The Effect of Nanoscale Confinement on the Collective Electron Transport Behavior in Au Nanoparticles Self‐Assembled in a Nanostructured Polystyrene‐block‐poly(4‐vinylpyridine) Diblock Copolymer Ultra‐thin Film

This study involves the collective electron transport behavior of sequestered Au nanoparticles in a nanostructured polystyrene‐block‐poly(4‐vinylpyridine). The monolayer thin films (ca. 30 nm) consisting of Au nanoparticles self‐assembled in the 30‐nm spherical poly(4‐vinylpyridine) domains of an polystyrene‐block‐poly(4‐vinylpyridine) diblock copolymer were prepared. From the current‐voltage characteristics of these thin films, the collective electron transport behavior of Au nanoparticles sequestered in the spherical poly(4‐vinylpyridine) nanodomains was found to be dictated by Coulomb blockade and was quasi one‐dimensional, as opposed to the three‐dimensional behavior displayed by Au nanoparticles that had been dispersed randomly in homo‐poly(4‐vinylpyridine). The threshold voltage of these composite increased linearly upon increasing the inter‐nanoparticle distance. The electron tunneling rate constant in the case of Au nanoparticles confined in poly(4‐vinylpyridine) nanodomains is eight times larger than that in the randomly distributed case and it increases upon increasing the amount of Au nanoparticles. This phenomenon indicates that manipulating the spatial arrangement of metal nanoparticles by diblock copolymer can potentially create electronic devices with higher performance.     

A Review of Reliability Research on Nanotechnology

Nano-reliability measures the ability of a nano-scaled product to perform its intended functionality. At the nano scale, the physical, chemical, and biological properties of materials differ in fundamental, valuable ways from the properties of individual atoms, molecules, or bulk matter. Conventional reliability theories need to be restudied to be applied to nano-engineering. Research on nano-reliability is extremely important due to the fact that nano-structure components account for a high proportion of costs, and serve critical roles in newly designed products. This review introduces the concepts of reliability to nano-technology; and presents the current work on identifying various physical failure mechanisms of nano-structured materials, and devices during fabrication process, and operation. Modeling techniques of degradation, reliability functions, and failure rates of nano-systems are also reviewed in this work.     

High Tg and high organosolubility of novel unsymmetric polyimides

A series of new polyimides (PIs) containing di‐tert‐butyl side groups were synthesized via a polycondensation of 1‐(4‐aminophenoxy)‐4‐(4‐amino‐2‐methylphenyl)‐2,6‐di‐tert‐butylbenzene ( 3 ) with various aromatic tetracarboxylic dianhydrides. The novel unsymmetric PIs exhibited a low dielectric constants (2.78–3.02), low moisture absorption (0.53–1.35%), excellent solubility, and high glass transition temperature (308–450 °C). The PI derived from the new diamine and the very rigid naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA) was soluble in N‐methyl‐2‐pyrrolidone, chloroform, m‐cresol, and cyclohexanone. The unsymmetric di‐tert‐butyl pendent groups significantly enhance the rotational barrier of the polymer chains; thus these PIs had high T_gs. The ¹H NMR spectrum of the diamine 3 revealed that the protons of 4‐aminophenoxy moiety are not chemical shift equivalent. This is because the steric hindrance of the bulky di‐tert‐butyl groups prevents the benzene ring of 4‐aminophenoxy moiety from rotating freely. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2443–2452, 2009     

Augmented keyframe

In surveillance applications, keyframes are usually used to summarize important video contents. However, most traditional keyframe extraction approaches just select some video frames from the input video, while the information in these selected video frames are insufficient and cannot let the users perceive the events happened in the original video easily. In this paper, we propose a novel keyframe generating technique to condense the contents of a surveillance video clip captured by a static camera into a still picture (augmented keyframe). The augmented keyframe is a more meaningful keyframe augmented with representative objects, important contents (human faces, license plate, etc.), motion status (represented as icons) and some marks of the moving objects in a still picture. This new technique consists of two major phases: content extraction and content synthesis. Some testing results of the proposed augmented keyframe are also presented and compared with results obtained by the traditional keyframe approach.     

