Photoinduced electron transfer and excitation energy transfer in directly linked zinc porphyrin/zinc phthalocyanine composite

Photoinduced electron transfer (ET) and excitation energy transfer (ENT) reactions in monomer and slipped-cofacial dimer systems of a directly linked Zn porphyrin (Por)-Zn phthalocyanine (Pc) heterodyad, ZnPc-ZnPor, were investigated by means of the picosecond and femtosecond transient absorption spectroscopies. In the dimer dyad system of two heterodyads connected through the coordination bond between two imidazolyl-substituted ZnPor bearing ZnPc, ZnPc-ZnPor(D), the rapid ENT from the ZnPor to ZnPc in the subpicosecond time region was followed by photoinduced charge separation (CS) and charge recombination (CR) with time constants of 47 and 510 ps, respectively. On the other hand in the monomer dyad system, no clear charge-separated state was observed although the CS with a time constant of 200 ps and CR with < or =70 ps were estimated. These results indicated that the dimer slipped-cofacial arrangement of pair porphyrins is advantageous for the effective production of the CS state. This advantage was discussed from the viewpoint of a decrease in the reorganization energy of the dimer relative to that of the monomer system. In addition, the electrochemical measurements indicated that the strong interaction between ZnPc and ZnPor moieties also contributed to the fast CS process despite the marginal driving force for the CS process. The dimer dyad of ZnPc-ZnPor provides full advantages in efficiencies of the light harvesting and the CS state production.     

Gain and noise figure improvements in a shorter wavelength region of EDFA using a macrobending approach

Gain and noise figure improvements are demonstrated in a shorter wavelength region of a double-pass EDFA using a macrobending approach. The EDF is wound in a small radius to suppress the amplified spontaneous emission at the longer wavelength in order to achieve a high amplification in the shorter wavelength. Gain enhancements of about 12–14 dB are obtained with macrobending at the wavelength region between 1480 and 1530 nm. The macrobending also reduces the noise figure of the EDFA at wavelengths shorter than 1525 nm with a maximum improvement of 25 dB.     

On polynomials with a prescribed zero

Let us denote byΛ _{n, 1} the supremum of (max_∥z∥=1∥p′ _n (z)∥)/ (max_∥z∥=1∥p _n (z)∥) taken over all polynomialsp _n of degree at mostn having a zero on the unit circle {z ∈ C∶∥z∥=1}. We show that Λn.1=n-(π ²/16)(1/n)+O(1/n ².     

Second order wave loads on large monolithic offshore structures

This paper considers the wave loads on large monolithic offshore structures. The second order wave force formulae developed by Rahman and Heaps, applicable to large circular cylinders in waves, are extended to evaluate the overturning moments on large circular cylinders. The theory is then applied to square section caissons in waves, to predict the wave loads on these structures. These calculations are performed using the exact form of the second order velocity potential, φ₂, with arbitrary wave number, k₂, and the approximate form of φ₂, with twice the value of the wave number of the first order velocity potential. The second order analytical predictions are compared with available experimental data for various ranges of wave parameters for both circular and square caissons in large amplitude waves.     

CuI-catalyzed Coupling Reactions of Aryl Iodides with Amides Using L-Proline and KF/Al2O3

An efficient experimentally simple and inexpensive catalyst system for the selective amidation of aryl iodides using 15 mol% of CuI as catalyst, 15 mol% of L-proline as ligand and KF/Al2O3 as a base in toluene is described.