Mouse Mammary Tumor Virus Carrying a Bacterial supFGene Has Wild-Type Pathogenicity and Enables Rapid Isolation of Proviral Integration Sites

Mouse mammary tumor virus (MMTV) has frequently been used as an insertional mutagen to identify provirally activated mammary proto-oncogenes. To expedite and facilitate the process of cloning MMTV insertion sites, we have introduced a bacterial supF suppressor tRNA gene into the long terminal repeat (LTR) of MMTV, thus allowing selection of clones containing it in lambda vectors bearing amber mutations. The presence of supF in the LTR should circumvent the screening process for proviral insertion sites, since only those lambda clones with supF-containing proviral-cellular junction fragments should be able to form plaques on a lawn of wild-type Escherichia coli (i.e., lacking supF). The resulting virus (MMTVsupF) induced mammary tumors at the expected rate in infected mice, deleted the appropriate T-cell population by virtue of its superantigen gene, and stably retained the supF gene after passage via the milk to female offspring. To test the selective function of the system, size-selected DNA containing two proviral-cellular junction fragments from an MMTV supF-induced mammary tumor was ligated into λgtWES.λB, packaged, and plated on a supF-deficient bacterial host for selection of supF-containing clones. All plaques tested contained the desired cloned fragments, thus demonstrating the utility of this modified provirus for the rapid cloning of MMTV insertion sites

Evaluation on the Effect of Car Use Restriction Measures in Beijing

Recent years, with the rapid growth of car ownership in Beijing, urban transportation service level, air quality and energy consumption are facing great challenge. However, it is difficult to implement the measure of car use restriction because of all kinds of reasons. By taking chance of the 29th Olympic Games, Beijing municipal authority implemented the temporary measure of car use based on odd and even-numbered license plate. Then, after the 29th Olympic Games, Beijing municipal authority issued the measure of drive one day less a week on October, 11th 2008 to continue restricting car use. We collected transportation data about road travel speed, public transport operation, air quality and residents’ response from Oct. 2007 to Feb. 2009 period to evaluate the implementation effect of these car use restriction measures. The evaluation results show that these car use restriction measures have achieved fairly good effects on improving urban transportation and air quality. But the effects of current car use restriction measure are being counteracted by continually rapid growth of car ownership and use. Based on the analysis of the developing trend of Beijing transportation, we propose some recommendations for future integrated car use restriction measures in Beijing

Arc Characteristics and Welding Process of Laser K-TIG Hybrid Welding

The Q235 steel plate butt joint was successfully welded by the laser K-TIG hybrid welding method. The effects of hybrid welding process parameters such as welding current, the distance between heat sources, laser power, laser defocusing amount, and welding speed on the coupled arc profile and welding process stability were studied. The results indicated that the laser deflects the K-TIG arc, and the deflection angle becomes smaller as the arc current increases. After K-TIG generates small holes, if the laser beam acts on the bottom of the keyhole, the welded depth can be further increased; however, the laser power has little effect on the welded depth. The distance between heat sources is the main factor affecting the state of laser-arc coupling. Optical microstructures of welded joints showed that the grains in the arc zone were coarser than those in the laser zone, and there are more columnar crystals in the fusion zone. The microhardness of the weld center is significantly higher than that of the base metal, up to 220 HV. At the same time, the change of tensile strength of the weld under the influence of a single parameter was analyzed, and it was found that tensile properties of the weld first increased and then decreased with the increase of K-TIG arc current I, heat source distance D, and welding speed V, respectively. With the increase of laser power P, it first decreased and then increased, and with the increase of laser defocusing amount δf, it showed a downward trend

Solidification/stabilization of Pb-contaminated soil by using low-carbon binder derived from dehydrated waste concrete powders and GGBS

