Proximity and anomalous field-effect characteristics in double-wall carbon nanotubes

Proximity effect on field-effect characteristic (FEC) in double-wall carbon nanotubes (DWCNTs) is investigated. In a semiconductor-metal (S-M) DWCNT, the penetration of electron wavefunctions in the metallic shell to the semiconducting shell turns the original semiconducting tube into a metal with a non-zero local density of states at the Fermi level. By using a two-band tight-binding model on a ladder of two legs, it is demonstrated that anomalous FEC observed in so-called S-M type DWCNTs can be fully understood by the proximity effect of metallic phases.Comment: 4 pages, 4 figure

Processing of G4 DNA by Dna2 Helicase/nuclease and RPA provides insights into the mechanism of Dna2/RPA substrate recognition

The polyguanine-rich DNA sequences commonly found at telomeres and in rDNA arrays have been shown to assemble into structures known as G quadruplexes, or G4 DNA, stabilized by base-stacked G quartets, an arrangement of four hydrogen-bonded guanines. G4 DNA structures are resistant to the many helicases and nucleases that process intermediates arising in the course of DNA replication and repair. The lagging strand DNA replication protein, Dna2, has demonstrated a unique localization to telomeres and a role in de novo telomere biogenesis, prompting us to study the activities of Dna2 on G4 DNA-containing substrates. We find that yeast Dna2 binds with 25-fold higher affinity to G4 DNA formed from yeast telomere repeats than to single-stranded DNA of the same sequence. Human Dna2 also binds G4 DNAs. The helicase activities of both yeast and human Dna2 are effective in unwinding G4 DNAs. On the other hand, the nuclease activities of both yeast and human Dna2 are attenuated by the formation of G4 DNA, with the extent of inhibition depending on the topology of the G4 structure. This inhibition can be overcome by replication protein A. Replication protein A is known to stimulate the 5'- to 3'-nuclease activity of Dna2; however, we go on to show that this same protein inhibits the 3'- to 5'-exo/endonuclease activity of Dna2. These observations are discussed in terms of possible roles for Dna2 in resolving G4 secondary structures that arise during Okazaki fragment processing and telomere lengthening

Critical assessment indicators for measuring benefits of rural infrastructure investment in China

Rural infrastructure is of vital importance for agricultural growth, economic development, and poverty alleviation, particularly in developing countries such as China. In line with the implementation of a Coordinated Urban-Rural Development Strategy, infrastructure investment in China has consciously been tilted to rural areas. An urgent need exists to assess whether the investment has induced the benefits as expected. Existing research on rural infrastructure investment assessment focuses primarily on economic return while neglecting its social and ecological benefits. This paper identifies a set of critical assessment indicators (CAIs) that can be used to evaluate the multifaceted benefits of rural infrastructure investment in China. Research data were collected through a questionnaire survey given to three groups of experts, including government officers, professionals, and business practitioners who are working in China's housing and urban-rural development sector. Monte Carlo simulation (MCS) is used to generate additional data to supplement the data set from the questionnaire survey. The fuzzy set theory, which appreciates the fuzziness of data from the questionnaire survey, is used in the selection of CAIs. The CAIs can help the local governments in China to make better decisions in investing in rural infrastructure. These critical indicators can also be generalized to provide valuable references for the investigations of rural infrastructure investment in other developing countries. © 2011 American Society of Civil Engineers.postprin

Study on analyzing questionnaire survey by Monte Carlo Simulation

Traditional questionnaire usually takes likert scale and treats the data as discrete and controllable. It overlooks the different opinions chosen in the same scale, moreover does not consider the possibility distribution trend. Monte Carlo Simulation (MCS) is used to explore into the possible trend based on the distribution from the questionnaire. The difference of the results based on original questionnaire and MCS show the trying is beneficial and interesting. However, for this method, the questionnaire survey should be scientifically random. Moreover, foundational research should be conducted to test the validity. © 2010 IEEE.published_or_final_versio

