Room temperature c.w. operation of InGaAsP/InP heterostructure lasers emitting at 1.56 ?m

Room-temperature c.w. operation of InGaAsP/InP heterostructure lasers grown by liquid-phase epitaxy was achieved at 1.56 ?m. An active InGaAsP layer was essentially sandwiched by InP, though a thin InGaAsP buffer layer was deposited to prevent the melt-back of the active layer. Threshold current was typically 300 mA for a 17 ?m wide oxide-defined stripe laser.     

Iron–Nitrogen‐Doped Vertically Aligned Carbon Nanotube Electrocatalyst for the Oxygen Reduction Reaction

A highly active iron–nitrogen‐doped carbon nanotube catalyst for the oxygen reduction reaction (ORR) is produced by employing vertically aligned carbon nanotubes (VA‐CNT) with a high specific surface area and iron(II) phthalocyanine (FePc) molecules. Pyrolyzing the composite easily transforms the adsorbed FePc molecules into a large number of iron coordinated nitrogen functionalized nanographene (Fe–N–C) structures, which serve as ORR active sites on the individual VA‐CNT surfaces. The catalyst exhibits a high ORR activity, with onset and half‐wave potentials of 0.97 and 0.79 V, respectively, versus reversible hydrogen electrode, a high selectivity of above 3.92 electron transfer number, and a high electrochemical durability, with a 17 mV negative shift of E _1/2 after 10 000 cycles in an oxygen‐saturated 0.5 m H₂SO₄ solution. The catalyst demonstrates one of the highest ORR performances in previously reported any‐nanotube‐based catalysts in acid media. The excellent ORR performance can be attributed to the formation of a greater number of catalytically active Fe–N–C centers and their dense immobilization on individual tubes, in addition to more efficient mass transport due to the mesoporous nature of the VA‐CNTs.     

Ultrafine grain formation in face centered cubic metals during severe plastic deformation

The evolution mechanisms of new high-angle boundaries as well as ultrafine grains at large strains were studied by means of multidirectional forging (MDF) of pure copper at low temperature and aluminum alloy at high temperature, where dynamic recovery operates as a main restoration process. The structural changes can be characterized by the evolution of deformation bands such as microshear or kink bands at moderate strains. Multidirectional forging accelerates the evolution of many mutually crossing microshear or kink bands developed in various directions. The misorientations between (sub)grains increased gradually with increasing cumulative strain, finally leading to the development of a new fine-grained structure. The dynamic grain formation can be resulted from in situ or continuous dynamic recrystallization which is discussed in detail.     

Effects of additives on prebreakdown phenomena in n-hexane

Prebreakdown phenomena in n-hexane are observed in detail for positive and negative polarities by using simultaneously a high speed schlieren technique and an LED current measuring system, when an impulse voltage (1.1/225 μs) is applied to a point-to-plane electrode gap. Furthermore, the effects of several additives on the streamer propagation are investigated. Especially the effects of electron-trapping additives on negative streamer propagation and of low ionization potential additives on the positive streamer propagation, are examined, as is a correlation between the shape and the propagation velocity of the streamers     

Fast and slow electrons in liquid Ar and N2 mixtures

Fast and slow electron current signals in N₂/Ar liquid mixtures have been observed. From the fast signal, the drift velocity and life time of delocalized electrons in the liquid with N₂ molar fractions X=N₂/(N₂+Ar) below 20 mol% were obtained for field strengths E between 5 and 45 kV/cm. The mobility for delocalized electrons in the liquids was shown to decrease exponentially with X as indicated in a previous paper. However, the mobility for localized electrons was shown to increase with increasing X, but only slightly around the N₂ liquid value     

Molecular recognition by wall-assembling-type nanocavity in aqueous media

Steroid cyclophanes, each having a macrocyclic ring attached to four bile acid moieties via chiral lysine connectors, were synthesized, and the binding of the 2-naphthylphenylketone (guest) to the steroid cyclophanes in water was investigated. The circular dichroism spectra of the steroid cyclophane with cholic acid and L-lysine were significantly affected by the binding of the guest, and the induced circular dichroism based on the absorption of the achiral guest was also observed. The binding of the guest to the steroid cyclophane with cholic acids and D-lysines induced changes in the circular dichroism spectra with the opposite sign of the molecular ellipticities. An induced circular dichroism spectral change was not observed upon binding of the guest to the analogous host without OH sites. These results strongly suggest that the guest is conformationally fixed through hydrogen bonding between the carbonyl group of the guest and the steroidal hydroxyl group of the host. The assembly of only four steroid residues on the macrocyclic ring probably provided a hydrophobic nanocavity for hydrogen bonding.     

Binding of organic anions by synthetic supramolecular metallopores with internal Mg2+-aspartate complexes

We report that cation-selective transmembrane pores formed by synthetic p-octiphenyl beta barrels with internal aspartate residues can be transformed into anion-permeable metallopores with internal Mg(2+)-aspartate complexes. These metallopores are shown to be useful for fluorimetric sensing of a broad variety of organic anions of biological relevance such as phytate, heparin, thiamine phosphates, and adenosine triphosphate. The negligible flippase activity measurable for Mg(2+)-free pores indicates that transmembrane p-octiphenyl beta barrels do not disturb the lipid bilayer suprastructure, in other words, they form barrel-stave rather than toroidal pores.