The structure and infrastructure of the global nanotechnology literature

Text mining is the extraction of useful information from large volumes of text. A text mining analysis of the global open nanotechnology literature was performed. Records from the Science Citation Index (SCI)/Social SCI were analyzed to provide the infrastructure of the global nanotechnology literature (prolific authors/journals/institutions/countries, most cited authors/papers/journals) and the thematic structure (taxonomy) of the global nanotechnology literature, from a science perspective. Records from the Engineering Compendex (EC) were analyzed to provide a taxonomy from a technology perspective.

• The Far Eastern countries have expanded nanotechnology publication output dramatically in the past decade.
• The Peoples Republic of China ranks second to the USA (2004 results) in nanotechnology papers published in the SCI, and has increased its nanotechnology publication output by a factor of 21 in a decade.
• Of the six most prolific (publications) nanotechnology countries, the three from the Western group (USA, Germany, France) have about eight percent more nanotechnology publications (for 2004) than the three from the Far Eastern group (China, Japan, South Korea).
• While most of the high nanotechnology publication-producing countries are also high nanotechnology patent producers in the US Patent Office (as of 2003), China is a major exception. China ranks 20th as a nanotechnology patent-producing country in the US Patent Office.

     

Coded excitation using biphase-coded pulse with mismatched filters for high-frequency ultrasound imaging

A scheme of using phase-coded excitation and mismatched filter compression for high-frequency ultrasound imaging is presented in this paper. Biphase-coded pulses were constructed to excite the transducer. Received signals were compressed with mismatched filters optimized by minimizing peak-sidelobe-level (PSL). Both simulation and experiments were carried out to demonstrate the advantage of this technique. The simulation results demonstrated a possible sidelobe reduction (<-90 dB) with a slightly decrease of the signal-to-noise ratio of less than 1 dB compared with the compression using matched filters alone. The experimental results showed about 14 dB SNR improvement as well as -40 dB sidelobe level when the Barker-13 code excitation with 3-cycle sinusoidal wave carrier was used.     

An outside-in approach to adjacent bistetrahydrofuran annonaceous acetogenins with C2 core symmetry. Total synthesis of asimicin and a C32 analogue

[reaction: see text] A synthesis of the Annonaceous acetogenin asimicin and a side-chain analogue has been achieved by a highly convergent route in which Grubbs cross-metathesis plays a key role.     

Regioselective dicouplings: application to differentially substituted pyrroles

[reaction: see text] In an effort to develop a more concise route to differentially substituted pyrroles (such as that found in the lamellarins), a completely regioselective one-pot double Suzuki coupling has been discovered. The key feature is the use of a ligand-free palladium catalyst under optimized conditions, which results only in coupling of the C5 bromide. At this point, addition of a second boronic acid and a phosphine ligand enables coupling at the remaining C4 bromide.     

A three-dimensional framework structure constructed from 2-(2-pyridyl-N-oxide) ethylphosphonic acid and Nd(III)

A multistep synthesis for 2-(2-pyridyl-N-oxide) ethylphosphonic acid 6-H2 is described along with its spectroscopic (IR, NMR) data and a single-crystal X-ray diffraction structure analysis. Combination of the ligand with Nd(OH)3 results in the formation of a complex Nd(6-H)3. Single-crystal X-ray diffraction analysis reveals a three-dimensional crystal network generated by hydrogen-bonded chains along the crystallographic c axis. The hydrogen bonds are formed between phosphonic acid anion (6-H)(-1) protons on one chain and pyridyl N-oxide oxygen atoms in neighboring chains. The asymmetric unit contains 1/3[Nd(6-H)3] and there are two unique Nd(III) atoms, each with point symmetry. As a result, each Nd(III) ion is bound to six (6-H)(-1) ligands and the symmetry about the Nd(III) ion is octahedral with each vertex occupied by a phosphonate oxygen atom. The Nd-O bond lengths are essentially identical: Nd(1)-O(3), 2.336 (1) A; Nd(2)-O(4), 2.340 (1) A. The monoanionic ligand (6-H)(-1), therefore, serves to bridge the unique Nd(III) centers.     

Isometric embeddings of \mathbb{Z}_{p^k} in the Hamming space \mathbb{F}_{p}^{N} and \mathbb{Z}_{p^k}-linear codes

Isometric embeddings of $\mathbb{Z}_{p^n+1}$ into the Hamming space ( $\mathbb{F}_{p}^{p^n},w$ ) have played a fundamental role in recent constructions of non-linear codes. The codes thus obtained are very good codes, but their rate is limited by the rate of the first-order generalized Reed–Muller code—hence, when n is not very small, these embeddings lead to the construction of low-rate codes. A natural question is whether there are embeddings with higher rates than the known ones. In this paper, we provide a partial answer to this question by establishing a lower bound on the order of a symmetry of ( $\mathbb{F}_{p}^{N},w$ ).     

Cross-phase modulation imaging

We demonstrate a cross-phase modulation measurement technique based on the sensitive detection of modulation transfer in a pump-probe setup. By modulating the amplitude of the pump beam and spectrally analyzing the probe beam, we achieve a rapid, background-free measurement of nonlinear phase modulation using power levels acceptable in biological imaging. This measurement technique would allow the extension of widely employed phase microscopy methods to the nonlinear regime, providing intrinsic and universal nonlinear contrast for biological imaging.     

Single-shot dual-energy x-ray imaging with a flat-panel sandwich detector for preclinical imaging

We describe a multi-layer (“sandwich”) configuration detector consisting of two x-ray imaging flat-panel detectors for single-shot (single-kV) dual-energy imaging. An intermediate copper filter is used to increase spectral separation between the two detectors to improve contrast at the expense of image noise. Monte Carlo and cascaded-systems analyses of the signal and noise performance are described that quantify performance characteristics. Image quality of dual-energy images obtained from a prototype sandwich-detector system is evaluated using a figure of merit (FOM), defined as the squared contrast-to-noise ratio normalized by x-ray exposure for a mouse phantom for preclinical imaging. Demonstration dual-energy bone and soft-tissues images of a postmortem mouse are obtained using the prototype system. While the FOM with the single-shot detector is lower than that achieved using a conventional dual-shot (dual-kV) method, the single-shot approach may be preferable when imaging speed or insensitivity to motion artifacts is a primary concern.