Computational thermodynamics and microstructure simulations to understand the role of grain boundary phase in Nd-Fe-B hard magnets

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High-power microwave generation by double-anode virtual cathode oscillator

The virtual cathode oscillator (vircator) is one of the promising devices to oscillate high-power microwaves. Simplicity and high-power capability are advantages. However, the low efficiency and frequency stability are serious problems. In this article, we dealt double anode to strengthen the microwave interactions. The measurement result shows that the output of the virtual cathode oscillator can be progress by using the double-anode.     

HPLC/PDA determination of carminic acid and 4-aminocarminic acid using relative molar sensitivities with respect to caffeine

To accurately determine carminic acid (CA) and its derivative 4-aminocarminic acid (4-ACA), a novel, high-performance liquid chromatography with photodiode array detector (HPLC/PDA) method using relative molar sensitivity (RMS) was developed. The method requires no analytical standards of CA and 4-ACA; instead it uses the RMS values with respect to caffeine (CAF), which is used as an internal standard. An off-line combination of ¹H-quantitative nuclear magnetic resonance spectroscopy (¹H-qNMR) and HPLC/PDA was able to precisely determine the RMSs of CA^274nm/CAF^274nm and 4-ACA^274nm/CAF^274nm. To confirm the performance of the HPLC/PDA method using RMSs, the CA and 4-ACA contents in test samples were tested using four different HPLC-PDA instruments and one HPLC-UV. The relative standard deviations of the results obtained from five chromatographs and two columns were less than 2.7% for CA^274nm/CAF^274nm and 1.1% for 4-ACA^274nm/CAF^274nm. The ¹H-qNMR method was directly employed to analyse the CA and 4-ACA contents in test samples. The differences between the quantitative values obtained from both methods were less than 5% for CA and 3% for 4-ACA. These results demonstrate that the HPLC/PDA method using RMSs to CAF is a simple and reliable quantification method that does not require CA and 4-ACA certified reference materials.     

Electrochromic materials using mechanically interlocked molecules

Recent investigations on the design and synthesis of electrochromic materials based on switchable three-station [2]catenanes are summarized. The reasoning and preliminary experiments behind the design of electrochemically controllable red–green–blue (RGB), donor–acceptor [2]catenanes are presented. A basis for color generation is discussed in which the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), serves as the π-electron deficient ring which circumrotates between three π-electron rich recognition sites within a macrocyclic polyether, generating the three different colors (RGB) based on the different charge transfer interactions between the tetracationic cyclophane and recognition sites based on 1,5-dioxynaphthalene (R), tetrathiafulvalene (G) and benzidine (B). Issues relating to the realization of an RGB [2]catenane are raised and discussed: they include (i) color tuning, (ii) thermodynamic considerations, (iii) electrochemistry on model compounds, (iv) molecular design, (v) the electrochemical behavior of three-station [2]catenanes and (vi) electrochromism in polymer gel matrices. Finally, the challenges that need to be met in the future if the ideal RGB catenane is to be prepared, are outlined.     

Correlation between Cu (I)-complexes and filling of via cross sections by copper electrodeposition

In the manufacture of metal interconnects for semiconductor devices, trenches and vias in dielectric layers on the Si wafer are filled by copper electrodeposition. The acceleration of deposition at the bottom of trenches and vias is a key to the bottom-up filling of these high aspect ratio cavities. We report the detection of this acceleration effect by rotating ring disk electrode experiments. The Cu (I)-complex, which forms on the disk electrode, was captured as a current (I_ring) on the ring electrode. I_ring increased in periodic reverse pulse current mode, as compared to direct or pulse current. The periodic reverse pulse current produced the most bottom-up filling based on microscopic observations of via cross sections. I_ring increased with the additions of Cl⁻, which also produced greater bottom-up filling. I_ring increased with additions of SPS, which were also found to improve bottom-up filling.     

Role of the backbone conformation at position 7 in the structure and activity of marinostatin, an ester-linked serine protease inhibitor

Rational design of inhibitors: The cis-amide backbone at position 7 in the serine protease inhibitor marinostatin was replaced with an E or Z olefin. The E olefin analogue was not active, but the Z analogue was. The cis conformation might play a critical role in organizing a canonical structure for binding to proteases.     

Biomolecule-recognition gating membrane using biomolecular cross-linking and polymer phase transition

We present for the first time a biomolecule-recognition gating system that responds to small signals of biomolecules by the cooperation of biorecognition cross-linking and polymer phase transition in nanosized pores. The biomolecule-recognition gating membrane immobilizes the stimuli-responsive polymer, including the biomolecule-recognition receptor, onto the pore surface of a porous membrane. The pore state (open/closed) of this gating membrane depends on the formation of specific biorecognition cross-linking in the pores: a specific biomolecule having multibinding sites can be recognized by several receptors and acts as the cross-linker of the grafted polymer, whereas a nonspecific molecule cannot. The pore state can be distinguished by a volume phase transition of the grafted polymer. In the present study, the principle of the proposed system is demonstrated using poly(N-isopropylacrylamide) as the stimuli-responsive polymer and avidin-biotin as a multibindable biomolecule-specific receptor. As a result of the selective response to the specific biomolecule, a clear permeability change of an order of magnitude was achieved. The principle is versatile and can be applied to many combinations of multibindable analyte-specific receptors, including antibody-antigen and lectin-sugar analogues. The new gating system can find wide application in the bioanalytical field and aid the design of novel biodevices.     

Low methanol crossover and high performance of DMFCs achieved with a pore-filling polymer electrolyte membrane

We compared the performance of the membrane electrode assembly for direct methanol fuel cells (DMFCs) composed of a pore-filling polymer electrolyte membrane (PF membrane) with that composed of a commercial Nafion-117 membrane. In DMFC tests, the methanol crossover flux was 23% lower in the PF membrane than in the Nafion-117 membrane even though the thickness of the PF membrane was 43% that of Nafion-117. This led to a higher DMFC performance and the lower overpotential of the cathode of the PF membrane. Feeding an aqueous 10 M methanol solution at 50 °C produced a low cathode overpotential, as low as 0.40 V at 0.2 A in the PF membrane, whereas the potential was 0.65 V at 0.2 A in the Nafion-117 membrane. In contrast, the ohmic loss and anode overpotential were almost the same in the two membranes. We confirmed that a reduction in methanol crossover using the PF membrane results in lower cathode overpotential and higher DMFC performance. In addition, the electro-osmotic coefficient was estimated as 1.3 in the PF membrane and 2.6 in Nafion-117, based on a water mass-balance model and values showing that the PF membrane prevents the flooding of the cathode at a low gas flow rate using. A highly concentrated methanol solution can be applied as a fuel without decreasing DMFC performance using PF membranes.     

Development of a Peristaltic Crawling Robot Using Planar Link Mechanisms

The field of bio‐mechanisms, which develops new machines that use motion and control of organisms as a model, is attracting attention. We examined the peristaltic crawling of an earthworm as a transport function in place of wheels or ambulation, and have developed a robot running inside a tube. In this robot, a joint corresponding to the earthworm's segment is driven by a DC motor. This paper presents the experimental result of the peristaltic crawling of an actual earthworm and the evaluation result of the transport mechanism of a prototype robot. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.