InGaAsP multiple quantum well edge-emitting light-emitting diode showing low coherence characteristics using selective-area metalorganic vapor phase epitaxy

Low coherence multiple-quantum well edge-emitting light-emitting diodes were obtained using selective-area metalorganic vapor-phase epitaxial growth, which utilized growth rate enhancement on an open stripe region between mask stripes. An optical absorption region, which was controlled by selective-area growth, was introduced to suppress optical feedback. At a driving current of 100 mA and an ambient temperature of 25°C, a power of 55 μW was coupled into a single-mode fiber, and a broad spectrum without spectral ripple was observed. Low coherence characteristics and very small temperature dependence were obtained in the temperature range from -40°C to 85°C. The modulation bandwidth was 210 MHz at a bias current of 100 mA.     

Dynamics of FLCs with a tilted bookshelf structure using time-resolved FTIR spectroscopy

Time-resolved FTIR spectroscopy with microsecond resolution was applied to the switching process of FLCs using an IR polarizer attached to a microscope whose axis was set along the aligning direction (direction of SiO flux). A tilted bookshelf geometry with a layer tilt angle of approximately 34° was obtained by alignment using obliquely evaporated SiO layers in a CaF₂ cell with about 1.7 μm gap. Six kinds of FLC mixtures were prepared by mixing 5 wt % of a chiral molecule with host mixtures of phenylpyrimidines. By monitoring an absorption band at 1432 cm^-1, assigned to vibrational modes of the pyrimidine skeleton, it was found that the molecular long axis either rotates along the upper side or along the lower side of the cone during switching. Moreover, we investigated the relationship between the rotational direction of the directors and the stability of the dark level transmission during multiplexing. The dark level transmission during rotation along the upper side of the cone may fluctuate less than that during rotation along the lower side of the cone. We found that the bias stability of the dark level transmission is closely related to the direction of the rotation along the cone. The direction of the rotation of FLCs along the cone was therefore found to play an important role in realizing high contrast ratios during multiplexing.     

FOURIER TRANSFORM INFRARED SPECTRAL STUDIES ON THE SCHIFF BASE MODE OF ALL-trans BACTERIORHODOPSIN and ITS PHOTOINTERMEDIATES,K and L*

Abstract– Difference Fourier transform infrared spectra were recorded for bacteriorhodopsin upon irradiation at 230, 170 or 77 K, which gave, respectively, the spectrum of the M, L or K intermediate minus unphotolyzed all-trans bacteriorhodopsin (denoted as BR). By replacement of the Schiff base nitrogen with ¹⁵N, or of either its hydrogen at N or C₁₅ with deuterium, the vibrational bands related to the Schiff base were identified and the isotope-shifts evaluated for BR, K and L. The 1348 cm^?l band of BR and K and the 1400 cm^?1 band of L were sensitive to each of these isotope substitutions. The 1254 cm^?1 band of BR, the 1245 cm^?1 band of K and the 1301 cm^?1 band of L were sensitive to either N- or C₁₅-deuteration but not to ¹⁵N-substitution. The N—D in-plane bending vibration of K and L appeared at 969 and 997 cm^?1, respectively, upon substitution with D₂O. All the results show that L is larger in frequencies related to the N—H in-plane bending vibration than K or BR and suggest that L has the strongest interaction with the protein. Among the bands containing an N—H bending vibration, the 1348 cm^?1 band of K was more intense than the corresponding band of L at 1400 cm^?1. The C₁₅-deuteration-induced upshift of the 1245 cm^?1 band of K was unobservable for the 1301 cm^?1 band of L. Such differences between L and K might be brought about by a distortion in the retinal moiety close to the protonated Schiff base of the 13-cis chromophore.     

Atmospheric pressure waves in the field of volcanology

Atmospheric pressure waves are a notable phenomenon associated with explosive volcanic eruptions. They can provide us with information about eruption processes that are useful both scientifically and practically. In this paper, we give a brief review of studies that have been carried out on this phenomenon in the field of volcanology. Then, we introduce a prototype tool called ‘MOVE’ (Mobile Observatory for Volcanic Explosions). It is a remote-controlled vehicle carrying various instruments to observe pressure waves and the eruption processes. PACS 91.40.Dr · 91.40.Ft · 93.65.+e · 93.85.+qThis paper was based on work presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan on March 1–3, 2005.     

Delayed nonlinear cournot and bertrand dynamics with product differentiation

Dynamic duopolies will be examined with product differentiation and isoelastic price functions. We will first prove that under realistic conditions the equilibrium is always locally asymptotically stable. The stability can however be lost if the firms use delayed information in forming their best responses. Stability conditions are derived in special cases, and simulation results illustrate the complexity of the dynamism of the systems. Both price and quantity adjusting models are discussed.     

