Two-stage photo-biological production of hydrogen by marine green alga Platymonas subcordiformis

A marine green alga, Platymonas subcordiformis, was demonstrated to photobiologically evolve hydrogen (H-2) after the first stage of photosynthesis, when subjected to a two-phase incubation protocol in a second stage of H2 production: anaerobic incubation in the dark followed by the exposure to light illumination. The anaerobic incubation induced hydrogenase activity to catalyse H? evolution in the following phase of light illumination. H,) evolution strongly depended upon the duration of anaerobic incubation, deprivation of sulphur (S) from the medium and the medium pH. An optimal anaerobic incubation period of 32 h gave the maximum H2 evolution in the second phase in the absence of sulphur. Evolution of H,) was greatly enhanced by 13 times when S was deprived from the medium. This result suggests that S plays a critical role in the mediation of H-2 evolution from R subcordiformis. A 14-fold increase in H-2 production was obtained when the medium pH increased from 5 to 8; with a sharp decline at pH above eight. H-2 evolution was enhanced by 30-50% when supplementing the optimal concentrations of 25 mM acetate and 37.5 mM glucose. (C) 2003 Elsevier B.V. All rights reserved.

The effects of CO2 addition on the partial oxidation of heptane for hydrogen generation

The effects of CO2 on the partial oxidation of heptane for hydrogen generation have been studied. Based on the experimental results and thermodynamic equilibrium calculations, the validity of CO2 addition to weaken the hot spots, and the feasibility of the autothermal operation are discussed.

Theoretical study on analytical potential function and spectroscopic parameters for CaF molecule

The equilibrium properties and potential energy curves of the ground electronic state of CaF have been calculated using the Brueckner Doubles calculation with a triples contribution added [BD(T)] and the gradient-corrected density functional theory with three-parameter exact exchange mixing (B3LY-P) method, with 6-311 + G*,6-311 + G(2df,2pd) and 6-311 + G(3df,3pd) basis sets. All the computational PECs are fitted to analytical potential energy functions using Murrell-Sorbie, Huxley and Tang-Toennies potentials. Based on this, the spectroscopic parameters are calculated, and then compared with some other theoretical and experimental data. (C) 2004 Elsevier B.V. All rights reserved.

Theoretical study of the femtosecond-resolved photoelectron spectrum of the NO molecule

The effect of laser fields on the NO interaction potentials is obtained by the calculation of time-resolved photoelectron spectrum (TRPES) using the time-dependent wave-packet method. The calculation not only shows that the overlap of the pump-probe pulses makes some NO molecular "invisible" states visible, but also that the coupling strength and the positions of relevant curves change on increasing the laser intensity. These changed potentials affect their dynamical behavior and influence the shape and position of each peak in TRPES. That the coupling strength of relevant potentials can be changed by the field-matter interaction is consistent with our ab initio calculations.

Characterization of the acid sites in dealuminated nanosized HZSM-5 zeolite with the probe molecule trimethylphosphine

The acid sites in dealuminated HZSM-5 zeolite with crystal sizes down to the nanoscale were firstly characterized by the probe molecule trimethylphosphine (TMP). As evidenced by the combination of P-31 CP/MAS NMR, Al-27 MAS and H-1 --> Al-27 CP/MAS NMR measurements, the Bronsted acid sites of both microsized and nanosized HZSM-5 could be decreased upon the dealumination of zeolitic framework after hydrothermal treatment. At the same time, the appearance of Lewis acid sites was observed. The dealuminated nanosized HZSM-5 is easier to form Lewis acid sites than microsized HZSM-5, and the type of Lewis acid sites in nanosized HSM-5 is more than one. In addition, the origin of Lewis acid sites is mainly associated with the aluminum at ca. 30 ppm, in the Al-27 MAS NMR spectra, and only a part of which in the dealuminated HZSM-5 zeolite acts as Lewis acid sites. (C) 2002 Elsevier Science B.V. All rights reserved.