New Developments in Geotechnical Earthquake Engineering

Based on the review on the advances of several important problems in geotechnical seismic engineering, the authors propose the initial analysis theory of time-frequency-amplitude (known as TFA for short), in an effort to realize the organic combination of time and frequency information and develop a groundbreaking concept to the traditional idea in the geotechnical seismic engineering area

Ethanol oxidation activity and structure of carbon-supported Pt-modified PdSn-SnO2 influenced by different stabilizers

PdSn-SnO2 nanoparticles supported on Vulcan XC-72 carbon were synthesized by chemical reduction in the presence of three different stabilizing agents: ethylene diamine tetra-acetic acid (EDTA), sodium citrate (Nacitrate) and hexamethylenetetramine (HMTA). TEM analysis showed that PdSn-SnO2 /C catalyst made using the HMTA stabilizer produced the smallest particle size. XRD analysis detected the presence of PdSn alloy and the SnO2 phase in all three PdSn-SnO2 /C samples, and showed that PdSn-SnO2 (HMTA) had the smallest lattice parameter. After PdSn-SnO2 samples were modified by Pt, the particle size distribution and average size of nanoparticles of Pt-PdSn-SnO2 did not obviously change, and the fcc structure of PdSn in all three samples was retained. XPS measurement showed a higher upshift of Pt 4f binding energy occurred for Pt/PdSn-SnO2 /C (HMTA) compared to those of Pt/PdSn-SnO2 /C (EDTA) and Pt/PdSn-SnO2 /C (Nacitrate). Pt/PdSn-SnO2 /C (HMTA) was also found to have the highest CO and ethanol oxidation activity among the three catalysts.Web of Scienc

Durability of Polymer /Metal Interfaces Under Cyclic Loading

146 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.The mixed-mode was applied by a piezoelectric actuator. Subcritical crack growth was observed along the epoxy/aluminum interface and the growth rate was found to depend on the magnitude of the applied electric field. Kinetics of the crack growth was correlated with the piezoelectric driving force. The resulting crack growth behavior was compared with the results from the conventional mechanical testing technique. Large differences were found between these two methods. Using this newly developed technique, effects of loading mode and frequency were studied. The fatigue resistance was found to increase with the mode II component and was expressed as a function of the KII/K I ratio. A strong frequency effect was observed for the subcritical crack growth along the Al/Epoxy interface, their fatigue resistance increased with the testing frequency.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

The Ph Effect On Chemical Mechanical Planarization Of Copper

This study explores the effect of pH on the chemical mechanical polishing (CMP) characteristics of copper in H2O2 and KIO 3 based slurries under various dynamic and static conditions. High purity copper disc was used to study the dissolution and oxidation kinetics at various pH (2 to 10) with 5% H2O2 or 0.1M KIO 3. Electrochemical techniques were used to investigate the dissolution/passivation behavior of Cu. The affected surface layers of the statically etched Cu-disc were investigated using X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In 5% H 2O2, the Cu removal rate decreases with an increase in pH and reaches minimum at pH 6, and then increases under alkaline conditions. XPS results indicate that the surface oxide formed at various pH values was responsible for this CMP trend. However, with 0.1M KIO3, the CMP removal rates were found to be lower at pH 2. The maximum was observed at pH 4, then the removal rate decreased with the increase of pH. The lower value of removal rate at pH2 was due to the fast interaction between Cu and KIO 3 and the precipitation of CuI on the pad, which makes the pad glassy, resulting in lowered removal rates. This was confirmed by XPS measurements. The decreased CMP removal rates when the pH is higher than 4 might be due to the weaker oxidation power of KIO3 with the increase of pH

Identification and molecular cloning of novel antimicrobial peptides from skin secretions of Odorrana versabilis and Rana palustris

Objective: Amphibian skin secretions are an abundant source of bioactive peptides, some of which could be developed as candidate drugs. Among these natural peptides, cytolytic peptides have attracted the most attention given that they might replace conventional antibiotics and help deal with the problem of microbial resistance. This study discovered two bioactive peptides, Brevinin-1-PLr and Nigrocin-2-OV, from two species frogs, the Chinese bamboo leaf odorous frog (Odorrana versabilis) and the North American pickerel frog (Rana palustris), respectively. Their antimicrobial, anticancer and hemolytic activities were also investigated. Methods: cDNA sequences encoding peptides were cloned from cDNA libraries constructed from the lyophilized secretions of the Chinese bamboo leaf odorous frog and the North American pickerel frog. By reversed-phase HPLC and MS/MS fragmentation sequencing, the encoded novel peptides, named Nigrocin-2-OV and Brevinin-1-PLr, were identified in skin secretions and their structures were confirmed. Replicates of both peptides were produced through solid phase peptide synthesis. Their antimicrobial and anticancer activity was studied against three types of microorganisms (Staphylococcus aureus, Candida albicans, and Escherichia coli) and five cancer cell lines (NCI-H157, PC-3, MDA-MB-435s, MCF-7, and U251MG). Their hemolytic activity was investigated using whole horse blood. Results: In this research, cDNA sequences encoding two novel 24-mer peptides were cloned from cDNA libraries constructed from the lyophilized skin secretions of the Chinese bamboo leaf odorous frog and the North American pickerel frog. Both of the peptides had the strongest inhibitory effect against C. albicans, and IC50 values against five cancer cell lines were all under 6 μM. Conclusions: Nigrocin-2-OV and Brevinin-1-PLr had the strong ability to inhibit the proliferation of studied microorganisms and tumor cell lines, with slight hemolytic activity. Compared with Brevinin-1-PLr, Nigrocin-2-OV exhibited higher antimicrobial and anticancer activity but slightly higher hemolytic activity

Piezoelectric Actuation Of Crack Growth Along Polymer/Metal Interfaces In Adhesive Bonds

A new experimental technique for determining mechanical properties of the polymer/metal interface was developed by replacing the conventional mechanical testing machine with a piezoelectric actuator. The actuator was made from a thin ferroelectric ceramic beam attached to a bilayer polymer/metal composite specimen. The trilayer specimen was loaded by applying ac electric fields on the piezoelectric actuator to drive crack growth along the polymer/metal interface. Using this technique, fatigue crack growth behavior of epoxy/ aluminum interface was studied as a function of electric field, crack length and cyclic frequency. The crack growth rate was found to depend on the magnitude of the applied electric field and decrease with testing frequency

Chemical-Mechanical Planarization Of Copper: The Effect Of Inhibitor And Complexing Agent

The present investigation was focused on understanding of the oxidation, dissolution and modification of Cu surface in slurries at various pH using hydrogen peroxide as oxidizer, glycine as complexing agent and 3-amino-triazol (ATA) as inhibitor during Cu-CMP. The electrochemical process involved in the oxidative dissolution of copper was investigated by potentiodynamic polarization studies. Surface modification of copper was investigated using X-ray photoelectron spectroscopy to understand the interaction of Cu-H 2O2-glycine-ATA during CMP. In the absence of glycine and ATA, the copper removal rate is found to be high in a slurry with 5% H 2O2 at pH 2, then it decreases with increasing pH and reaches the minimum at pH 6, it continuously increases at alkaline condition. In the presence of 0.01M glycine, the removal rate of copper decreases in acidic slurries while increases significantly in alkaline slurries. With the further addition of ATA, the copper removal rate was reduced. However, better surface planarity was obtained. The present investigation enhanced understanding of the mechanism of Cu CMP in the presence of oxidizer, complexing agent and inhibitor for formulation of a highly effective CMP-slurry

Electrochemical Characterization Of Copper Chemical Mechanical Polishing

Chemical mechanical polishing (CMP) of copper was performed using H2O2 as oxidizer and alumina particles as abrasives. The interaction between the Cu surface and the slurry was investigated by potentiodynamic measurements taken during the polishing process as well as under static conditions. The Cu removal rate reached a maximum at 1% H2O2 concentration, and decreased with a further increase in H2O2 concentration. The static etch rate showed the same trend. Atomic force microscopic measurements were performed on both the etched surface and polished surface. It was shown that the surface roughness of the polished surface increased as the H2O2 concentration increased. This can be explained by changes in the structure of the passivating layer and the dominating role of the dynamic repassivation during polishing. © 2003 Elsevier B.V. All rights reserved

Effect Of Hydrogen Peroxide On Oxidation Of Copper In Cmp Slurries Containing Glycine And Cu Ions

This study compares the oxidative dissolution, passivation, and polishing behavior of copper chemical-mechanical polishing in the presence of hydrogen peroxide, glycine, and copper sulfate. High purity discs were used to study the dissolution and oxidation kinetics under static and dynamic conditions at pH 4 with varying H2O2 concentrations. Changes in surface chemistry of the statically etched copper disc were investigated using X-ray photoelectron spectroscopy (XPS). In the presence of H2O 2, the copper removal rate reached a maximum at 1% H 2O2 concentration, and decreased with further increase in H2O2 concentration. Electrochemical studies indicate a strong passivation process at higher H2O2 concentrations due to the rapid formation of oxide on the surface. With the further addition of glycine and copper sulfate to the slurry, the copper removal rates increased significantly and the maximum removal rate shifted to a H2O 2 concentration of 3%. Electrochemical investigation indicates an enhanced dissolution of copper, which might be due to the strong catalytic activity of Cu(II)-glycine complexes in decomposing H2O2 to yield hydroxyl radicals. XPS results suggest that the passivation at higher H2O2 concentrations in the presence of glycine and copper sulfate is provided by the OH radicals adsorbed on Cu surface. © 2004 Elsevier Ltd. All rights reserved