We report a first-principles density functional theory study of helium distribution in cementite Fe3C. The solution energy of interstitial He is similar to that in bcc Fe; by contrast, the ...substitutional He (replacing Fe) is remarkably (0.74eV) more stable than in the latter, due to the easiness of Fe vacancy formation in Fe3C. Therefore, He is predicted to be significantly more soluble in cementite than in Fe matrix. We find the binding potencies of both a substitutional–interstitial He pair (0.21eV) and a substitutional–substitutional He pair (0.22eV) are noticeably weaker in cementite than in bcc Fe, indicating a less powerful self-trapping. As a consequence, small size cementite in ferritic steels might serve as scattered trapping centers for He, mitigate helium bubble growth, and make the steel more swelling resistant while under neutron irradiation, just as dispersed oxide particles do.
Background and Purpose
Orexins have been demonstrated to play important roles in many physiological processes. However, it is not known how orexin A affects the activity of the hypoglossal motoneuron ...(HMN) and genioglossus (GG) muscle.
Experimental Approach
GG muscle electromyograms (GG‐EMG) were recorded in anaesthetized adult rats after orexin A or orexin receptor antagonists were applied to the hypoglossal nucleus, and in adult rats in which orexin neurons were lesioned with the neurotoxin orexin‐saporin (orexin‐SAP). HMN membrane potential and firing were recorded from neonatal rat brain slices using whole‐cell patch clamp after an infusion of orexin A or orexin receptor antagonists.
Key Results
Unilateral micro‐injection of orexin A (50, 100 or 200 μM) into the hypoglossal nucleus significantly enhanced ipsilateral GG activity in adult rats. Orexin A (4, 20, 100 or 500 nM) depolarized the resting membrane potential and increased the firing rate of HMNs in a dose‐dependent manner in the medullary slices of neonatal rats. Both SB 334867, a specific OX1 receptor antagonist and TCS OX2 29, a specific OX2 receptor antagonist not only blocked the depolarized membrane potential and the increased firing rate of HMNs by orexin A in the neonatal model but also attenuated GG‐EMG in the adult model. A significant decrease in GG‐EMG was observed in adult orexin neuron‐lesioned rats compared with sham animals.
Conclusion and Implications
Orexin A activates OX1 and OX2 receptors within the hypoglossal motor pool and promotes GG activity, indicating that orexin A is involved in controlling respiratory motor activity.
Gold might slow down the growth of helium bubble in iron Hao, W.; Geng, W.T.
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
06/2011, Letnik:
269, Številka:
12
Journal Article
Recenzirano
Odprti dostop
► Au is predicted to strongly bound to He in bcc Fe. ► A segregated Au layer may form at the He bubble surface. ► The Au layer slows down the bubble growth.
We predict by first-principles ...calculations that Au is strongly bound to He in bcc Fe. Therefore, a segregated Au layer may form at the He bubble surface. The electron density in between Au–Au is found to be remarkably higher than in between Fe–Fe and Au–Fe atoms. As a result, the Au layer could serve as an effective barrier to approaching He atoms and hence slow down the bubble growth.
To explore the changes of cerebral blood perfusion in patients with unilateral sudden sensorineural hearing loss (SSNHL) by using the three-dimensional pseudo-continuous arterial spin labeling (3D ...pCASL) technique.
The clinical characteristics and ASL data of the 32 patients with unilateral SSNHL were retrospectively collected from November 2020 to June 2021 in Beijing Fuxing Hospital of Capital Medical University, among them, there were 7 males and 25 females, aged from 17 to 73 (44.9±14.4) years. According to the location of SSNHL, they were divided into the left SSNHL (L-SSNHL) group (18 cases) and the right SSNHL (R-SSNHL) group (14 cases). A total of 34 healthy volunteers, which including 14 males and 20 females, aged from 24 to 68 (46.2±14.4) years were enrolled from the local community. The parameter of cerebral blood flow (CBF) of each brain area was obtained using the CereFlow software. The Brainnetome Atlas software package based on MATLAB was used for visualization. The independent-samples
test was
In this paper, the degradation behavior of the electrical characteristics was investigated, and trap analysis based on low-frequency noise (LFN) was carried out for the commercial 1.2-kV/30-A silicon ...carbide (SiC) power MOSFETs under repetitive short-circuit (SC) stress. The experiment results show that the on-state resistance (R dson ) and threshold voltage (V th ) increase significantly. Meanwhile, the drain-source current (I ds ) decreases obviously with the increase of the SC cycles. Furthermore, the gatesource leakage current (I gss ) of the SiC power MOSFETs increase greatly and the blocking characteristics deteriorated after 1000 SC cycles. The positive shift was observed on the gate-capacitance versus gatevoltage (C g -V g ) curve, which shows that the damage region could be in channel along the SiC/SiO 2 interface after repetitive SC stress. In order to obtain the trap information, trap characterization was performed by using LFN method, and the LFN results show that the trap density increases with the SC cycles. The physical mechanism could be attributed to electrically active traps generated at SiC/SiO 2 interface and oxide layer due to the peak ionization rate, the perpendicular electrical field and high temperature during SC stress. The study may be useful to provide reference for converters design and fault protection of SiC power MOSFETs.