Possible Involvement of a Tetrahydrobiopterin in Photoreception for UV‐B‐induced Anthocyanin Synthesis in Carrot

Our previous studies of action spectra for UV‐B‐induced anthocyanin accumulation in cultured carrot cells indicated that a reduced form of pterin, possibly tetrahydrobiopterin, contributes to UV‐B photoreception. In this report, we provide additional evidence for the involvement of pterin in UV‐B light sensing. UV‐B‐induced phenylalanine ammonia‐lyase (PAL) activity was considerably suppressed by N‐acetylserotonin (an inhibitor of tetrahydrobiopterin biosynthesis), and this suppression was partially recovered by adding biopterin or tetrahydrobiobiopterin. In addition, protein(s) specifically bound to biopterin were detected by radiolabeling experiments in N‐acetylserotonin‐treated cells. Furthermore, diphenyleneiodonium, a potent inhibitor of electron transfer, completely suppressed UV‐B‐induced PAL activity. These results suggest the occurrence of an unidentified UV‐B photoreceptor (other than UVR8, the tryptophan‐based UV‐B sensor originally identified in Arabidopsis) with reduced pterin in carrot cells. After reexamining published action spectra, we suggest that anthocyanin synthesis is coordinately regulated by these two UV‐B sensors.     

Pd-catalyzed cycloisomerization-allylation of 4-alkynones: synthesis of 5-homoallylfuran derivatives

In the presence of Pd₂(dba)₃-tBu₃P catalyst and Cs₂CO₃, cycloisomerization-allylation reactions of 4-alkynone derivatives with allyl carbonates in MeCN proceed in 5-exo mode to give highly-substituted furans having homoallyl groups at 5-position.     

PIFA-mediated oxidative cycloisomerization of 2-propargyl-1,3-dicarbonyl compounds: divergent synthesis of furfuryl alcohols and furfurals

PhI(OCOCF₃)₂ (PIFA) in the presence of trifluoroacetic acid (TFA) in CH₂Cl₂ efficiently promotes the oxidative cycloisomerization of 2-propargyl 1,3-dicarbonyl compounds to give 4,5-disubstituted furfuryl alcohols. PIFA in hexafluoroisopropanol (HFIP) or PIFA-BF₃·OEt₂ in CH₂Cl₂ bring about the direct formation of furfurals from 2-propargyl 1,3-dicarbonyl compounds. In a few cases, PhIO is suitable for the direct formation of furfurals.     

Cage-shaped borate esters with tris(2-oxyphenyl)methane or -silane system frameworks bearing multiple tuning factors: geometric and substituent effects on their Lewis acid properties

Boron complexes that contain new tridentate ligands, tris(o‐oxyaryl)methanes and ‐silanes, were prepared. These complexes had a cage‐shaped structure around a boron center and showed higher Lewis acidity and catalytic activity than open‐shaped boron compounds. The cage‐shaped ligands determined the properties of the borates by altering the geometry and were consistently bound to the metal center by chelation. The synthesized compounds were L?B(OC₆H₄)₃CH, L?B(OC₆H₄)₃SiMe, and its derivatives (L=THF or pyridine as an external ligand). Theoretical calculations suggested that the cage‐shaped borates had a large dihedral angle (C_ipso‐O‐B‐O) compared with open‐shaped borates. The geometric effect due to the dihedral angle means that compared with open‐shaped, the cage‐shaped borates have a greater Lewis acidity. The introduction of electron‐withdrawing groups on the aryl moieties in the cage‐shaped framework increased the Lewis acidity. Substitution of a bridgehead Si for a bridgehead C decreased the Lewis acidity of the boron complexes because the large silicon atom reduces the dihedral angle of C_ipso‐O‐B‐O. The ligand‐exchange rates of the para‐fluoro‐substituted compound B(OC₆H₃F)₃CH and the ortho‐phenyl‐substituted compound B(OC₆H₃Ph)₃CH were less than that of the unsubstituted borate B(OC₆H₄)₃CH. The ligand‐exchange rate of B(OC₆H₄)₃SiMe was much faster than that of B(OC₆H₄)₃CH. A hetero Diels–Alder reaction and Mukaiyama‐type aldol reactions were more effectively catalyzed by cage‐shaped borates than by the open‐shaped borate B(OPh)₃ or by the strong Lewis acid BF₃?OEt₂. The cage‐shaped borates with the bulky substituents at the ortho‐positions selectively catalyzed the reaction with less sterically hindered substrates, while the unsubstituted borate showed no selectivity.     

Redox-controlled, reversible rearrangement of a tris(2-pyridylthio)methyl ligand on nickel to an isomer with an “N,S-confused” 2-pyridylthiolate arm

Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(μ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained.