•Short fatigue crack growth behaviours in Inconel 718 were studied at room temperature.•Residual stress fields were induced by indentation procedures.•Short fatigue crack growth can be described ...fully by a closure concept.•The influence by compressive residual stress field cannot be appropriately estimated by Kr.
The effects of compressive residual stress on short fatigue crack growth in Inconel 718 have been investigated. Using two different indentation procedures, controlled plane-strain compressive residual stress fields were applied to short through-thickness cracks, which had been generated by machining away wakes of long cracks that had been grown down to threshold levels at a stress ratio of 0.1. Short fatigue crack growth tests were conducted at stress ratios of 0.1 and 0.7. At a stress ratio of 0.1, the residual stress-free testpieces demonstrated typical short fatigue crack growth behaviour, indicated by a reduction of threshold value and increases in fatigue crack growth rates compared to those of long fatigue cracks. A significant decrease in short crack growth rates was observed within the compressive residual stress region of indented testpieces, together with an increase of threshold values. At a high stress ratio of 0.7, any similar decrease in rate is barely observable. This indicates that the effects of compressive residual stress on short fatigue crack growth are monotonic in sign and could perhaps be simulated by a crack closure approach similar to that applied for long fatigue cracks. However the superposition principle which incorporates the compressive residual stress as a negative stress intensity factor, despite many successful applications to long fatigue cracks, is found to be inappropriate here. Hence one should be cautious when extending such a methodology to short fatigue cracks as it may result in optimistic life estimations.
Ca
-activated K
channels are critical to cellular Ca
homeostasis and excitability; they couple intracellular Ca
and membrane voltage change. Of these, the small, 4-14 pS, conductance SK channels ...include three,
encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC
∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca
overload and reactive oxygen species generation. SK channels show low voltage but marked Ca
dependences (EC
∼ 300-500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca
channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
The present study investigates the induction of axon and myelin remodeling as a possible mechanism by which treatment of stroke with bone marrow stromal cells improves neurological functional ...recovery. Adult male Wistar rats were subjected to 2 h of middle cerebral artery occlusion, followed by an injection of 2×10
6 rat bone marrow stromal cells or phosphate-buffered saline into the internal carotid artery 24 h later. Animals were killed at 28 days after stroke. Functional tests, histo- and immunohistochemical staining were performed. Significant functional recovery was found after bone marrow stromal cell administration in all the three tests performed (modified neurological severity score, adhesive-removal and corner tests). Bone marrow stromal cell treatment markedly increased vessel sprouting, synaptophysin expression and NG2 positive cell numbers and density in the cortical peri-infarct area. In bone marrow stromal cell-treated rats, the number of Ki-67 positive proliferating cells and oligodendrocyte precursor cells in the corpus callosum increased significantly in concert with the enhancement of the areas of the corpus callosum in both hemispheres. These results suggest that bone marrow stromal cells facilitate axonal sprouting and remyelination in the cortical ischemic boundary zone and corpus callosum, which may underlie neurological functional improvement caused by bone marrow stromal cell treatment.
We applied ozone source apportionment technology (OSAT) with tagged tracers coupled within the Comprehensive Air Quality Model with Extensions (CAMx) to study the region and source category ...contribution to surface ozone in the Yangtze River Delta area in summer of 2013. Results indicate that the daytime ozone concentrations in the YRD region are influenced by emissions both locally, regionally and super-regionally. At urban Shanghai, Hangzhou and Suzhou receptors, the ozone formation is mainly VOC-limited, precursor emissions form Zhejiang province dominate their O3 concentrations. At the junction area among two provinces and Shanghai city, the ozone is usually influenced by all the three areas. The daily max O3 at the Dianshan Lake in July are contributed by Zhejiang (48.5%), Jiangsu (11.7%), Anhui (11.6%) and Shanghai (7.4%), long-range transport constitutes around 20.9%. At Chongming site, the BVOC emissions rate is higher than urban region. Regional contribution results show that Shanghai constitutes 15.6%, Jiangsu contributes 16.2% and Zhejiang accounts for 25.5% of the daily max O3. The analysis of the source category contribution to high ozone in the Yangtze River Delta region indicates that the most significant anthropogenic emission source sectors contributing to O3 pollution include industry, vehicle exhaust, although the effects vary with source sector and selected pollution episodes. Emissions of NOx and VOCs emitted from the fuel combustion of industrial boilers and kilns, together with VOCs emissions from industrial process contribute a lot to the high concentrations in urban Hangzhou, Suzhou and Shanghai. The contribution from regional elevated power plants cannot be neglected, especially to Dianshan Lake. Fugitive emissions of volatile pollution sources also have certain contribution to regional O3. These results indicate that the regional collaboration is of most importance to reduce ambient ozone pollution, particularly during high ozone episodes.
