Simulation and characterisation of electroplated micro-copper columns for electronic interconnection

Growth mechanism of electroplated copper columns has been systematically studied by simulations and characterizations. A two-dimensional cross-sectional kinetic Monte Carlo (2DCS-KMC) model has been developed to simulate the electrodeposition of single crystal copper. The evolution of the microstructure has been visualized. The cluster density, average cluster size, variance of the cluster size and average aspect ratio were obtained from the simulations. The growth history of the deposition from the first atom to an equivalent of 100 monolayers was reconstructed. Following the single-lattice 2DCS-KMC model for a single crystal, a two-dimensional cross-sectional poly-lattice kinetic Monte Carlo (2DCSP-KMC) model has been developed for simulation of the electrodeposition of polycrystalline copper on both a copper and a gold substrate. With this model, the early-stage nucleation and the grain growth after impingement of nuclei can be simulated; as such the entire growth history is reconstructed in terms of the evolution of microstructure, grain statistics and grain boundary misorientation. The model is capable of capturing some key aspects of nucleation and growth mechanisms including the nucleation type (e.g. homogeneous or heterogeneous), texture development, the growth of grains and higher energetic state of grain boundaries. The model has also proven capable of capturing the effects of deposition parameters including applied electrode potential, concentration of cupric ions and temperature. Their effects are largely dependent on the substrates. The early-stage electrocrystallization of Cu on polycrystalline Au has been studied by ex-situ AFM observations. The evolution of surface morphology of the electrodeposited copper on a sputtered Au seed layer from 16ms to 1000s was observed and their formation mechanism discussed. The heterogeneous nucleation phenomenon, the competitive growth both longitudinally and laterally, and the dominant growth of some nuclei were experimentally observed, which are also visualized by the relevant KMC simulation results at a smaller size scale and a shorter time scale. A heuristic model is therefore proposed to describe the mechanism of the early-stage electrocrystallization of Cu on a polycrystalline Au seed layer. Electroplated copper columns plated for different times have been characterized in terms of the evolution of their external morphology, cross-sectional microstructure and crystal structure. The microstructure of electroplated copper columns is characteristic of bi-modal or tri-modal grain size distribution. The results indicate that recrystallization has occurred during or after the plating, top-down and laterally. Slight changes of the crystal structure were observed by in-situ XRD and it was found that the changes of the (111) and (200) planes occurred at different stages of self-annealing. Finally, the results indicate the presence of organic additives is not essential for self-annealing of a copper column to occur

A perceptually validated model for surface depth hallucination

Capturing detailed surface geometry currently requires specialized equipment such as laser range scanners, which despite their high accuracy, leave gaps in the surfaces that must be reconciled with photographic capture for relighting applications. Using only a standard digital camera and a single view, we present a method for recovering models of predominantly diffuse textured surfaces that can be plausibly relit and viewed from any angle under any illumination. Our multiscale shape-from-shading technique uses diffuse-lit/flash-lit image pairs to produce an albedo map and textured height field. Using two lighting conditions enables us to subtract one from the other to estimate albedo. In the absence of a flash-lit image of a surface for which we already have a similar exemplar pair, we approximate both albedo and diffuse shading images using histogram matching. Our depth estimation is based on local visibility. Unlike other depth-from-shading approaches, all operations are performed on the diffuse shading image in image space, and we impose no constant albedo restrictions. An experimental validation shows our method works for a broad range of textured surfaces, and viewers are frequently unable to identify our results as synthetic in a randomized presentation. Furthermore, in side-by-side comparisons, subjects found a rendering of our depth map equally plausible to one generated from a laser range scan. We see this method as a significant advance in acquiring surface detail for texturing using a standard digital camera, with applications in architecture, archaeological reconstruction, games and special effects. © 2008 ACM

Cryo-electron tomography of periplasmic flagella in Borrelia burgdorferi reveals a distinct cytoplasmic ATPase complex.

Periplasmic flagella are essential for the distinct morphology and motility of spirochetes. A flagella-specific type III secretion system (fT3SS) composed of a membrane-bound export apparatus and a cytosolic ATPase complex is responsible for the assembly of the periplasmic flagella. Here, we deployed cryo-electron tomography (cryo-ET) to visualize the fT3SS machine in the Lyme disease spirochete Borrelia burgdorferi. We show, for the first time, that the cytosolic ATPase complex is attached to the flagellar C-ring through multiple spokes to form the “spoke and hub� structure in B. burgdorferi. This structure not only strengthens structural rigidity of the round-shaped C-ring but also appears to rotate with the C-ring. Our studies provide structural insights into the unique mechanisms underlying assembly and rotation of the periplasmic flagella and may provide the basis for the development of novel therapeutic strategies against several pathogenic spirochetes

