We have fabricated the Cu (50nm)/Nb–Ni (5nm)/Si heterostructures, annealed at various temperatures up to 800°C in a high vacuum system, to investigate the barrier performance of the ultrathin ...amorphous Nb–Ni film between Cu and Si. No impurity peaks are observed from the X-ray diffraction patterns of the Cu/Nb–Ni/Si heterostructures annealed up to 800°C. The island-like surface is observed for the 800°C annealed sample, indicating the failure of the Nb–Ni barrier layer, which is attributed to agglomeration of Cu film resulting from the dewetting of Cu with the underlying Nb–Ni layer during high temperature annealing. The activation energy for Cu dewetting with Nb–Ni layer is estimated to be 0.86eV. Our result demonstrates that ultra-thin amorphous Nb–Ni film can be an ideal diffusion barrier layer for Cu interconnection.
•5-nm-thick Nb–Ni is used first as a diffusion barrier layer between Cu and Si.•The ultrathin Nb–Ni film has a very good barrier performance up to 750°C.•Dewetting of Cu originates from the void nucleation at the Cu/Nb–Ni interface.•The cheap and simply ultra-thin Nb–Ni can be an ideal diffusion barrier layer.
ABSTRACT
We studied the 2018 outburst of the black hole transient H 1743 − 322 with a series of Insight-HXMT, NICER, and NuSTAR observations, covering the 1–120 keV band. With our broad-band X-ray ...spectral modelling, we confirm that the source remained in the low/hard state throughout the month-long outburst, although it became marginally softer at peak flux. We detected Type-C quasi-periodic oscillations (QPOs) and followed the evolution of their properties. The QPO frequency increased from ∼0.1 to ∼0.4 Hz during the rising phase of the outburst and decreased again in the decline. Continuum X-ray flux, power-law photon index, QPO frequency, and QPO root-mean-square amplitude were positively correlated. The QPO amplitude was slightly higher in the soft X-ray band (typical values of 12–16 per cent, compared with 8–10 per cent in the hard band). Our spectral-timing results shed light on the initial rising phase in the low/hard state, which has rarely been monitored with such high cadence, time resolution, and broad-band coverage. Combining spectral and timing properties, we find that ‘failed’ (hard state only) and ‘successful’ outbursts follow the same initial evolutionary track, although the former class of outburst never reaches the threshold for a transition to softer (thermally dominated) accretion regimes.
Zirconium alloys show attractive properties for astronautic applications where the most important factors are anti-irradiation, corrosion resistance, anti-oxidant, very good strength-to-weight ratio. ...The effects of Al content (2.2-6.9wt%) on structure and mechanical properties of the hot-rolled ZrTiAlV alloy samples were investigated in this study. Each sample of the hot-rolled ZrTiAlV alloys with Al contents from 2.2wt% to 5.6wt% is composed of the alpha phase and beta phase, meanwhile, the relative content of the alpha phase increased with the Al content. However, the (ZrTi)3Al intermetallic compound was observed as the Al content increased to 6.9wt%. Changes of phase compositions and structure with Al content distinctly affected mechanical properties of ZrTiAlV alloys. Yield strength of the alloy with 2.2wt% Al is below 200MPa. As Al content increased to 5.6wt%, the yield strength, tensile strength and elongation of the examined alloy are 1088MPa, 1256MPa and 8%, respectively. As Al content further increased to 6.9wt%, a rapid decrease in ductility was observed as soon as the (ZrTi)3Al intermetallic compound precipitated. Results show that the ZrTiAlV alloys with Al contents between 3.3wt% and 5.6wt% have excellent mechanical properties.
The microstructural features of M
23
C
6
carbide in a long-term aged heat- and corrosion-resistant Ni-based superalloy have been investigated in detail using various kinds of transmission electron ...microscope (TEM) techniques. It is found that TEM contrast, which is related to structural and chemical inhomogeneities inside the grains, always exists in the interior of grains in the alloy. The structure of these inhomogeneous regions has been determined to be the same as that of the γ′ and t-M
23
C
6
phases, where t-M
23
C
6
indicates a transitional and metastable phase. Although possessing the same structure as the M
23
C
6
phase, the chemical composition of the t-M
23
C
6
is different from that of the M
23
C
6
phase. Compared with M
23
C
6
, t-M
23
C
6
is richer in Ni, Co, Al and Ti but poorer in W, Mo and Cr. This phenomenon of structural and chemical inhomogeneity demonstrates that pristine M
23
C
6
carbide (p-M
23
C
6
) precipitated in standard heat-treated samples is unstable. Therefore, upon long-term ageing treatment, Ni, Co, Al and Ti may locally enrich inside the p-M
23
C
6
phase, finally forming the γ′ phase, which can be described by the decomposition reaction p-M
23
C
6
→ M
23
C
6
+ γ′.
The lower developmental threshold (LDT) and the number of developmental degree days (DDs) are fundamental parameters used to build phenology models that can be used to predict the timing of ...biological events during insect development. The Chinese citrus fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae) is one of the most destructive citrus pest in China and Bhutan. This species overwinters as diapausing pupae in the soil before emerging as adults in the spring. In this study, B. minax collected from three representative geographical populations in China (Guizhou, Hubei, and Shaanxi) was used to conduct LDT experiments under laboratory conditions. Emergence data collected from pupae exposed to 10 constant temperatures was used to estimate the LDT and DDs required to complete pupal development for the three populations. The results show that LDT and DDs values for the Hubei and Shaanxi population are 11.9°C, 447.3 DDs and 11.5°C, 511.3 DDs, respectively. However, the geographic variation in pupal developmental rates was not statistically significant between the two populations. In addition, the Guizhou population was identified as a mixture of B. minax and B. tsuneonis (Miyake). The LDT and DDs values for the Hubei and Shaanxi populations obtained in this study can be used to predict adult emergence of naturally occurring field populations of B. minax within the majority of the citrus-growing production areas of China. These data can also be used in models to predict the risk of establishment of this species in the United States or other citrus-growing regions.
