1,572 research outputs found
Device modelling of a field emission displays
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (p. 71-72).by Pei-Ning Wang.M.Eng
Quantifying the controls on evapotranspiration partitioning in the highest alpine meadow ecosystem
Quantifying the transpiration fraction of evapotranspiration (T/ET) is crucial for understanding plant functionality in ecosystem water cycles, land‐atmosphere interactions, and the global water budget. However, the controls and mechanisms underlying the temporal change of T/ET remain poorly understood in arid and semiarid areas, especially for remote regions with sparse observations such as the Tibetan Plateau (TP). In this study, we used combined high‐frequency laser spectroscopy and chamber methods to constrain estimates of T/ET for an alpine meadow ecosystem in the central TP. The three isotopic end members in ET (δET), soil evaporation (δE), and plant transpiration (δT) were directly determined by three newly customized chambers. Results showed that the seasonal variations of δET, δE, and δT were strongly affected by the precipitation isotope (R2 = 0.53). The δ18O‐based T/ET agreed with that of δ2H. Isotope‐based T/ET ranged from 0.15 to 0.73 during the periods of observation, with an average of 0.43. This mean result was supported by T/ET derived from a two‐source model and eddy covariance observations. Our overarching finding is that at the seasonal timescale, surface soil water content (θ) dominated the change of T/ET, with leaf area index playing only a secondary role. Our study confirms the critical impact of soil water on the temporal change of T/ET in water‐limited regions such as the TP. This knowledge sheds light on diverse land‐surface processes, global hydrological cycles, and their modeling
Surface grinding of carbon fiber-reinforced plastic composites using rotary ultrasonic machining: Effects of tool variables
Citation: Wang, H., Ning, F. D., Hu, Y. B., Fernando, P., Pei, Z. J., & Cong, W. L. (2016). Surface grinding of carbon fiber-reinforced plastic composites using rotary ultrasonic machining: Effects of tool variables. Advances in Mechanical Engineering, 8(9), 14. doi:10.1177/1687814016670284Carbon fiber-reinforced plastic composites have many superior properties, including low density, high strength-to-weight ratio, and good durability, which make them attractive in many industries. However, due to anisotropic properties, high stiffness, and high abrasiveness of carbon fibers in carbon fiber-reinforced plastic, high cutting force, high tool wear, and high surface roughness are always caused in conventional machining processes. This article reports an investigation using rotary ultrasonic machining in surface grinding of carbon fiber-reinforced plastic composites in order to develop an effective and high-quality surface grinding process. In rotary ultrasonic machining surface grinding of carbon fiber-reinforced plastic composites, tool selection is of great importance since tool variables will significantly affect output variables. In this work, the effects of tool variables, including abrasive size, abrasive concentration, number of slots, and tool end geometry, on machining performances, including the cutting force, torque, and surface roughness, are experimentally studied. The results show that lower cutting forces and torque are generated by the tool with higher abrasive size, lower abrasive concentration, and two slots. Lower surface roughness is generated by the tool with smaller abrasive size, smaller abrasive concentration, two slots, and convex end geometry. This investigation will provide guides for tool selections during rotary ultrasonic machining surface grinding of carbon fiber-reinforced plastic composites
Oxidation kinetics and non-Marcusian charge transfer in dimensionally confined semiconductors
Electrochemical reactions represent essential processes in fundamental
chemistry that foster a wide range of applications. Although most
electrochemical reactions in bulk substances can be well described by the
classical Marcus-Gerischer charge transfer theory, the realistic reaction
character and mechanism in dimensionally confined systems remain unknown. Here,
we report the multiparametric survey on the kinetics of lateral photooxidation
in structurally identical WS2 and MoS2 monolayers, where electrochemical
oxidation occurs at the atomically thin monolayer edges. The oxidation rate is
correlated quantitatively with various crystallographic and environmental
parameters, including the density of reactive sites, humidity, temperature, and
illumination fluence. In particular, we observe distinctive reaction barriers
of 1.4 and 0.9 eV for the two structurally identical semiconductors and uncover
an unusual non-Marcusian charge transfer mechanism in these dimensionally
confined monolayers due to the limit in reactant supplies. A scenario of band
bending is proposed to explain the discrepancy in reaction barriers. These
results add important knowledge into the fundamental electrochemical reaction
theory in low-dimensional systems.Comment: 20 pages, 4 figure
Influence of Reducing Agents on Biosafety and Biocompatibility of Gold Nanoparticles
Extensive biomedical applications of nanoparticles are mainly determined by their safety and compatibility in biological systems. The aim of this study was to compare the biosafety and biocompatibility of gold nanoparticles (GNPs) prepared with HEPES buffer, which is popular for cell culture, and sodium citrate, a frequent reducing agent. From experimental results on the body weight and organ coefficients of acute oral toxicity tests, it could be observed that HEPES-prepared GNPs are biologically safer than citric-prepared GNPs at the same dose of 500 μg/kg. The in vitro cell viability was higher for HEPES-prepared GNPs than citric-prepared GNPs at 5.0- and 10.0-ug/mL concentrations. More reactive oxygen species (ROS) were generated in the cell suspension when supplemented with citric-prepared GNPs than HEPES-prepared GNPs when their concentrations were higher than 20 μg/mL. The results stated that HEPES-prepared GNPs had better biosafety and biocompatibility than citric-prepared GNPs. This study not only revealed the influence of reducing agent on biosafety and biocompatibility of nanomaterials but also provided accumulative evidence for nanomaterials in biomedical applications. [Figure: see text
A missense mutation in PKD1 attenuates the severity of renal disease
Mutations of PKD1 and PKD2 account for most cases of autosomal dominant polycystic kidney disease (ADPKD). Compared with PKD2, patients with PKD1 typically have more severe renal disease. Here, we report a follow-up study of a unique multigeneration family with bilineal ADPKD (NFL10) in which a PKD1 disease haplotype and a PKD2 (L736X) mutation co-segregated with 18 and 14 affected individuals, respectively. In our updated genotype–phenotype analysis of the family, we found that PKD1-affected individuals had uniformly mild renal disease similar to the PKD2-affected individuals. By sequencing all the exons and splice junctions of PKD1, we identified two missense mutations (Y528C and R1942H) from a PKD1-affected individual. Although both variants were predicted to be damaging to the mutant protein, only Y528C co-segregated with all of the PKD1-affected individuals in NFL10. Studies in MDCK cells stably expressing wild-type and mutant forms of PKD found that cell lines expressing the Y528C variant formed cysts in culture and displayed increased rates of growth and apoptosis. Thus, Y528C functions as a hypomorphic PKD1 allele. These findings have important implications for pathogenic mechanisms and molecular diagnostics of ADPKD
PASSion: a pattern growth algorithm-based pipeline for splice junction detection in paired-end RNA-Seq data
Motivation: RNA-seq is a powerful technology for the study of transcriptome profiles that uses deep-sequencing technologies. Moreover, it may be used for cellular phenotyping and help establishing the etiology of diseases characterized by abnormal splicing patterns. In RNA-Seq, the exact nature of splicing events is buried in the reads that span exon–exon boundaries. The accurate and efficient mapping of these reads to the reference genome is a major challenge
Effect of Xinyue capsules on patients with coronary heart disease after percutaneous coronary intervention: study protocol for a randomized controlled trial
Case report form 2014.3.4R2. (PDF 1119 kb
Fetal Magnetic Resonance Imaging Demonstration Of Central Nervous System Abnormalities and Polydactyly Associated With Joubert Syndrome
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