•A high O3 episode over the YRD was simulated using the CAMx modeling system.•Ozone source apportionment technology was applied to study the formation mechanism and sources of O3.•Contributions of different source regions and source categories to O3 were analyzed.
Recovery in soil properties and processes after sand burial in the Tengger Desert, northern China, was documented at five different-aged revegetated sites (1956, 1964, 1973, 1982, and 1991) and at a ...reference site with native vegetation, which had never been damaged by sand burial and was enclosed for grazing. The proportions of silt and clay, depth of topsoil and biological soil crusts, and concentrations of soil organic C, K, total N and total P increased with years since revegetation. Most characteristics of topsoil (0–5 cm) characteristics had recovered to 60% of those measured at the reference site by 50 years after sand-binding vegetation had been established. Exceptions were electrical conductivity and contents of sand, silt, CaCO
3 and organic C, which recovered to 20–40% of the values at the reference site. The difference in annual recovery rates of soil properties between the two most recently revegetated sites (0–14 years) was greater than the difference between the two oldest revegetated sites (43–50 years). Best-fit asymptote models showed that the estimated times for the soil properties in the 50-year-old site to reach the same levels as in the reference site (i.e. an undisturbed, native steppified desert ecosystem) would be between 23 and 245 years, but for some properties even maximum recovery after >
50 years still fell significantly short of the level at the reference site. These results suggest that soil recovery is a slow process in an extremely arid desert environment, and therefore the conservation of soil habitat is a crucial issue for land managers.
Dear Editor Inflammation and oxidative stress can lower the functionality of apolipoprotein A-1 (ApoA1) and high-density lipoprotein (HDL) molecules, leading to defective reverse cholesterol ...transport and accelerating early atherosclerosis 1. ...a link between MPO levels and cholesterol efflux in human psoriasis has not been previously investigated. ...the aim of this study was to evaluate the relationship between MPO concentration and RCT in a cohort of chronically inflamed psoriasis patients. SEE PDF Similarly, between the two groups, we found no significant difference in HDL or LDL cholesterol, particle number and size, or triglyceride concentration (Table 1).
Lutein protects retinal neurons by its anti-oxidative and anti-apoptotic properties in ischemia/reperfusion (I/R) injury while its anti-inflammatory effects remain unknown. As Müller cells play a ...critical role in retinal inflammation, the effect of lutein on Müller cells was investigated in a murine model of I/R injury and a culture model of hypoxic damage.
Unilateral retinal I/R was induced by a blockade of internal carotid artery using the intraluminal method in mice. Ischemia was maintained for 2 hours followed by 22 hours of reperfusion, during which either lutein (0.2 mg/kg) or vehicle was administered. Flash electroretinogram (flash ERG) and glial fibrillary acidic protein (GFAP) activation were assessed. Lutein's effect on Müller cells was further evaluated in immortalized rat Müller cells (rMC-1) challenged with cobalt chloride-induced hypoxia. Levels of IL-1β, cyclooxygenase-2 (Cox-2), TNFα, and nuclear factor-NF-kappa-B (NF-κB) were examined by Western blot analysis.
