alpha-decay half-lives and Q(alpha) values of superheavy nuclei

The alpha-decay half-lives of recently synthesized superheavy nuclei (SHN) are investigated by employing a unified fission model (UFM) where a new method to calculate the assault frequency of alpha emission is used. The excellent agreement with the experimental data indicates the UFM is a useful tool to investigate these alpha decays. It is found that the alpha-decay half-lives become more and more insensitive to the Q(alpha) values as the atomic number increases on the whole, which is favorable for us to predict the half-lives of SHN. In addition, a formula is proposed to compute the Q(alpha) values for the nuclei with Z >= 92 and N >= 140 with a good accuracy, according to which the long-lived SHN should be neutron rich. Several weeks ago, two isotopes of a new element with atomic number Z = 117 were synthesized and their alpha-decay chains have been observed. The Q(alpha) formula is found to work well for these nuclei, confirming its predictive power. The experimental half-lives are well reproduced by employing the UFM with the experimental Q(alpha) values. This fact that the experimental half-lives are compatible with experimental Q(alpha) values supports the synthesis of a new element 117 and the experimental measurements to a certain extent.

Computational study on the addition of HCN to methanimine catalyzed by formamidine and formamide

In this paper, we have carried out a theoretical study on the addition of HCN to methanimine with formamidine or formamide using second-order Moller-Plesset perturbation (MP2) method with 6-31 + G(d,p) basis sets. At MP2 level. a high-energy, intermediate has been located for each pathway. The addition of HCN to methanimine with formamidine has the lowest free energy barrier according to the calculations at MP2 level. (C) 2004 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.

Concise synthesis of novel practical sulfamide-amine alcohols for the enantioselective addition of diethylzinc to aldehydes

Novel sulfamide-amine alcohol ligands were designed using a grafting strategy and synthesized from readily available starting materials via a simple, efficient method. The key features of these ligands for the asymmetric addition of diethylzinc to aldehydes included stability, enhanced effectiveness without using Ti((OPr)-Pr-i)(4), suitability for a variety of aldehydes, the ability to operate at room temperature, and selectability to afford either absolute configuration products with enantiomeric excess up to >99%.

Highly enantioselective conjugate addition of diethylzinc to acyclic enones with fine-tunable phosphite-pyridine ligands

A new series of fine-tunable phosphite-pyridine (P,N) ligands derived from (S)-2-amino-T-hydroxy-6,6'-dimethyl-1,1'-biphenyl and (S)-2-amino-2'-hydroxy-4,4',6,6'-tetramethyl-1,1'-biphenyl was employed in Cu(I)-catalyzed conjugate addition of diethylzinc to acyclic enones. Excellent enantioselectivities (up to 98% ee) and highly catalytic activities were achieved for a variety of acyclic enones.

Structural probing of D-fructose derived ligands for asymmetric addition of diethylzinc to aldehydes

A series of new chiral ligands derived from D-fructose have been synthesized and applied in the enantioselective addition of diethylzinc to aldehydes. Comparison of the enantioselectivities obtained with these ligands demonstrated that the catalytic properties are highly dependent upon the structure of ligands, a rational explanation of the structural effects on the catalytic properties is provided. (C) 2003 Elsevier Science Ltd. All rights reserved.

Effect of addition of Zn on the catalytic activity of a Co/HZSM-5 catalyst for the SCR of NOx with CH4

The selective catalytic reduction (SCR) of NOx by methane in the presence of excess oxygen was studied on a Zn-Co/HZSM-5 catalyst. It was found that the addition of Zn could improve effectively the selectivity of methane towards NOx reduction. When prepared by a coimpregnation method, the Zn-Co/HZSM-5 catalyst showed much higher catalytic activity than the two catalysts of a Zn/Co/HZSM-5 and Co/Zn/HZSM-5 prepared by the successive impregnation method. It is considered that there exists a cooperative effect among the Zn, Co and zeolite, which enhances the reduction of NO to NO2 reaction and the activation of methane. (C) 2002 Elsevier Science B.V. All rights reserved.

A systematic approach to standard addition methods in instrumental analysis

Nine cases of standard addition methods in instrumental analysis, including linear instruments, a non-linear response, the electrochemical Nernst equation, and radiochemical techniques.