A radix-8 wafer scale FFT processor

Wafer Scale Integration promises radical improvements in the performance of digital signal processing systems. This paper describes the design of a radix-8 systolic (pipeline) fast Fourier transform processor for implementation with wafer scale integration. By the use of the radix-8 FFT butterfly wafer that is currently under development, continuous data rates of 160 MSPS are anticipated for FFTs of up to 4096 points with 16-bit fixed point data.     

Velocity, electromechanical coupling factor and acoustic loss of surface shear waves propagating along x-axis on rotated Y-cut plates of LiNbO3

Velocity and propagation loss of surface shear waves are measured on free-space and metallised surfaces of LiNbO3 crystals along the x-axis of rotated Y-cut plates as a function of rotation about the x-axis between 35° and 70°. The coupling factor obtained from the velocities is 0.20 for a 35° rotated Y-cut plate and 0.09 for a 70° plate. The coupling factor changes linearly with the rotation angle. The propagation losses over the whole range measured here are less than 5 dB/cm on both free-space and on metallised surfaces. These losses are fairly low and very favourable for fabricating s.a.w. filters.     

Resonant s.a.w. filter using surface shear wave mode on LiTaO3 substrate

A low-loss narrow band (below 3%) resonant filter has been achieved using twin-turn reflectors and a surface shear wave mode on 36° YX LiTaO3 substrate.     

Synthesis of a Sialic Acid Containing Complex‐Type N‐Glycan on a Solid Support

On solid ground : A new solid‐phase synthesis of N‐linked glycans featuring 1) highly stereoselective β‐mannosylation and microfluidic α‐sialylation and 2) efficient glycosylation of the N‐phenyltrifluoroacetimidate units on JandaJel resin is reported. Reagent concentration effects by a fluorous solvent are effectively applied, and the use of these methods results in the first synthesis of a sialic acid containing complex‐type N‐glycan on a solid support.

     

Structural scaffold of 18-crown-6 tetracarboxylic Acid for optical resolution of chiral amino acid: x-ray crystal analyses of complexes of D- and L-isomers of serine and glutamic acid

(+)-18-crown-6 tetracarboxylic acid (18C6H4) has been used as a chiral selector for D/L-amino acids in HPLC, where L-isomer is usually eluted prior to D-isomer, except for the case of serine. To clarify why serine exhibits the reverse order for the elusion, the chiral interactions of D- and L-serines with (+)-18C6H4 were investigated by the X-ray single crystal analyses, together with the case of D- and L-glutamic acids, which exhibit the usual elution order in HPLC. The backbone structures (amino, Calpha-H and carboxyl groups) of these four amino acids showed the nearly same interaction with (+)-18C6H4 despite their different chirality. In contrast, the hydroxyl group of L-serine side chain formed a hydrogen bond with the carboxyl group of (+)-18C6H4, whereas such a interaction was not formed for the side chain of D-serine and D- and L-glutamic acids. Thus, it was shown that the exception of D/L-serine from the first elution rule of L-isomer in HPLC is due to the presence and absence of a hydrogen bond formation of its side chain OH group.     

Pd-catalyzed benzylic C-h amidation with benzyl alcohols in water: a strategy to construct quinazolinones

A novel method for the synthesis of 4-phenylquinazolinones via a palladium-catalyzed domino reaction of o-aminobenzamides with benzyl alcohols is developed. This protocol involves N-benzylation, benzylic C-H amidation, and dehydrogenation in water, which may play an important role in the smooth generation of the (η(3)-benzyl)palladium species by activation of the hydroxyl group of the benzyl alcohol.     

Structural scaffold of 18-crown-6 tetracarboxylic acid for optical resolution of chiral amino acid: X-ray crystal analyses and energy calculations of complexes of D- and L-isomers of tyrosine, isoleucine, methionine and phenylglycine

To clarify the structural scaffold of (+)-18-crown-6 tetracarboxylic acid ((+)-18C6H4) for the optical resolution of a chiral amino acid, the crystal structures of its equimolar complexes with L- and D-isomers of tyrosine (Tyr), isoleucine (Ile), methionine (Met) and phenylglycine (PheG) were analysed by X-ray diffraction methods. (+)-18C6H4 took very similar conformations for all complexes. Although the chemical structure of (+)-18C6H4 is C2-symmetric, it took a similar asymmetric ring conformation of radius ca. 6.0 A. In all complexes, the amino group of chiral amino acids was located near the center of the ring and formed three hydrogen bonds and five electrostatic interactions with eight oxygen atoms of the ether ring and carboxyl groups. Also, the Calpha atom of chiral amino acids participated in Calpha-H...O interaction with the oxygen atom of (+)-18C6H4. In contrast, the carboxyl group of chiral amino acids did not directly interact with (+)-18C6H4. These results indicate that the structural scaffold of (+)-18C6H4 for the optical resolution of chiral amino acids is mainly based on the mode of interaction of (+)-18C6H4 with the amino and Calpha-H groups of chiral amino acids. The differences in interaction pattern and binding energy between the L- and D-isomers of each amino acid are discussed in relation to the chiral recognition of (+)-18C6H4.     

Numerical analysis of fatigue striations

A computational model was developed to numerically analyse fatigue striations. The inclined strip yield model with continuous distributions of infinitesimal dislocations was utilized to express the crack tip plasticity in this model. The fatigue crack tip blunting process was approximated by sequential activation of two slip lines under loading, and crack closure during unloading was taken into account. The plastic zone at a growing fatigue crack tip at the maximum load was independent of the crack growth up to ten cycles while the reversed plastic zone decreased in a size to one twentieth of that at the maximum load as the crack grew. The ratio of these plastic zone sizes and also the crack tip opening displacement were quite different from the simple prediction by J.R. Rice for a stationary crack. The computed striation spacings were compared with the observed ones and moderate agreement between them obtained.     

Palladium-catalyzed benzylation of unprotected anthranilic acids with benzyl alcohols in water

Palladium-catalyzed benzylation of unprotected anthranilic acids with benzyl alcohols in the presence of Pd(OAc)(2) (5 mol %) and sodium diphenylphosphinobenzene-3-sulfonate (TPPMS, 10 mol %) in water at 120 °C for 16 h gave only dibenzylated anthranilic acids in good yields. Water may play important roles for the smooth generation of the (η(3)-benzyl)palladium species by activation of the hydroxyl group of the benzyl alcohol.     

Palladium-catalyzed mono-N-allylation of unprotected amino acids with 1,1-dimethylallyl alcohol in water

Palladium-catalyzed N-allylation of unprotected amino acids with 1,1-dimethylallyl alcohol were carried out. The reaction in the presence of Pd(OAc)(2) (5 mol%), sodium diphenylphosphinobenzene-3-sulfonate (TPPMS, 10 mol%), and AcONa (2 equiv) in water at 120 °C for 16 h in a sealed tube gave only mono-N-allylated amino acids in good yield.