To further improve the comprehensive performance of existing impact-resistant steel, rare-earth-modified steel samples were experimentally prepared and their performance was analyzed. Different ...amounts of mixed rare earths were added into the 30MnCrNiMo impact-resistant steel, followed by vacuum smelting, forging, and rolling to prepare the steel plate. The effects of rare earths on the phase transformation critical points, high-temperature deformation behavior, microstructure, and mechanical properties were studied. The results show that rare earths can play a purifying role in the test steel. The Ac1-Ac3 phase transition temperatures were increased, and those of the Bs-Bf phase transition were decreased significantly. When compressed at 1000 °C, the deformation resistance of the test steel with rare earth became higher. Thus, the added rare earths improve the microstructural morphology and inclusions in the steel, as well as the comprehensive mechanical properties.
Both helium and hydrogen are known to degrade the mechanical performance of reactor materials, but their binary effect has not been well understood. Using
ab
initio density functional theory ...calculations, we have investigated the He–H interactions both in the bulk and at the grain boundary in bcc Fe. We find an attraction of 0.56
eV between one substitutional He and one interstitial H in the bulk and a repulsion of 0.20
eV at the Σ3 (1
1
1)
1
1
¯
0
grain boundary. The attraction of He and H inside a grain means a reduction of combined embrittling effect in intra-granular fracture and the repulsion at the grain boundary means an enhancement of combined embrittling effect in inter-granular fracture. The interaction of He and H are interpreted with electronic structure analyses.
In September 2015, the 193 Member States of the United Nations (UN) unanimously adopted the 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals (SDGs), aiming to ...transform the world over the next 15 years (ESDN, 2016). To meet the ambitions and demands of the 2030 Agenda, it is necessary for the global indicator framework to adequately and systematically address the issue of alternative data sources and methodologies, including geospatial information and Earth observations in the context of geographic location (UN-GGIM, 2016). For this purpose, the Inter-Agency and Expert Group on Sustainable Development Goals Indicator (IAEG-SDGs) created the Working Group on Geospatial Information (IAEG-SDGs: WGGI) to give full play to the role of geospatial data in SDGs measurement and monitoring. The Working Group reviewed global indicators through a ‘geographic location’ lens to pick out those which geospatial information can significantly support the production, and analyzed the methodological and measurements issues. This paper has discussed the progress in monitoring SDGs ever since the establishment of IAEG-SDGs: WGGI, as well as the existing problems, appropriate solutions and plans for the next stage of work.
The crystallographic alignment, microstructure and magnetic properties were studied for La0.6Ca0.6Sr0.1Fe12.4Co0.4O19 ferrite permanent magnets prepared with standard ceramic method. The effect of ...cold isostatic pressing (CIP) and sintering temperature on the structural and magnetic properties of the magnets were investigated. The CIP significantly improves the density of the green compact and final magnets, but undermines the crystallographic alignment of the magnets simultaneously. As a result, the remanence of the magnet achieves optimal value under the compromise between the increased density and the degraded alignment. Moreover, the coercivity of the magnet increases linearly with the increment of the CIP pressure due the fact that CIP processed samples bear more uniform and finer grains in favor of high coercivity. Under optimal CIP pressure and sintering temperature, the magnet obtains best magnetic properties of Br of 0.439 T, Hcj of 396 kA m−1, Hcb of 311 kA m−1, and (BH)maxof 35.8 kJ m−3.
Low-temperature drying is becoming recognized as an optimal type of hot drying technology for agricultural and sideline products. This study presents an experimental study on drying roses with a heat ...pump dehumidifier. The rose drying process took 40 hours across three drying stages, where the hot air temperatures were 45°C, 50°C and 55°C respectively. The dried roses were brightly colored and good quality, also, rose water was obtained during the drying process when the waste heat was recovered. The major components of the rose water were rose ether, nerol, citronellol, acetic acid, phenylethyl alcohol, methyleugenol, and so on, which are typical compounds of rose essential oil. The results show that a heat pump is one of best choices for drying rose flowers, and that rose water can also be effectively recovered during the drying process.
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