Lutein treatment minimized deterioration of b-wave/a-wave ratio and oscillatory potentials as well as inhibited up-regulation of GFAP in retinal I/R injury. In cultured Müller cells, lutein treatment increased cell viability and reduced level of nuclear NF-κB, IL-1β, and Cox-2, but not TNFα after hypoxic injury.
Reduced gliosis in I/R retina was observed with lutein treatment, which may contribute to preserved retinal function. Less production of pro-inflammatory factors from Müller cells suggested an anti-inflammatory role of lutein in retinal ischemic/hypoxic injury. Together with our previous studies, our results suggest that lutein protected the retina from ischemic/hypoxic damage by its anti-oxidative, anti-apoptotic, and anti-inflammatory properties.
Aims
The short‐term effects of different organic manure nitrogen (N) input on soil ammonia‐oxidizing archaea (AOA) and bacterial (AOB) activity and community structure at maturity stages of early ...rice and late rice were investigated in the present paper, in a double‐cropping rice system in southern China.
Methods and Results
A field experiment was done by applying five different organic and inorganic N input treatments: (i) 100% N of chemical fertilizer (M0), (ii) 30% N of organic manure and 70% N of chemical fertilizer (M30), (iii) 50% N of organic manure and 50% N of chemical fertilizer (M50), (iv) 100% N of organic manure (M100) and (v) without N fertilizer input as control (CK). Microbial community changes were assessed using fatty acid methyl esters, and ammonia oxidizer (AO) changes were followed using quantitative PCR. The results showed that AOA were higher than that of AOB based upon amoA gene copy at maturity stages of early rice and late rice. Also, the abundance of AOB and AOA with M30, M50 and M100 treatments was significantly higher than that of CK treatment. Manure N input treatments had significant effect on AOB and AOA abundance, and a higher correlation between AOB and manure N input was observed. AOB correlated moderately with soil organic carbon content, and AOA correlated moderately with water‐filled pore space.
Conclusions
This study found that abundance of AOB and AOA was increased under the given organic N conditions, and the soil AOB and AOA community and diversity were changed by different short‐term organic manure N input treatments.
Significance and Impact of the Study
Soil microbial community and specific N‐utilizing microbial groups were affected by organic manure N input practices.
Construction safety is a serious problem in the construction industry worldwide, especially in large-scale construction projects. In order to improve the safety management performance, through the ...identification of the key factors that cause accidents, this research develops a conceptual framework of adopting virtual prototyping (VP) technology to aid in construction safety management. It consists of three components: modelling and simulation, the identification of unsafe factors, and safety training. A real-life case study is presented to demonstrate how to implement the VP-based safety management platform and evaluate its feasibility and validity. It is shown that the VP-based safety management platform can effectively aid in safety management and improve the safety performance of construction projects.
► The key factors causing construction accidents are identified. ► A conceptual framework of VP-based construction safety management is proposed. ► This framework is tested and evaluated by a real-life construction project. ► VP has the potential to aid in safety management and improve its performance.
Double perovskite oxides are one of the most promising bifunctional electrocatalysts for efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) due to their adjustable ...electronic structures via doping with different metal cations or engineering of defects. Herein, we report a systematic study on the tuning of the electronic structure of La2–x Sr x NiMnO6 with 0 ≤ x ≤ 1.0 to promote the bifunctional OER/ORR activity. The bifunctional index (ΔE) is substantially reduced with increasing of Sr contents and achieves an optimal value of 0.85 V for La1.4Sr0.6NiMnO6, exceeding that of widely studied LaNiO3. Our study on electronic structures reveals that the enhancement of the ORR and OER activities strongly correlates with the appearance of Ni3+ oxidation states and the upshift of the O 2p-band center promoted by Sr doping. Furthermore, an increase of hole states, derived from Ni3+ states, reduces the energy barrier for the electron transfer from 0.44 to 0.12 eV and hence improves the intrinsic OER activities. The tuning of the electronic structure that leads to higher OER and ORR activities in La2–x Sr x NiMnO6 can be extended to other materials for the design of active bifunctional electrocatalysts.
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