A novel self-coupled dual-mode ring resonator and its applications to bandpass filters

A novel dual-mode ring resonator with self-coupled segments, called a self-coupled ring resonator, is proposed. The self-coupling between ring segments provides the same mode perturbation effect as the conventional methods of adding stub, cutting notch, or varying line impedance on the ring resonator. The mode perturbation and transmission-zero generation due to the self-coupling effect are analyzed with the even-odd mode theory. The self-coupled ring resonator can have the capacitive or inductive perturbation simply by controlling the impedance ratio and coupling coefficients of self-coupled sections. For both perturbation cases, the transmission zeros exist at even multiples of the passband center frequency, resulting in wide stopband range. Also, only for the capacitive perturbation case, two transmission zeros are found on both sides of the passband, which brings a pseudo-elliptic bandpass response. In comparison with the regular uniform ring resonator, the self-coupled ring resonator takes shorter ring length, giving the compact size feature when applied to a bandpass filter design. A 2.45-GHz low-temperature co-fired ceramic bandpass filter based on the self-coupled ring resonator was designed to verify the proposed theory.     

New Meroditerpenoids from a Taiwanese Marine Sponge Strongylophora Durissima

In addition to strongylophorines 1 (3), 2 (4), 3 (5) and 8 (6), two new meroditerpenoids named strongylophorines 9(1) and 11 (2) were isolated from a Taiwanese marine sponge Strongylophora durissima. The structures of the new compounds were established by spectral methods and chemical derivatizations.     

Macrocyclic Polyether Phase Transfer Catalysts for Free Radical Polymerization of Acrolein

Macrocyclic polyethers, e.g., crown ethers and cryptands, were prepared and employed as phase transfer catalysts for free radical polymerization of acrolein, a vinyl monomer, with persulfates (S₂O₈^2–) as initiators. The catalytic abilities of various macrocyclic polyethers as catalysts for the free radical polymerization of acrolein were found to be in the order: benzo‐15‐crown‐5 > dibenzo‐18‐crown‐6 > 12‐crown‐4 > 15‐crown‐5 > 18‐crown‐6 > cryptand‐22 with sodium persulfate (Na₂S₂O₈) as initiator. Sodium persulfate proved to be a better initiator than ammonium persulfate or potassium persulfate with benzo‐15‐crown‐5 as a catalyst. Effects of solvents and temperature on the catalytic polymerization were also investigated. The polymerization rates in various solvents were in the order: dioxane > benzene > acetonitrile > acetone > dichloromethane > hexane > water. Comparison between bulk polymerization and solution polymerization was also made. Higher polymerization rate was observed at higher temperature. The molecular weights of polyacrolein and the conversion of monomer in reaction period were determined with gel permeation chromatography and ultra‐violet spectrophotometry, respectively. Concentration effects of crown ether and initiator were also investigated and discussed.     

Triphenylphosphine‐Mediated Reduction of Electron‐Deficient Propargyl Ethers to the Allylic Ethers

Semihydrogenation of α,β‐unsaturated ynoates and ‐ynones bearing a γ‐alkoxy group can be performed using triphenylphosphine and water. α,β‐Unsaturated ynoates were reduced to a mixture of cis and trans α,β‐unsaturated enoates, whereas, ynones were reduced to trans α,β‐unsaturated enones as the only products.     

A compact RCS formula for a dihedral corner reflector at arbitraryaspect angles

A compact closed-form formula for the RCS of a perfectly conducting right dihedral corner reflector at arbitrary aspect angles is presented. The approach is based on a combination of ray tracing, physical optics (PO), and the physical theory of diffraction (PTD). There is good agreement between the results obtained using the closed-form formula and those obtained by the shooting and bouncing rays (SBR) technique     

Compact microstrip dual-band bandpass filters design using genetic-algorithm techniques

An optimization scheme based on hybrid-coded genetic-algorithm (GA) techniques is presented to design compact dual-band bandpass filters with microstrip lines. A representation scheme is proposed to represent an arbitrary microstrip circuit as a set of data structures. Each data structure in the set describes a simple two-port network with the corresponding connection method and electrical parameters. The optimization algorithm based on conventional GAs is then applied to simultaneously search for the appropriate circuit topology and the corresponding electrical parameters with dual-band characteristic. Two examples are designed and implemented to validate the proposed algorithm. In the first example, the 3-dB fractional bandwidth of the low and high bands is 35% and 17%, respectively. It has return losses larger than 10 dB from 2.14 to 2.96 and 5.14 to 6.06 GHz. In the second example, the 3-dB fractional bandwidth of the low and high bands is 9.9% and 7.9%, respectively. The return losses are larger than 10 dB from 3.37 to 3.64 and 5.27 to 5.62 GHz. The sizes of the proposed filters are nearly half as small as those of the filters presented before. All the studies are completed on a computer with a 2.4-GHz microprocessor, and the computing time of two examples is 6 and 3 min, respectively.