength (YS) of 506MPa and tensile elongation (El) of 2.8%. The drastic improvement of the strength in comparison with that of conventional magnesium alloys is ascribed to fine grain strengthening of NC/UFG matrix, dispersion strengthening and load bearing mechanism of the GdN nanoparticles and β (Mg5Gd) or β′ (Mg3Gd) precipitates.
•A novel bulk GdN /Mg-Gd nanocomposite was successfully fabricated.•GdN nanoparticles synthesized by in-situ reaction were distributed homogeneously.•The GdN/Mg-Gd nanocomposite exhibits phenomenal mechanical properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Low temperature affects plant growth and biomass accumulation in the Qinghai-Tibet Plateau.
Bacillus
is an important plant growth-promoting rhizobacteria that can promote plant growth directly or ...indirectly. In this study, bacteria suspensions (cell concentration 1 × 10
7
cfu/mL) of
Bacillus amyloliquefaciens
strain GL18 were interacted with
Avena sativa
seedlings by the root irrigation method under 4°C low-temperature conditions. The biomass accumulation, as well as the physiological and biochemical activities of
A. sativa
, was detected over 14 days. The results showed that the plant height, root length, fresh and dry weight of
A. sativa
treated at 4°C with
B. amyloliquefaciens
by root irrigation increased by 39.28, 32.50, 114.89, and 87.17%, respectively, compared to untreated control. The levels of plant hormones such as abscisic acid, salicylic acid and jasmonic acid were significantly increased, and the activities of superoxide dismutase, peroxidase and catalase increased rapidly and then decreased slowly. The accumulation of hydrogen peroxide and malondialdehyde decreased, and the contents of proline and betaine increased significantly. The genome of GL18 strain was sequenced and its related functional genes were analyzed. The results showed that genome of GL18 strain contained gene clusters encoding proteins related to the synthesis of lipopeptide compounds such as surfactin, iturin, and fengycin, encoding genes involved in 3-indole acetic acid synthesis as well as genes related to the synthesis of plant growth-promoting substances such as siderophore and polyamines. This study provided experimental data and a theoretical basis for the manner in which
Bacillus
promotes the growth of
A
.
sativa
under low-temperature stress.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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