Novel high-density aluminum (Al)-tungsten (W) fiber composites in the tubular shape with highly ordered tungsten fibers in axial and hoop directions were processed in the solid state using the ...combination of cold isostatic pressing and hot isostatic pressing. Half of the specimens were additionally heat treated after hot isostatic pressing to regain the properties of aluminum 6061-T6. The strength of both types of samples was investigated under quasistatic compression. Samples after additional heat treatment had the higher microhardness of matrix and compressive strength. No significant reaction between tungsten fibers and aluminum matrix was detected. The micromechanism of samples failure under compression was revealed by removing the aluminum matrix after tests with acid-etching demonstrating that tungsten fibers oriented in the axial direction were deformed by microbuckling and kinking. The sample bulging due to plastic flow of aluminum matrix resulted in the cooperative fracture of tungsten fibers in the hoop direction.
•High-density Al-W fiber composite tubes with periodically ordered W fibers were processed by using Cold and Hot Isostatic Pressing, and subsequent heat treatment (HT).•The tubes were dynamically ...tested and samples after additional HT had higher microhardness of Al matrix and increased compressive strength.•Composites demonstrated strain rate sensitivity mostly due to W fibers.•The samples failure is due to the buckling and kinking of W fibers oriented in the axial direction, sample bulging and the subsequent fracture of W fibers in the hoop direction.
The split Hopkinson pressure bar was used to investigate the dynamic behavior of high density aluminum alloy (Al 6061-T6) – tungsten (W) fibers composite tubes with periodic arrangements of W fibers in axial and hoop directions processed by using the combination of Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing (HIPing). Additional heat treatment of some samples allowed them to regain the original strength of Al 6061-T6, which was annealed during HIPing. The high-strain-rate deformation resulted in the strength increase for both types of samples (with and without the heat treatment) compared to quasi-static deformation. Samples after additional heat treatment exhibited higher dynamic strength. We consider that the strain rate sensitivity of the composite samples is caused by W fibers, which are responsible for the high strength of the samples and mechanism of their fracture.
After dynamic tests, the Al matrix was chemically removed from the heavily deformed samples to reveal the mode of deformation of the W fibers: microbuckling and kinking in the axial direction. These mechanisms initiated the fracture of the composite samples followed by sample bulging due to plastic flow of the Al matrix and the subsequent fracture of W fibers in the hoop direction.
The targeted delivery of therapeutic agents is a promising approach to enhance the efficacy and reduce the toxicity of cancer treatments. Understanding the intracellular endocytic mechanisms of a ...cell penetrating peptide (CPP) in an acidic environment is important for targeted delivery of macromolecules to tumours. In this study, we constructed a pH-sensitive CPP-based delivery system for the intracellular delivery of macromolecules. A pH-sensitive CPP, HBHAc, was fused with a model protein, enhanced green fluorescent protein (EGFP), through recombinant DNA technology. We found that is essential that negatively charged proteoglycans on the cell surface interact with HBHAc-EGFP prior to the cellular uptake of HBHAc-EGFP. The uptake was significantly restricted at 4 °C under pH conditions of both 6.5 and 7.5. The increased positive charge of HBHAc-EGFP under the acidic condition leads to a pH-dependent cellular uptake, and we observed that the internalisation of HBHAc-EGFP was significantly higher at pH 6.5 than at pH 7.5 (p < .05). Thus, with pH-sensitive activity, HBHAc is expected to improve tumour-targeted intracellular protein delivery. Moreover, our findings provide a new insight that the endocytic pathway may change under different pH conditions and suggest that this unique phenomenon benefits pH-sensitive drug delivery for tumour therapy.
•Fluorescence experiments are conducted on a tetracene/LiF/Si sample.•The fluorescence intensity of tetracene increases as LiF thickness increases.•Prompt fluorescence lifetimes decrease as the ...tetracene thickness increases.•No evidence is found for triplet energy transfer from tetracene to the Si.
Tetracene, a molecule that undergoes singlet fission, is deposited on Si with variable thickness LiF spacer layers. In agreement with earlier work (Hayashi et al., 1983 10), the fluorescence intensity of the tetracene greatly increases as the LiF thickness approaches 100nm. This increase is partly due to a 30% increase in the prompt fluorescence decay time but mostly results from weaker coupling of the luminescence into the Si substrate. A decrease in the prompt fluorescence lifetime is observed as the tetracene thickness is increased on bare Si. We find no evidence for triplet energy transfer to the Si.
This letter investigates the influence of ammonia on amorphous carbon resistance random access memory by sputtering the carbon target with argon and ammonia mixed gas. The device fabricated with ...ammonia (C (NH 3 )-RRAM) showed remarkable improvement in memory window and high resistance state as compared to the device deposited without ammonia. Material analysis confirmed the absorption signal of amine. Current fitting indicated the conduction mechanism changes from hopping conduction to Schottky conduction with the addition of ammonia. Finally, we propose a model to explain the influence of ammonia on the resistive switching behaviors of the amorphous carbon RRAM.
In this letter, we propose a resistive switching memory with outstanding comprehensive performance by inserting buffer layers of silicon dioxide doped with boron nitride (BN: SiO 2 into HfO ...resistance random access memory (RRAM). X-ray photoelectron spectroscopy (XPS) spectra confirms that hexagonal boron nitride (h-BN) exists in the BN:SiO 2 layer. The Pt/BN:SiO 2 /HfO/BN:SiO 2 /TiN structure was observed to have superior switching endurance >10 12 cycles) and higher stability. This can be attributed to the oxygen ions generated during the forming process being localized by h-BN flakes which are formed during the sputter process. A physical model is proposed to explain the resistive switching behavior of HfO RRAM with the inserted BN-based layers.
