Spectral Narrowing of a Varactor-Integrated Resonant-Tunneling-Diode Terahertz Oscillator by Phase-Locked Loop

Spectral narrowing of a resonant-tunneling-diode (RTD) terahertz oscillator, which is useful for various applications of terahertz frequency range, such as an accurate gas spectroscopy, a frequency reference in various communication systems, etc., was achieved with a phase-locked loop system. The oscillator is composed of an RTD, a slot antenna, and a varactor diode for electrical frequency tuning. The output of the RTD oscillating at 610 GHz was down-converted to 400 MHz by a heterodyne detection. The phase noise was transformed to amplitude noise by a balanced mixer and fed back into the varactor diode. The loop filter for a stable operation is discussed. The spectral linewidth of 18.6 MHz in free-running operation was reduced to less than 1 Hz by the feedback.     

Towards Tuneable Retaining Glycosidase‐Inhibiting Peptides by Mimicry of a Plant Flavonol Warhead

Retaining glycosidases are an important class of enzymes involved in glycan degradation. To study better the role of specific enzymes in deglycosylation processes, and thereby the importance of particular glycosylation patterns, a set of potent inhibitors, each specific to a particular glycosidase, would be an invaluable toolkit. Towards this goal, we detail here a more in‐depth study of a prototypical macrocyclic peptide inhibitor of the model retaining glycosidase human pancreatic α‐amylase (HPA). Notably, incorporation of l ‐DOPA into this peptide affords an inhibitor of HPA with potency that is tenfold higher (K_i=480 pm ) than that of the previously found consensus sequence. This represents a first successful step in converting a recently discovered natural‐product‐derived motif, already specific for the catalytic side‐chain arrangement conserved in the active sites of retaining glycosidases, into a tuneable retaining glycosidase inhibition warhead.     

Influence of Oxygen Ion Conduction on Nitric Oxide Decomposition

Ba₂In₂O₅, Ba₂Y₄O₉, and BaLa₂O₄ having brownmillerite-related structures were synthesized. Ionic conductivity and catalytic activity following the reduction of NO to N₂ were also investigated, both of which increased at the order-disorder transition temperature for oxygen vacancies of these compounds. It was made clear that the catalytic activity of NO decomposition reaction increased with a decrease in the order–disorder transition temperature. Moreover, it was found that ionic conductivity contributed to the catalytic activity of NO reduction to N₂.     

Fiber Formation in Medium and Ultra‐High‐Molecular‐Weight Polyhydroxybutyrate Blends under Shear Flow

Summary: Polyhydroxybutyrate (PHB) is an ideal bioplastic, however, this polymer undergoes a severe embrittlement process because of its spherulitic structure, rendering the material brittle. Using a series of in‐situ rheo techniques, we have previously observed only the rapid initial stage of shish formation, we term a partial shish, which existed at high shears in medium‐molecular‐weight PHB, = 360 000. The shish kebab morphology is anticipated to remove or severely lessen this embrittlement process whilst providing new properties and applications. For medium and ultra high‐molecular‐weight (MMWT, = 360 000/UHMWT, = 5 × 10⁶) PHB 99/1 and 99.5/0.5 blends only a partial shish is identified. However, the initial shish formation stage and subsequent stages were observed at 98/2 and 97/3 blend ratios resulting in a complete shish, we term the full shish, and fiber formation was evident. We believe this fiber morphology achieved by high molecular weights is crucial to sustaining the shish kebab structure for an excessive period.

Left: In‐situ rheo‐light scattering micrograph; 97/3 MMWT/UHMWT PHB at 100 s^?1 for 1 s shear shish held at 75 s. Right: In situ rheo‐optical micrograph; PHB fiber morphology observed at 50 s^?1 for 2 s shear 98/2 MMWT/UHMWT PHB after 1 min.     

Catalysis by Molten Metals and Molten Alloys

Abstract

It appears pertinent for the opening of this review to cite the work of Ipatiew [1]. In 1901 he reported that certain metals catalyzed the decomposition of alcohols even above the melting points of the catalyst metals, However, he gave no special attention to the catalytic activity of the molten metal (liquid metal), and thus 20 years or more elapsed without any significant advances in the research on the catalysis of the liquid metal.     

Charge transporting block copolymer for morphological control in light emitting device based on polymer blends

Bipolar charge transporting block copolymer composing of carbazole and oxadiazole monomers as hole and electron transporting units, respectively, was synthesized by nitroxide mediated radical polymerization. It is found that the current efficiency significantly increased with the addition of the block copolymer in the device based on polymer blend system. AFM measurement revealed that a phase-separated structure in the polymer blend layer changed to suitable morphology in the presence of block copolymer.     

Optimizing the dimensions of magnesium ammonium phosphate to maximize its ammonia uptake ability

Magnesium ammonium phosphate (MgNH₄PO₄·6H₂O:MAP) releases approximately 70% of its ammonia at a mild temperature of 378 K. The resultant material (magnesium hydrogen phosphate (MgHPO₄:MHP)-like material), which appears to be an amorphous phase, to remove ammonia from wastewater was investigated. Because the original size of MAP crystals was found to critically affect the kinetics of ammonia uptake by the corresponding MHP-like material, MAP with different sizes were synthesized by changing concentration, pH and temperature of the synthesis solution. The variation in the synthesis concentration was found to change the size of MAP as well as the aspect ratio of the long-axis to the short-axis. The rate of ammonia uptake depends primarily on the dimension of the short-axis of the corresponding MAP crystals. Furthermore, analysis of ammonia uptake using a method similar to the shrinking-core model shows approximately 0.5 μm from the surface is effectively used for ammonia uptake over a period of a realistic process time. Thus, the results suggest it is crucial to synthesize small MAP crystals with the size of short-axis less than 1 μm. Our results also show that small MAP crystals can be used at least four times repeatedly for ammonia uptake.     

The rapid,living, anionic polymerization of 2‐vinylnaphthalene at ambient temperature: Characterization of an n‐butyllithium/tetrahydrofuran system in 1,2,3,4‐tetrahydronaphthalene

We report the first well‐controlled room temperature anionic polymerization of 2‐vinylnaphthalene (2‐VNP), using alkyllithium (RLi) initiators. The nucleophilicity and solubility of the RLi as well as that of the 2‐vinylnaphthalenyllithium (VNPLi) and poly(2‐vinylnaphthalenyl)lithium (PVNPLi) propagating species were found to be very important factors in this reaction. An initiator system composed of n‐butyllithium (n‐BuLi) with tetrahydrofuran (THF) in 1,2,3,4‐tetrahydronaphthalene (THN) was determined to be the most effective of the various systems examined. The n‐BuLi/THF complex initiates polymerization and the resulting VNPLi/THF and PVNPLi/THF complexes act as propagating species at room temperature. These species offer adequate nucleophilicity and stability without promoting side reactions. As a result, rapid anionic polymerization was achieved. Various poly(2‐VNP) products with well‐defined polymeric chain structures were synthesized by this process at room temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41901.