Spin-orbit scattering in quantum diffusion of massive Dirac fermions

Effect of spin-orbit scattering on quantum diffusive transport of two-dimensional massive Dirac fermions is studied by the diagrammatic technique. The quantum diffusion of massive Dirac fermions can be viewed as a singlet Cooperon in the massless limit and a triplet Cooperon in the large-mass limit. The spin-orbit scattering behaves like random magnetic fields only to the triplet Cooperon, and suppresses the weak localization of Dirac fermions in the large-mass regime. This behavior suggests an experiment to detect the weak localization of bulk subbands in topological insulator thin films, in which a narrowing of the cusp of the negative magnetoconductivity is expected after doping heavy-element impurities. Finally, a detailed comparison between the conventional two-dimensional electrons and Dirac fermions is presented for impurities of orthogonal, symplectic, and unitary symmetries.Comment: 5 pages, 3 figures, 2 tables. To be submitted, comments are welcom

Variation of the Fine-Structure Constant from the de Sitter Invariant Special Relativity

There are obvious discrepancies among various experimental constraints on the variation of the fine-structure constant, $\alpha$. We attempt to discuss the issue in the framework of de Sitter invariant Special Relativity (${\cal SR}_{c,R}$) and to present a possible solution to the disagreement. In addition, on the basis of the observational data and the discussions presented in this Letter, we derive a rough theoretical estimate of the radius of the Universe.Comment: 8 pages, no figure

Benchmarking construction waste management performance using big data

The waste generation rate (WGR) is usually used as a key performance indicator (KPI) to benchmark construction waste management (CWM) performance, with a view to improving the performance con- tinuously. However, existing researches, for different reasons, only investigated a relatively small amount of construction projects, whose WGRs cannot be confidently accepted as KPIs. This study develops a set of more reliable KPIs/WGRs using an available big dataset on CWM in Hong Kong. By mining the 2,212,026 waste disposal records generated from 5764 projects in two consecutive years of 2011 and 2012, the WGRs/KPIs are revisited and refined. Demolition is found the most wasteful works. New building, and maintenance and renovation (M&R) works individually produce the least waste amount but by accumu- lating all M&R works, their contribution to the total amount of construction waste could be phenomenal. Based on the more reliable WGRs from the big data, CWM performance benchmarks for different cate- gories of projects are set up. A contractor can benchmark its CWM performance against its counterparts or its past performance as ‘Good’, ‘Average’, and ‘Not-so-good’, and thus identify better CWM practices that induce superior performance. Based on the benchmarks, the government may consider setting up a WGR-step toll system to encourage those ‘Not-so-good’ contractors to perform well in the future, and initiate incentives to the companies conducting ‘Good’ projects to spur better CWM performance. Overall, the WGRs derived from the big data and more robust analyses provide a very powerful and handy tool for CWM

Developmental definition of MSCs: New insights into pending questions

Mesenchymal stem cells (MSCs) are a rare heterogeneous population of multipotent cells that can be isolated from many different adult and fetal tissues. They exhibit the capacity to give rise to cells of multiple lineages and are defined by their phenotype and functional properties, such as spindle-shaped morphology, adherence to plastic, immune response modulation capacity, and multilineage differentiation potential. Accordingly, MSCs have a wide range of promising applications in the treatment of autoimmune diseases, tissue repair, and regeneration. Recent studies have shed some light on the exact identity and native distribution of MSCs, whereas controversial results are still being reported, indicating the need for further review on their definition and origin. In this article, we summarize the important progress and describe some of our own relevant work on the developmental definition of MSCs. © 2011 Mary Ann Liebert, Inc.published_or_final_versio

A modified layer-removal method for residual stress measurement in electrodeposited nickel films

Combining the traditional layer-removal method with a cantilever beam model, a modified layer-removal method is developed and used to measure residual stress in single and multi-layer electrodeposited nickel films with thickness of 2.5 μm. The out-of-plane displacement of the free tip of a cantilever beam is measured by the digital speckle correlation method. The results show that residual stress in a single semimat nickel film is compressive, while in a multi-layer system composed of dark, semimat and holophote nickel, residual stress in the surface layer is tensile. Residual stress decreases gradually with the increase of etching depths of single and multi-layer films. These findings are in qualitative agreement with nanoindentation tests, which confirms the reliability of the modified layer-removal method