Synthesis of a novel host molecule of cross-linking-polymeric-beta-cyclodextrin-o-vanillin furfuralhydrazone and spectrofluorimetric analysis of its identifying cadmium

A novel host inclusion complex of cross-linking-polymeric-beta-cyclodextrin-o-vanillin furfuralhydrazone (beta-CDP-OVFH) was synthesized and characterized with IR and 1H NMR spectra to confirm its structure. The coordination reaction of the host reagent with Cd(2+) was studied and the optimum reacting conditions were observed carefully. A highly selective and sensitive spectrofluorimetric determination of trace amount of cadmium was proposed based on the reaction of Cd(2+) with beta-CDP-OVFH in ammonia water-ammonium acetate buffer medium of pH = 11.0. The molar ratio of beta-CDP-OVFH to Cd(2+) was 1:1. The maximum excitation and emission wavelengths were 393 and 494 nm, respectively. The linear range of this method was from 3.0 to 500 microg l(-1) with a detection limit of 0.80 microg l(-1). The effect of interferences in the determination of cadmium was investigated and the results showed that the host reagent had quite high capacity of identifying Cd(2+). The proposed method was successfully applied to the determination of trace amount of Cd(2+) in mussel and tea samples.     

A novel approach to the synthesis of 6-amino-7-hydroxy-flavone

A novel approach to the synthesis of 6-amino-7-hydroxyflavone (1) is described. Reaction in acetone of 2',4'-dihydroxy-5'-nitroacetophenone and benzoyl chloride in the presence of potassium carbonate affords 3-benzoyl-7-hydroxy-6-nitroflavone, which is cleaved in 5% ethanolic potassium hydroxide to give 1-(2,4-dihydroxy-5-nitrophenyl)-3- phenyl-1,3-propanedione. The 1,3-diketone thus formed is then transformed into 7-hydroxy- 6-nitroflavone, followed by reduction to afford the title compound.     

Small peptides catalyze highly enantioselective direct aldol reactions of aldehydes with hydroxyacetone: unprecedented regiocontrol in aqueous media

[reaction: see text] L-Proline-based small peptides have been developed as efficient catalysts for the asymmetric direct aldol reactions of hydroxyacetone with aldehydes. Chiral 1,4-diols 7, which are disfavored products in similar aldol reactions catalyzed by either aldolases or L-proline, were obtained in high yields and enantioselectivities of up to 96% ee with peptides 3 and 4 in aqueous media.     

Parallelizing of macro-scale pseudo-particle modeling for particle-fluid systems

Particle methods such as SPH (smoothed particlehydrodynamics)[1,2], DEM (distinct-element model)[3],DPD (dissipative particle dynamics)[4— and pseudo- 6]particle modeling (PPM)[7,8] are getting more and morepopular as numerical methods in material science andfluid dynamics, due to their flexibility in simulatingcomplicated phenomena like fluid-solid coupling,multi-phase flow and large deformation and rupture insolid materials. However, a comm…     

Absence of charge inversion on rodlike polyelectrolytes with excess divalent counterions

Filamentous viruses such as fd and M13 are highly charged rodlike polyelectrolytes. In this study, we employ fd virus to test the recent prediction of charge inversion [Nguyen, Rouzina, and Shklovskii, J. Chem. Phys. 112, 2562 (2000)]. Light scattering measurements show bundle formation and resolubilization of fd viruses when MgCl(2) was added from 0 to 600 mM. The effective charge of fd was studied by measuring their electrophoretic mobility using a filament tracking method uniquely suited for the system. Monte Carlo simulations were performed under canonical ensemble to predict the charge distribution around the rodlike virus. Charge inversion, which has been suggested theoretically to accompany with bundle resolubilization, was not observed in either experiments or simulations. A modified analysis of force balance is called upon to account for these new findings.     

Diode-pumped passively mode-locked Nd:GdVO<Subscript>4</Subscript> laser with a GaAs saturable absorber mirror

We report on a diode end-pumped passively mode-locked Nd:GdVO₄ laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO₄ laser using a GaAs wafer as the saturable absorber. PACS 42.55.Rz; 42.60.Fc; 42.55.Xi.     

Preparation of CdO nanoparticles by mechanochemical reaction

CdO nanoparticles of 43 nm in crystal size were successfully synthesized by the mechanochemical reaction (CdCl₂ + Na₂CO₃) with NaCl as a diluent and subsequent thermal treatment at 700°C for 2 h. The samples were characterized by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Effect of calcination temperature on the crystal size of CdO nanoparticles was primarily investigated. The apparent activation energy of CdO nanoparticle formation during thermal treatment was calculated to be 12.2 kJ/mol.