Vegetation data of Songnen grassland in China

Include veagetation data of the original source of replicate plots and different treatments, such as plant species richness, Shannon-Wiener index,Pielou's index , density, height, coverage, and aboveground biomass

Gold-Catalyzed Cyclizations of (<i>o</i>‑Alkynyl)phenoxyacrylates with External Nucleophiles: Regio- and Stereoselective Synthesis of Functionalized Benzo[<i>b</i>]oxepines

A catalytic approach to benzo[<i>b</i>]oxepines with high stereoselectivity by Au-catalyzed cyclization of (<i>o</i>-alkynyl)phenoxyacrylates with various nucleophiles under mild reaction conditions has been developed. Notably, the use of vinyl ether instead of alcohol could afford the same benzoxepines. The reaction may proceed by Au-catalyzed oligomerization of vinyl ether to release the alcohol, which then reacts with (<i>o</i>-alkynyl)phenoxyacrylates to furnish the benzoxepines

Gold-Catalyzed Cyclizations of (<i>o</i>‑Alkynyl)phenoxyacrylates with External Nucleophiles: Regio- and Stereoselective Synthesis of Functionalized Benzo[<i>b</i>]oxepines

A catalytic approach to benzo[<i>b</i>]oxepines with high stereoselectivity by Au-catalyzed cyclization of (<i>o</i>-alkynyl)phenoxyacrylates with various nucleophiles under mild reaction conditions has been developed. Notably, the use of vinyl ether instead of alcohol could afford the same benzoxepines. The reaction may proceed by Au-catalyzed oligomerization of vinyl ether to release the alcohol, which then reacts with (<i>o</i>-alkynyl)phenoxyacrylates to furnish the benzoxepines

Gold-Catalyzed Cyclizations of (<i>o</i>‑Alkynyl)phenoxyacrylates with External Nucleophiles: Regio- and Stereoselective Synthesis of Functionalized Benzo[<i>b</i>]oxepines

A catalytic approach to benzo[<i>b</i>]oxepines with high stereoselectivity by Au-catalyzed cyclization of (<i>o</i>-alkynyl)phenoxyacrylates with various nucleophiles under mild reaction conditions has been developed. Notably, the use of vinyl ether instead of alcohol could afford the same benzoxepines. The reaction may proceed by Au-catalyzed oligomerization of vinyl ether to release the alcohol, which then reacts with (<i>o</i>-alkynyl)phenoxyacrylates to furnish the benzoxepines

Gold-Catalyzed Cyclizations of (<i>o</i>‑Alkynyl)phenoxyacrylates with External Nucleophiles: Regio- and Stereoselective Synthesis of Functionalized Benzo[<i>b</i>]oxepines

A catalytic approach to benzo[<i>b</i>]oxepines with high stereoselectivity by Au-catalyzed cyclization of (<i>o</i>-alkynyl)phenoxyacrylates with various nucleophiles under mild reaction conditions has been developed. Notably, the use of vinyl ether instead of alcohol could afford the same benzoxepines. The reaction may proceed by Au-catalyzed oligomerization of vinyl ether to release the alcohol, which then reacts with (<i>o</i>-alkynyl)phenoxyacrylates to furnish the benzoxepines

Molecular dynamics calculation of thermodynamic properties of iron solidification

The aim of this study is to identify the best available inter-atomic potentials for molecular dynamics (MD) calculation of solidification of iron and then to use the best potential to calculate thermodynamic properties such as equilibrium melting temperature, enthalpy, heat capacity and solid-liquid interfacial free energy. Our study reveals that embedded atom method (EAM) potential developed by Ackland et al. [2004 J. Phys.: Condens Matter. 16 S2629] appears to be the most accurate model for MD simulation of iron solidification. Simulations with the above EAM model predict the equilibrium melting temperature of iron is 1790K, the solid-liquid interfacial energy 214 mJ/m2. The difference with the experimental data is 1.2%, and 4.9% respectively

Contribution of Selenocysteine to the Peroxidase Activity of Selenoprotein S

Selenoprotein S (SelS, VIMP) is an intrinsically disordered enzyme that utilizes selenocysteine to catalyze the reduction of disulfide bonds and peroxides. Here it is demonstrated that selenocysteine is the residue oxidized by the peroxide substrate. It is possible to trap the reaction intermediate selenenic acid when the resolving cysteine is mutated. The selenocysteine allows SelS to rapidly re-form its selenenylsulfide bond following its reduction, and to resist inactivation by H₂O₂. We propose that SelS’s peroxidase mechanism is similar to that of atypical 2-Cys peroxiredoxin and that selenocysteine allows SelS to sustain activity under oxidative stress