The low reactivity and high stability of waste concrete powder (WCP) hinder the promotion of recycled binder applications with WCP addition. This study provides an innovative utilization strategy for thermal-modified WCP (TMWCP) recycling as an environmentally friendly solidification/stabilization (S/S) binder material for Pb-contaminated soil by adding ground granulated blast furnace slag (GGBS). The S/S treated soils underwent performance evaluations including unconfined compressive strength and leaching tests. Furthermore, the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry tests were conducted to elucidate the underlying mechanisms. The results show that at an optimal heat treatment temperature of 600 °C for WCP, the S/S treated soil achieved a compressive strength of 4.2 MPa after 28 d of curing. Additionally, the optimum mixture ratio of TMWCP and GGBS was 9:1. It was found that the novel binder was much superior to OPC in terms of Pb immobilization and carbon emission reduction. When the dosage of the formed binder is twice that of OPC, it can compensate for the lack of strength in S/S treated Pb-contaminated soil

Simultaneously improved capacity and initial coulombic efficiency of Li-rich cathode Li[Li0.2Mn0.54Co0.13Ni0.13]O2 by enlarging crystal cell from a nanoplate precursor

Li-rich manganese layered oxide is one of the most promising cathode materials that meet the requirements for high-energy-density Li-ion batteries. However, a large irreversible capacity loss at the first cycle makes it difficult to be an applicable cathode material. Although wide investigations have been carried out to overcome such defect, researchers are still beset by the problems of how to concurrently improve the multiple performances of the cathode. In this work, Li[Li0.2Mn0.54Co0.13Ni0.13]O2 is synthesized, which delivers both improved high-energy capacity of 308 mAh g-1 and enhanced initial coulombic efficiency of 85%. The corresponding values of a contrast sample are only 245 mAh g-1 and 77%, respectively. Based on the data of bond distances, crystal cell parameters, and the calculated electron cloud density revealed by Rietveld analysis, an enlarged crystal cell mechanism is proposed. The improved performances are originated from the enlarged crystal cell, which facilitates the Li+ delithiation/lithiation from the octahedral and tetrahedral sites, accordingly increasing the discharge capacity and initial coulombic efficiency. The proposed method offers a strategy to simultaneously increase the initial coulombic efficiency and the specific capacity for Li ion batteries.Peer reviewed: YesNRC publication: Ye

Simultaneously improved capacity and initial coulombic efficiency of Li-rich cathode Li[Li0.2Mn0.54Co0.13Ni0.13]O2 by enlarging crystal cell from a nanoplate precursor

Li-rich manganese layered oxide is one of the most promising cathode materials that meet the requirements for high-energy-density Li-ion batteries. However, a large irreversible capacity loss at the first cycle makes it difficult to be an applicable cathode material. Although wide investigations have been carried out to overcome such defect, researchers are still beset by the problems of how to concurrently improve the multiple performances of the cathode. In this work, Li[Li0.2Mn0.54Co0.13Ni0.13]O2 is synthesized, which delivers both improved high-energy capacity of 308 mAh g-1 and enhanced initial coulombic efficiency of 85%. The corresponding values of a contrast sample are only 245 mAh g-1 and 77%, respectively. Based on the data of bond distances, crystal cell parameters, and the calculated electron cloud density revealed by Rietveld analysis, an enlarged crystal cell mechanism is proposed. The improved performances are originated from the enlarged crystal cell, which facilitates the Li+ delithiation/lithiation from the octahedral and tetrahedral sites, accordingly increasing the discharge capacity and initial coulombic efficiency. The proposed method offers a strategy to simultaneously increase the initial coulombic efficiency and the specific capacity for Li ion batteries.Peer reviewed: YesNRC publication: Ye

Site Selection Considerations of Spent Nuclear Fuel Reprocessing Plant in China

AbstractWith conversion of nuclear development strategy from “proper development” to “positive development” in China, the future nuclear power scale and the amount of the spent nuclear fuels will be enormous, the construction of spent nuclear fuel reprocessing plant will be necessary to meet the sustainable development requirement. Because of the huge investment and high environmental sensitivity, the site selection of spent nuclear fuel reprocessing plant has always been the focus of controversy. This article summarizes the site selection considerations from the technical feasibility, safety reliability, environmental compatibility and economic rationality for further discussion about the scientific site selection of spent nuclear fuel reprocessing plant in China