An efficient copper-catalyzed coupling reaction of pyridin-2-ones with aryl and heterocyclic halides based on Buchwald's protocol

An efficient copper-catalyzed coupling reaction based on the Buchwald's protocol has been established for pyridin-2-ones with aryl iodides, aryl bromides, and heterocyclic bromides.     

Xenon Adsorption and Xe-129 NMR on Faujasite Zeolites

Faujasites of Si/Al = 2–5 were obtained by direct synthesis and (NH₄)SiF₆ dealumination. The dependence of their Xe-129 NMR and xenon adsorption isotherm on Al content was used to monitor the inhomogeneous distribution of Al in synthesized samples of faujasite.     

Soft X-ray yield measurement in a small plasma focus operated inneon

The United Nations University/International Center for Theoretical Physics Plasma Focus Facility (UNU/ICTP PFF), a small plasma focus, has proven very useful as a training device for research initiation and as a test bed for applications. In this work, its performance in terms of a soft X-ray (SXR) source is examined. The total SXR yield when operated in neon is measured using low-cost detectors, including a calorimeter and a five-channel filtered PIN system. For a charging voltage of 14 kV with 2.9 kJ stored energy, the optimum operating pressure in neon is found to be in the range of 2.7-3.3 torr, resulting in a total SXR yield of 6J/shot into 4π steradians measured by the calorimeter in agreement with the PIN detectors. Spectral data shows that 64% of the total SXR yield is contributed by the Ly-α and He-α lines and 36% by the rest, mainly the radiative recombination. The low total SXR yield (0.2 % of stored energy) is consistent with numerical computations of focus dynamics, which reveals that 3% of stored energy is converted into plasma energy. This low conversion rate into plasma energy is due to the large inductance of 110 nH of this simple single-capacitor device. Thus, for development as a SXR source, reduction of inductance is necessary     

Synthesis and properties of poly(1-phenyl-1-octyne)s containing stereogenic and chromophoric pendant groups

Poly(1-phenyl-1-octyne)s containing different stereogenic and chromophoric pendants {-[(C6H13)C=C(C6H4-p-CO2-R)]n-R=[(1S)-endo]-(-)-borneyl (P3), (1R,2S,5R)-(-)-menthyl (P4),―C6H4-p-(1R,2S,5R)-(-)-menthyl (P5), 2-napthyl (P6), 4-biphenylyl (P7)} have been designed and synthesized. The polymers are prepared in moderate yields by WCl6-Ph4Sn and possess high molecular weights (Mw up to 64000). The structures and properties of the polymers are characterized and evaluated by NMR, TGA, UV, CD, PL, and EL analyses...     

Photoluminescence and electroluminescence of a novel green-yellow emitting material-5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile

A new compound with intramolecular charge transfer (ICT) property—5,6-Bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile(BNPPDC) was synthesized. The new compound was strongly fluorescent in non-polar and moderately polar solvents, as well as in thin solid film. The absorption and emission maxima shifted to longer wavelength with increasing solvent polarity. The fluorescence quantum yield also increased with increasing solvent polarity from non-polar to moderately polar solvents, then decreased with further increase of solvent polarity. This indicates both “positive” and “negative” solvatokinetic effects co-existed. Using this material as hole-transporting emitter and host emitter, we fabricated two electroluminescent (EL) devices with structures of A (ITO/BNPPDC (45 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm) and B (ITO/N,N′-diphenyl-N,N′-bis-(3-methylphenyl) (1,1′-diphenyl)4,4′-diamine (TPD) (50 nm)/BNPPDC (20 nm)/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBI) (45 nm)/Mg:Ag (200 nm). The devices showed green-yellow EL emission with good efficiency and high brightness. For example, the device A exhibited a high brightness of 17400 cd/m² at a driving voltage of 11 V and a very low turn-on voltage (2.9 V), as well as a maximum luminous efficiency 3.61 cd/A. The device B showed a similar performance with a high brightness of 12650 cd/m² at a driving voltage of 13 V and a maximum luminous efficiency 3.62 cd/A. In addition, the EL devices using BNPPDC as a host and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as a dopant (configuration: ITO/TPD (60 nm)/BNPPDC:DCJTB (2%) (30 nm)/TPBI (35 nm)/Mg:Ag (200 nm)) showed a good performance with a brightness of 150 cd/m² at 4.5 V, a maximum brightness of 12600 cd/m² at 11.5 V, and a maximum luminous efficiency of 3.30 cd/A.     

Defect-mode dependence of two-photon-absorption enhancement in a one-dimensional photonic bandgap structure

A one-dimensional photonic crystal containing a single CdS defect layer of various thicknesses was fabricated. The dependence of the two-photon-absorption (TPA) coefficient on the defect mode was investigated by use of a femtosecond pump-probe method. Experimental results show that the TPA coefficient of the CdS defect layer depends strongly on the defect mode in the photonic bandgap. This is consistent with the predicted dependence of light intensity within the defect layer.     

Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.     

Iodine stabilization of a diode laser in the optical communication band

The iodine molecule has frequently been used as a frequency reference from the green to the near-infrared wavelength region (500-900 nm). We describe the frequency locking of the second-harmonic signal of a 197.2-THz (1520.25-nm) distributed-feedback diode laser to the absorption lines of the iodine hyperfine structure; a frequency jitter below 0.1 MHz was achieved at a 300-ms time constant. This scheme provides a simple, compact, and high-performance frequency reference in the optical communication band.     

Optical computations of cosine transforms

Utilizing the symmetrical properties of cosine transform, a coherent optical Fourier transform system has been modified to compute cosine transforms optically. The modification involves creating a symmetrical pattern at the input. Cosine transform is known to be useful for data compression and image coding especially when the image space-bandwidth product is finite. It is also attractive even when the image size becomes large but is not statistically stationary; in such case it should be processed in (M × M) stationary blocks of finite size.     

A critical comparison of projection microradiography and the 2X method

Summary It is shown that Cosslett's criticism on the 2X method is based partly on a misconception of the resolving power of the photographic film and partly on a fundamentally wrong comparison between projection and 2X method. A generally valid comparison is given for the cases where the resolving power is not limited by Fresnel diffraction. Finally it is shown that Fresnel fringes are smaller in the 2X method than in a comparable projection system.The authors wish to express their gratitude to Dr. J.Bouman for the discussions which contributed especially to § 2.