Morphological features and nanostructures generated during SiC graphitization process

Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect fabrication of high-quality epitaxial graphene on semiconductor substrates.In this work,we investigate the surface morphologies and atomic structures during graphitization process of 4H-SiC(0001) using scanning tunneling microscopy.Our high-magnified scanning-tunneling-microscope images exhibit the appearance and gradual developments of SiC(1 × 1)nanostructures after 1100℃ cleaning treatments,irregularly distributed among carbon nanocaps and(√3×√3) reconstruction domains.A model for the formation and growth progression of SiC(1 × 1) nanostructures has been proposed.When post-annealing temperature reaches 1300 ℃,the nanoholes and nanoislands can be observed on the surface,and multilayer graphene is often detected lying on the top surface of those nanoislands.These results provide profound insights into the complex evolution process of surface morphology during SiC thermal decomposition and will shed light on fabrication of SiC nanostructures and graphene nanoflakes.

Er intercalation and its impact on transport properties of epitaxial graphene

Intercalation of atomic species is a practicable method for epitaxial graphene to adjust the electronic band structure and to tune the coupling between graphene and Si C substrate. In this work, atomically flat epitaxial graphene is prepared on 4H-SiC(0001) using the flash heating method in an ultrahigh vacuum system. Scanning tunneling microscopy, Raman spectroscopy and electrical transport measurements are utilized to investigate surface morphological structures and transport properties of pristine and Er-intercalated epitaxial graphene. It is found that Er atoms are intercalated underneath the graphene layer after annealing at 900℃, and the intercalation sites of Er atoms are located mainly at the bufferlayer/monolayer-graphene interface in monolayer domains. We also report the different behaviors of Er intercalation in monolayer and bilayer regions, and the experimental results show that the diffusion barrier for Er intercalated atoms in the buffer-layer/monolayer interface is at least 0.2 eV higher than that in the first/second graphene-layer interface. The appearance of Er atoms is found to have distinct impacts on the electronic transports of epitaxial graphene on SiC(0001).

A Particle Method for the b-Equation

In this paper, we apply the particle method to solve the numerical solution of a family of non-li-near Evolutionary Partial Differential Equations. It is called b-equation because of its bi-Hamiltonian structure. We introduce the particle method as an approximation of these equations in Lagrangian representation for simulating collisions between wave fronts. Several numerical examples will be set to illustrate the feasibility of the particle method.

miR-133b targets NCAPH to promote β-catenin degradation and reduce cancer stem cell maintenance in non-small cell lung cancer

Dear Editor,Non-small cell lung cancer(NSCLC),one of the most common lung cancers,is well known to have diverse pathological features.Cancer stem cells(CSCs)have been identified to play critical roles in tumor metastasis and drug resistance,while its potential clinical significance and molecular mechanism are still unclear.In addition,numerous findings have also shown that miRNAs play pivotal roles in CSCs during tumor progression.

iBIG:An Integrative Network Tool for Supporting Human Disease Mechanism Studies

Understanding the mechanism of complex human diseases is a major scientitic challenge. Towards this end, we developed a web-based network tool named iBIG （stands for integrative BioloGy）, which incorporates a variety of information on gene interaction and regulation. The generated network can be annotated with various types of information and visualized directly online. In addition to the gene networks based on physical and pathway interactions, networks at a functional level can also be constructed. Furthermore, a supplementary R package is provided to process microarray data and generate a list of important genes to be used as input for iBIG. To demonstrate its usefulness, we collected 54 microarrays on common human diseases including cancer, neurolog- ical disorders, infectious diseases and other common diseases. We processed the microarray data with our R package and constructed a network of functional modules perturbed in common human diseases. Networks at the functional level in combination with gene networks may provide new insight into the mechanism of human diseases, iBIG is freely available at http：//lei.big.ac.cn/ibig.

Live microbial cells adsorb Mg2＋ more effectively than lifeless organic matter

The Mg2＋ content is essential in determining different Mg-CaCO3 minerals. It has been demonstrated that both microbes and the organic matter secreted by microbes are capable of allocating Mg2＋ and Ca2＋ during the formation of Mg-CaCO3, yet detailed scenarios remain unclear. To investigate the mechanism that microbes and microbial organic matter potentially use to mediate the allocation of Mg2＋ and Ca2＋ in inoculating systems, microbial mats and four marine bacterial strains （Synecho- coccus elongatus, Staphylococcus sp., Bacillus sp., and Desulfovibrio vulgaris） were incubated in artificial sea- water media with Mg/Ca ratios ranging from 0.5 to 10.0. At the end of the incubation, the morphology of the microbial mats and the elements adsorbed on them were analyzed using scanning electronic microscopy （SEM） and energy diffraction spectra （EDS）, respectively. The content of Mg2＋ and Ca2＋ adsorbed by the extracellular polysaccharide substances （EPS） and cells of the bacterial strains were analyzed with atomic adsorption spectroscopy （AAS）. The functional groups on the surface of the cells and EPS of S. elongatus were estimated using automatic potentiometric titration combined with a chemical equilibrium model. The results show that live microbial mats generally adsorb larger amounts of Mg2＋ than Ca2＋, while this rarely is the case for autoclaved microbial mats. A similar phenomenon was also observed for the bacterial strains. The living cells adsorb more Mg2＋ than Ca2＋, yet a reversed trend was observed for EPS. The functional group analysis indicates that the cell surface of S. elongatus contains more basic functional groups （87.24%）, while the EPS has more acidic and neutral functional groups （83.08%）. These features may be responsible for the different adsorption behavior of Mg2＋ and Ca2＋ by microbial cells and EPS. Our work confirms the differ-ential Mg2＋ and Ca2＋ mediation by microbial cells and EPS, which may provide insight into the processes that microbes use to induce Mg-carbonate formation.