Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator Bi2Se3 with scanning tunneling spectroscopy

Scanning tunneling spectroscopic studies of Bi2Se3 epitaxial films on Si (111) substrates reveal highly localized unitary impurity resonances associated with non-magnetic quantum impurities. The strength of the resonances depends on the energy difference between the Fermi level ({E_F}) and the Dirac point ({E_D}) and diverges as {E_F} approaches {E_D}. The Dirac-cone surface state of the host recovers within ~ 2{\AA} spatial distance from impurities, suggesting robust topological protection of the surface state of topological insulators against high-density impurities that preserve time reversal symmetry.Comment: 6 pages, 6 figures. Accepted for fast-track publication in Solid State Communications (2012

Finding the pitfalls in query performance

Despite their popularity, database benchmarks only highlight a small part of the capabilities of any given system. They do not necessarily highlight problematic components encountered in real life or provide hints for further research and engineering.In this paper we introduce discriminative performance benchmarking, which aids in exploring a larger search space to find performance outliers and their underlying cause. The approach is based on deriving a domain specific language from a sample query to identify a query workload. SQLscalpel subsequently explores the space using query morphing, and simulated annealing to find performance outliers, and the query components responsible. To speedup the exploration for often time-consuming experiments SQLscalpel has been designed to run asynchronously on a large cluster of machines.</p

Bacterial diversity in the intestine of sea cucumber Stichopus japonicus

The intestinal bacterial diversity of Stichopus japonicus was investigated using 16S ribosomal RNA gene (rDNA) clone library and Polymerase Chain Reaction/Denaturing Gradient Gel Electrophoresis (PCR-DGGE). The clone library yielded a total of 188 clones, and these were sequenced and classified into 106 operational taxonomic units (OTUs) with sequence similarity ranging from 88 to 100%. The coverage of the library was 77.4%, with approximately 88.7% of the sequences affiliated to Proteobacteria. Gammaproteobacteria and Vibrio sp. were the predominant groups in the intestine of S. japonicus. Some bacteria such as Legionella sp., Brachybacterium sp., Streptomyces sp., Propionigenium sp. and Psychrobacter sp were first identified in the intestine of sea cucumber

Integrating Al with NiO nano honeycomb to realize an energetic material on silicon substrate

Nano energetic materials offer improved performance in energy release, ignition, and mechanical properties compared to their bulk or micro counterparts. In this study, the authors propose an approach to synthesize an Al/NiO based nano energetic material which is fully compatible with a microsystem. A two-dimensional NiO nano honeycomb is first realized by thermal oxidation of a Ni thin film deposited onto a silicon substrate by thermal evaporation. Then the NiO nano honeycomb is integrated with an Al that is deposited by thermal evaporation to realize an Al/NiO based nano energetic material. This approach has several advantages over previous investigations, such as lower ignition temperature, enhanced interfacial contact area, reduced impurities and Al oxidation, tailored dimensions, and easier integration into a microsystem to realize functional devices. The synthesized Al/NiO based nano energetic material is characterized by scanning electron microscopy, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry

SciQL, Bridging the Gap between Science and Relational DBMS

Scientific discoveries increasingly rely on the ability to efficiently grind massive amounts of experimental data using database technologies. To bridge the gap between the needs of the Data-Intensive Research fields and the current DBMS technologies, we propose SciQL (pronounced as ‘cycle’), the first SQL-based query language for scientific applications with both tables and arrays as first class citizens. It provides a seamless symbiosis of array-, set- and sequence- interpretations. A key innovation is the extension of value-based grouping of SQL:2003 with structural grouping, i.e., fixed-sized and unbounded groups based on explicit relationships between elements positions. This leads to a generalisation of window-based query processing with wide applicability in science domains. This paper describes the main language features of SciQL and illustrates it using time-series concepts

SQALPEL: A database performance platform

Despite their popularity, database benchmarks only highlight a small fraction of the capabilities of any given DBMS. They often do not highlight problematic components encountered in real life database applications or provide hints for further research and engineering. To alleviate this problem we coined discriminative performance benchmarking as the way to go. It aids in exploring a larger query search space to find performance outliers and their underlying cause. The approach is based on deriving a domain specific language from a sample complex query to identify and execute a query workload. The demo illustrates sqalpel, a complete platform to collect, manage and selectively disseminate performance facts, that enables repeatability studies, and economy of scale by sharing performance experiences

SciQL, A query language for science applications

Scientific applications are still poorly served by contemporary relational database systems. At best, the system provides a bridge towards an external library using user-defined functions, explicit import/export facilities or linked-in Java/C# interpreters. Time has come to rectify this with SciQL, a SQL-query language for science applications with arrays as first class citizens. It provides a seamless symbiosis of array-, set-, and sequence- interpretation using a clear separation of the mathematical object from its underlying storage representation. The language extends value-based grouping in SQL with structural grouping, i.e., fixed-sized and unbounded groups based on explicit relationships between its index attributes. It leads to a generalization of window-based query processing. The SciQL architecture benefits from a column store system with an adaptive storage scheme, including keeping multiple representations around for reduced impedance mismatch. This paper is focused on the language features, its architectural consequences and extensive examples of its intended use

Magnetospectroscopy of epitaxial few-layer graphene

The inter-Landau level transitions observed in far-infrared transmission experiments on few-layer graphene samples show a behaviour characteristic of the linear dispersion expected in graphene. This behaviour persists in relatively thick samples, and is qualitatively different from that of thin samples of bulk graphite.Comment: Invited short review to appear in a special issue of Solid State Communication