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The study of soil enzyme activities under different land use is of importance for exploration of the soil quality evolution and its evaluation during the revegetation at karst area in Nanchuan, Chongqing, China. Seven kinds of land use were chosen as subject, aiming at revealing the changes in soil enzyme activities through experimental and statistical analysis. The results showed that different land use significantly influenced the enzyme activities. Soil urease, invertase, catalase and amylase behaved the different change. A descending order of urease activity was artificial forest, natural forest, shrubbery, grassland, slope field into terrace, rock desertification and farmland. As to invertase and amylase, they have no clear change orderliness with land use change. Moreover, no significant change was observed in catalase activity and the lower value was found in natural forest. The above results cannot reflect the land use effect on the enzyme activities. According to the soil enzyme index (SEI), it can be seen that the SEI changed with an order of natural forest > artificial forest > grassland > shrubbery > farmland > slope field into terrace > rock desertification, which can objectively and fully evaluate the land use change in soil enzyme.

Preliminary results of a high resolution coherent vacuum ultraviolet study of photoion-pair formation in HF/DF are reported. These results include threshold ion-pair production (TIPPS) and total photoion-pair yield spectra, which show sharp resonances due to predissociating Rydberg states. Detailed analysis of the spectra provides precise energies for the ion-pair thresholds, and insight into the mechanism for ion-pair formation.

We present the first threshold ion-pair production spectrum of a triatomic molecule. We have recorded the ion-pair yield spectrum and TIPP spectrum for the H2S → H++SH- ion-pair channel using single-photon excitation. From the TIPP spectrum, we have determined the H−SH bond energy (31451 ± 4 cm-1) to unprecedented accuracy and demonstrated the formation of weakly bound H+−SH- (J‘) ion-pair states, with rotational excitation of the SH- anion up to J‘ = 4. The bound nature of these states, and the assigned spectrum that results from their field dissociation suggests that this technique can be applied to many other triatomic and larger polyatomic molecules in the future, leading to energetic, spectroscopic, and dynamical information about these species.

The protein product of the retinoblastoma (RB) gene is thought to function in a pathway that restricts cell proliferation. Recently, transforming proteins from three different classes of DNA tumor viruses have been shown to form complexes with the RB protein. Genetic studies suggest that these interactions with the RB protein are important steps in transformation by these viruses. In order to understand better the function of the RB-viral oncoprotein complexes, we have mapped the regions of the RB protein that are necessary for these associations. Two non-contiguous regions of RB were found to be essential for complex formation with adenovirus E1A or SV40 large T antigen. These two regions are found between amino acids 393 and 572 and 646 and 772. Interestingly, these binding sites on RB overlap with the positions of naturally occurring, inactivating mutations of the RB gene. These results strongly suggest that these viral oncoproteins are targeting a protein domain that is an important site in the normal function of the RB protein.