Nitride‐based hetero‐field‐effect‐transistor‐type photosensors with extremely high photosensitivity

AlGaN/GaN hetero‐field‐effect‐transistor‐type (HFET‐type) photosensors are fabricated with a p‐GaInN optical gate for the detection of visible light. These photosensors employ a two‐dimensional electron gas at the heterointerface between AlGaN and GaN as a highly conductive channel with a high electron mobility. By changing the InN molar fraction in the p‐GaInN optical gate, the wavelength range of the photosensitivity of the HFET‐type photosensors can be controlled. The photosensitivity of the AlGaN/GaN HFET‐type photosensors with a p‐GaInN optical gate greatly surpassed those of commercially available Si pin and Si avalanche photodiodes, and was comparable to those of photomultiplier tubes. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Molecular design of "super" hydrogelators: understanding the gelation process of azobenzene-based sugar derivatives in water

[structure: see text]. 1: R = beta-D-glucopyranoside. 2: R = alpha-D-glucopyranoside. 3: R = alpha-D-galactopyranoside. 4: R = alpha-D-mannopyranoside. As an attempt to rationally design aqueous organogelators, a bolaamphiphilic azobenzene derivative (1) bearing two sugar groups was synthesized. Compound 1 formed a gel in water even at concentrations as low as 0.05 wt % (0.65 mM). Spectroscopic studies and electron-micrographic observations have clarified the gel structure and the origin of the gelation ability for water.     

Schizophyllans carrying oligosaccharide appendages as potential candidates for cell-targeted antisense carrier

Schizophyllans carrying beta-lactoside and alpha-mannoside appendages were prepared from native schizophyllan through NaIO4 oxidation followed by reductive amination using aminoethyl-beta-lactoside and alpha-mannoside, respectively. The resulting schizophyllans form stable macromolecular complexes with polynucleotides, such as poly(C) and poly(dA). Specific affinity between these macromolecular complexes and saccharide-binding proteins was demonstrated by surface plasmon resonance and agarose gel staining assays. beta-lactoside-appended schizophyllan enhanced an antisense activity in hepatocytes which express lactoside-binding proteins on their cell surfaces.     

Rhodium-catalyzed asymmetric 1,6-addition of aryltitanates to enynones giving axially chiral allenes

[reaction: see text] The addition of aryltitanate reagents ArTi(OPr-i)4Li to 3-alkynyl-2-en-1-ones in the presence of chlorotrimethylsilane and a rhodium-(R)-segphos as a catalyst proceeded in a 1,6-fashion to give a high yield of axially chiral allenylalkenyl silyl enol ethers with up to 93% ee.     

Direct time-domain observation of ultrafast dephasing in adsorbate-substrate vibration under the influence of a hot electron bath: Cs adatoms on Pt(111)

The stretching vibration of Cs adsorbed on Pt(111) is excited coherently by resonant stimulated Raman excitation and its time evolution is probed by fs time-resolved second harmonic generation as a function of pump laser fluence I. As I increases, a fast dephasing component with the lifetime of tau=0.7 ps grows, being superimposed on a slow one with tau=1.9 ps. The fast component is a manifestation of pure dephasing caused by elastic and inelastic scattering of hot electrons at adsorbate.     

Direct preparation of allylic zirconium reagents from zirconocene-olefin complexes and alkenes

A novel method for preparation of allylic zirconium reagents directly from 1-alkenes via zirconocene-olefin complex has been developed. Selective transfer of the hydride of zirconocene allyl hydride complex, a tautomer of zirconocene-olefin complex, to diisopropyl ketone generates the corresponding zirconocene alkoxide allyl. The allylic zirconium reagents formed effects stereoselective allylation of aldehyde at 25 degrees C and -78 degrees C to provide syn- and anti-homoallyl alcohols, respectively. The anti-isomer is formed via a six-membered chair transition state under kinetic control. The syn-selectivity can be rationalized by considering isomerization of the anti-adduct by a retroallylation process.     

On the 4D effective theory in warped compactifications with fluxes and branes

We present a systematic way to derive the four-dimensional effective theories for warped compactifications with fluxes and branes in the ten-dimensional type IIB supergravity. The ten-dimensional equations of motion are solved using the gradient expansion method and the effective four-dimensional equations of motions are derived by imposing the consistency condition that the total derivative terms with respect to the six-dimensional internal coordinates vanish when integrated over the internal manifold. By solving the effective four-dimensional equations, we can find the gravitational backreaction to the warped geometry due to the dynamics of moduli fields, branes and fluxes.     

Lanthanoid element recognition on surface-imprinted polymers containing dioleylphosphoric acid as a functional host.

Surface-imprinted polymers have been newly developed for the separation of lanthanoid elements: i.e. La(III), Ce(III), and Dy(III). The imprinted polymers were prepared by surface template polymerization with dioleylphosphoric acid, which exhibits a high affinity to lanthanoids, as a functional host molecule. Separation behavior of La(III), Ce(III) and Dy(III) was investigated with the imprinted polymers, and the imprinting effect of the polymers was evaluated in comparison with that of the unimprinted polymers and also with a conventional solvent extraction method for the same lanthanoid ions. The results indicate that the increase of selectivity for Dy(III) compared to the rest of the ions by the surface-imprinted polymers originated from a synergistic effect of both the affinity with the functional host molecule in nature and the size exclusion by the cavity formed on the polymer surface.     

Are Bessel Beams Supportable in Graded-Index Media?

We disprove the existence of a family of Bessel beams [J. Durnin, J.J. Miceli, Jr. and J.H. Eberly: Phys. Rev. Lett. 58 (1987) 1499] for any realistic graded-index media.