Based on our structural model and a tight-binding Hamiltonian the eIectronic structure has been calculated by use of a recursion method (RM) for two models of the tetragonal DO22 and the cubic Ll2 crystal structures i...Based on our structural model and a tight-binding Hamiltonian the eIectronic structure has been calculated by use of a recursion method (RM) for two models of the tetragonal DO22 and the cubic Ll2 crystal structures in Al3Ti+Cr for contrast, from which bonding characteristics have been discussed. The results for the interaction energy (IE) show that Cr prefers to replacing Al site. Cr partly replacing Al can change the IE between the atoms and make the constriction of lattice constant c and the elongation of lattice constant a for the DO22 and thereby may induce the change of crystal structure from DO22 to L12. The results for bond order integral (BOI) and IE between the atoms also show that the strong (110) directional Cr-Ti bondings are existed.Thus, Al3Ti-base intermetallic compounds with addition of the Cr atom still remain brittle.展开更多
The stability of the coordination compounds of the first transition series metal ions(Mn(Ⅱ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)and Zn(Ⅱ))with 2-mercaptopyridine-1- oxide is reported.A coordination compound CoL_2 is synthesized and...The stability of the coordination compounds of the first transition series metal ions(Mn(Ⅱ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)and Zn(Ⅱ))with 2-mercaptopyridine-1- oxide is reported.A coordination compound CoL_2 is synthesized and characterized for the first time.展开更多
A regional profile of AChE activity was noted in the Indian termite queen Odontotermes redemanni with the head recording the higher and body the lower range of activity. The enzyme characteristics such as substrate an...A regional profile of AChE activity was noted in the Indian termite queen Odontotermes redemanni with the head recording the higher and body the lower range of activity. The enzyme characteristics such as substrate and temperature optima were more or less similar while pH requirement for optimum AChE activity varied from 7.0 to 7.6 In vitro inhibition of head and body AChE was studied using pure and commercial anticholinesterase compounds. Interestingly, the commercial formulations like Metacid-50 and Carbaryl are potent enough at 1×10^(-8) M to produce 50% in vitro inhibition of AChE of head and body regions within 15 min of preincubation. A 20 min of preincubation (t0.5) was necessary to record 50% in vitro inhibition of AChE with known and pure anticholinesterase compounds such as DFP (3.5×10^(-10)M) and physostigmine (3.6 ×10^(-10)M). It is surmised that (a) the response of the head and body AChE to the commercial formulations of the insecticides may be used as a reliable and sensitive bioindicator of pesticidal contamination of the terrestrial environment and (b) termite control may be successfully done with the application of organophosphate or carbamate compounds.展开更多
文摘Based on our structural model and a tight-binding Hamiltonian the eIectronic structure has been calculated by use of a recursion method (RM) for two models of the tetragonal DO22 and the cubic Ll2 crystal structures in Al3Ti+Cr for contrast, from which bonding characteristics have been discussed. The results for the interaction energy (IE) show that Cr prefers to replacing Al site. Cr partly replacing Al can change the IE between the atoms and make the constriction of lattice constant c and the elongation of lattice constant a for the DO22 and thereby may induce the change of crystal structure from DO22 to L12. The results for bond order integral (BOI) and IE between the atoms also show that the strong (110) directional Cr-Ti bondings are existed.Thus, Al3Ti-base intermetallic compounds with addition of the Cr atom still remain brittle.
文摘The stability of the coordination compounds of the first transition series metal ions(Mn(Ⅱ),Co(Ⅱ),Ni(Ⅱ),Cu(Ⅱ)and Zn(Ⅱ))with 2-mercaptopyridine-1- oxide is reported.A coordination compound CoL_2 is synthesized and characterized for the first time.
文摘A regional profile of AChE activity was noted in the Indian termite queen Odontotermes redemanni with the head recording the higher and body the lower range of activity. The enzyme characteristics such as substrate and temperature optima were more or less similar while pH requirement for optimum AChE activity varied from 7.0 to 7.6 In vitro inhibition of head and body AChE was studied using pure and commercial anticholinesterase compounds. Interestingly, the commercial formulations like Metacid-50 and Carbaryl are potent enough at 1×10^(-8) M to produce 50% in vitro inhibition of AChE of head and body regions within 15 min of preincubation. A 20 min of preincubation (t0.5) was necessary to record 50% in vitro inhibition of AChE with known and pure anticholinesterase compounds such as DFP (3.5×10^(-10)M) and physostigmine (3.6 ×10^(-10)M). It is surmised that (a) the response of the head and body AChE to the commercial formulations of the insecticides may be used as a reliable and sensitive bioindicator of pesticidal contamination of the terrestrial environment and (b) termite control may be successfully done with the application of organophosphate or carbamate compounds.