Antiviral defense of plants is usually enhanced by an elevated temperature under natural conditions. In order to better understand this phenomenon, we carried out temperature shift experiments with ...Nicotiana glutinosa plants that were infected with Potato virus X (PVX) or the necrotic strain of Potato virus Y (PVY(N)). The virus titer of the plants was found to be much lower when they were maintained at 30°C compared with 22°C, particularly in the upper leaves. PVX resistance at 30°C persisted for a short period even when temperature was shifted back to 22°C. In contrast, N. benthamiana lost the virus resistance immediately after the temperature dropped to 22°C. Expression analysis of two RNA-dependent RNA polymerases in N. glutinosa (NgRDR) showed that a 12-day treatment at 30°C increased the expression of NgRDR1, while NgRDR6 was not affected. In addition, the NgRDR6 mRNA level correlated with the PVX titer but was unaffected by PVY(N) infection. These observations indicate that PVX and PVY(N), although they are both RNA viruses, might trigger different defense responses at elevated temperatures. Our study provides valuable data for a better understanding of the temperature-regulated host virus interaction.
Purpose: The association between serum osteocalcin (OCN) levels and metabolic dysfunction-associated fatty liver disease (MAFLD) is still controversial. Moreover, few studies have explored their ...relationship in type 2 diabetes mellitus (T2DM) patients so far. The present study aimed to investigate the association of serum OCN levels with MAFLD in Chinese T2DM patients. Methods: This cross-sectional, real-world study included 1889 Chinese T2DM inpatients. MAFLD was diagnosed by abdominal ultrasonography. Participants were divided into four groups according to serum OCN quartiles, among which the clinical characteristics were compared. The association of serum OCN levels with the presence of MAFLD was also analyzed in subjects. Results: After controlling for sex, age, and diabetes duration, the prevalence of MAFLD significantly decreased across the serum OCN quartiles (55.3%, 52.0%, 48.6%, and 42.1% for the first, second, third, and fourth quartiles, respectively, P < 0.001 for trend). A fully adjusted multiple logistic regression analysis showed that serum OCN levels were independently and negatively associated with the presence of MAFLD in T2DM patients (odds ratio, 0.832; 95% confidence interval, 0.719-0.962; P = 0.013). Furthermore, there were significant decreases in HOMA-IR (P = 0.001 for trend) and C-reactive protein (P < 0.001 for trend) levels across the serum OCN quartiles after controlling for sex, age, and diabetes duration. Conclusion: Serum OCN levels were independently and negatively associated with the presence of MAFLD in Chinese T2DM patients, partially due to the improvement of insulin resistance and inflammation mediated by OCN. Serum OCN may be used as a biomarker to assess the risk of MAFLD in T2DM patients. Keywords: diabetes mellitus, type 2, metabolic dysfunction-associated fatty liver disease, osteocalcin, insulin resistance, inflammation
In order to improve the ZrC-SiC ceramic and TC4 brazed joint property, graded double-layered SiC particles (SiCp)-reinforced TC4-based composite structure (named as GLS for convenience) was designed ...to relieve the residual stress in the joint. The GLS was successfully fabricated on TC4 substrate by double-layered laser deposition technology before the brazing process. The investigation of the GLS shows that the volume fraction of SiCp in the two composite layers was graded (20 and 39 vol pct, respectively). Ti
5
Si
3
and TiC phases formed in the GLS due to the reaction of SiCp and TC4. The laser power-II (the laser power for the second deposition layer) affected the microstructure of the GLS significantly. Increasing the laser power-II would promote the reaction between the SiCp and TC4. But the high laser power-II made the layer I remelt completely and the two layers became homogeneous rather than graded structure. In the ZrC-SiC and TC4 brazed joint, the CTE (coefficient of thermal expansion) was graded from the TC4 to the ZrC-SiC due to the GLS, and the strength of the joint with the GLS (91 MPa) was higher than that without the GLS (43 MPa).
In order to monitor the insulation condition of XLPE cables which have been one of the most popular equipment used in power transition, a method is proposed in this paper to identify the insulation ...defects accurately by analysing the Weibull distribution of partial discharge (PD) signals. Experiments were applied on a 10kV 30m XLPE cable and three typical types of insulation defect models were designed and tested. The discharge pulse signals of each defect model were collected and their Weibull parameters were analysed and estimated with the ordinary least square estimation method. Several common pattern recognition methods such as support vector machine (SVM), artificial neural network (ANN) as well as classification and regression tree (CART) were used to test the accuracy of the extracted Weibull parameters. The results verified that it is effective to use the parameters of Weibull distribution for defect identification of XLPE cables and the features are suitable for common pattern recognition models.
The longitudinal dynamics of RF-bunched and electron cooled ion beams have been studied at the experimental cooler storage ring (CSRe), at IMP Lanzhou. By RF-bunching the ion beam at the 50th and ...100th harmonic of the revolution frequency, the longitudinal momentum spread and the bunch length of the 22Ne10+ ion beam with an energy of 70MeV/u were measured by the new resonant Schottky pick-up and the capacitive pick-up, respectively. A minimum momentum spread of Δp/p=1.6×10−5 has been reached with less than 107 ions stored in the ring. By using the harmonic potential extracted from the Taylor expansion and the real sinusoidal potential of the bucket, the trend of momentum spread and synchrotron frequency as well as the bunch length as a function of beam current can be interpreted very well. According to this experiment, the RF-buncher is suitable for upcoming experiments on laser cooling of relativistic heavy ion beams at the CSRe.
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