Background
Epicardial adipose tissue is associated with coronary artery disease (CAD). Circulating endothelial progenitor cell (EPC) level represents a marker of endothelial dysfunction and vascular ...health. However, the relationship between epicardial fat and circulating EPC remains unknown. This study aimed to investigate association between echocardiographic epicardial fat thickness (EFT) and circulating EPC level.
Hypothesis
Epicardial fat causes inflammation and contributes to progression of CAD.
Methods
We enrolled 213 consecutive patients with stable angina, and EFT was determined by echocardiography. Quantification of EPC markers (defined as CD34
+, CD34
+
KDR
+, CD34
+
KDR
+
CD133
+ cells) in peripheral blood samples was used to measure circulating EPCs. All patients were divided into 3 tertiles according to EFT levels: group 1, low tertile of EFT; group 2, middle tertile of EFT; and group 3, high tertile of EFT.
Results
Among the 3 groups, CAD disease severity determined by SXscore was negatively correlated with EFT, but the difference did not reach statistical significance (P = 0.066). Additionally, patients in the high and middle tertiles of EFT had higher circulating EPC levels than did those in the low tertile of EFT (P = 0.001 and P < 0.001, respectively). In multivariate analysis, EPC level was significantly associated with echocardiographic EFT (standardized β = −0.233, P = 0.001), independent of multiple covariates.
Conclusions
Epicardial adipose tissue is associated with circulating EPC levels. There was a trend between epicardial fat and severity of CAD, though analysis did not reach statistical significance, and this may be attributed to the interaction between several risk factors of CAD.
•The role of the microstructure of AISI 4340 steel with different values of microhardness on shear band nucleation and post-critical behavior was experimentally explored with the help of the ...explosively-driven Thick-Walled Cylinder technique.•As-received AISI 4340 steel was resilient to shear localization and propagation.•The hardened specimens of AISI 4340 steel at the similar final global strains exhibited dramatically different behavior.•High global strains in both steels were accommodated by growth of the initially generated shear bands.•LS-DYNA based numerical simulations reproduced the main features observed in the experiments and were able to address the dramatic difference in behavior of as-received and hardened AISI 4340 steel.•The initial number of defects introduced in calculations is crucial to generate the observed pattern of shear bands and post critical behavior.
We explore the role of the microstructure of AISI 4340 steel with different values of microhardness (as-received and hardened) on shear band nucleation and post-critical behavior with a well-developed pattern of shear bands. Critical and post-critical behavior was investigated with the help of the explosively-driven Thick-Walled Cylinder technique, which allowed comparative study of the material deformation at similar strain rates and final strains. It was observed that the collapsed as-received AISI 4340 samples were resilient to shear localization and propagation and mainly preserved its cylindrical geometry at the investigated small and larger global strains. The hardened specimens at the similar final global strains exhibited a dramatically different behavior. At small strains, some well-developed shear bands were observed. Larger global strains were accommodated mostly by growth of the initially generated shear bands, resulting in the complete loss of cylindrical symmetry. Numerical simulations reproduced the main features observed in the experiments and the dramatic difference in behavior of as-received and hardened AISI 4340 steel. It is shown that the initial number of defects introduced in calculations as well as the material constants used for the material model have a direct effect on the pattern of shear bands.
Background Systemic lupus erythematosus (SLE) has been reported to be associated with an increased risk of cardiovascular disease. However, most studies have been criticized for either a small sample ...size or the lack of a prospective control. Our study investigated the relationship of SLE and the subsequent development of ischemic stroke using a nationwide, population-based database in an Asian population. Methods From 2000 to 2007, we identified a study cohort consisting of a total of 11,637 newly diagnosed SLE patients using the National Health Insurance Research Database in Taiwan. A control cohort of 58,185 subjects without SLE, matched for age, gender, and comorbidities were selected for comparison to observe the occurrence of ischemic stroke in these two groups. Results During a follow-up period of up to 7 years, ischemic stroke developed in 258 (2.22%) of the patients with SLE and in 873 (1.5%) of patients in the comparison cohort. Kaplan-Meier analysis also revealed a tendency of SLE patients toward ischemic stroke development (log rank test, p = 0.001). After Cox model adjustment for patients' demographic characteristics and selected comorbidities, patients with SLE were found to have a 1.67-fold (95% CI, 1.45 to 1.91) higher risk of developing ischemic stroke. Conclusion Patients with SLE have an increased risk of stroke.
In this paper, we implement a post-oxidation method to modify surface characteristics of indium tin oxide (ITO) films by using an O2 inductively coupled plasma (ICP) treatment. Based on field ...emission-scanning electron microscope (FE-SEM) and atomic force microscope (AFM) analysis, we found that the surface morphologies of the ITO films become slightly flatter after the O2 plasma treatment. The optical characteristics and X-ray diffraction (XRD) experiments of either pure ITO or O2 plasma treated ITO films were also verified. Even though the XRD results showed no difference from bulk crystallizations, the oxygen concentrations increased at the film surface after O2 plasma treatment, according to the XPS inspection results. Moreover, this study investigated the effects of two different plasma treatment times on oxygen concentration in the ITO films. The surface sheet resistance of the plasma treated ITO films became nearly non-conductive when measured with a 4-point probe. Finally, we applied the O2 plasma treated ITO films as the insulator in resistive random access memory (RRAM) to examine their potential for use in resistive switching storage applications. Stable resistance switching characteristics were obtained by applying the O2 plasma treatment to the ITO-based RRAM. We also confirmed the relationship between plasma treatment time and RRAM performance. These material analyses and electrical measurements suggest possible advantages in using this plasma treatment technique in device fabrication processes for RRAM applications.
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