The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei ^58Fe and ^208 pb at s=3fm, a length in which the effective surfaces of these nuclei are 3 fm apart. As a result of neu...The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei ^58Fe and ^208 pb at s=3fm, a length in which the effective surfaces of these nuclei are 3 fm apart. As a result of neutron flow, the N/Z value rapidly reaches an equilibrium distribution. Meanwhile the system, originally in the fusion valley, is injected into the asymmetric fission valley. The dynamic process of the composite nucleus in the asymmetric fission valley is treated with a two-parameter Smoluchowski equation. It is shown that the probability to overcome the asymmetric fission barrier and to achieve compound nucleus configuration, hence the fusion cross section is obviously suppressed due to the effect of isospin equilibrium.展开更多
The dynamical process in the superheavy nucleus synthesis is studied on the basis of the two-dimensional Smoluchowski equation. Special attention is paid to the isotope dependence of the cross section for the superhea...The dynamical process in the superheavy nucleus synthesis is studied on the basis of the two-dimensional Smoluchowski equation. Special attention is paid to the isotope dependence of the cross section for the superheavy nucleus formation by means of making a comparison among the reaction systems of ^54Re＋204pb, ^56Re ＋206Pb, and ^58Fe＋^208Pb. It is found by this comparison that the formation cross section is very sensitive to the conditional saddle-point height and the neutron separation energy of the compound nucleus. Reaction systems with lower height of conditional saddle-point and smaller neutron separation energy are more favourable for the synthesis of the superheavy nucleus.展开更多
The lifetimes of a decays of the recently produced isotopes of the elements 112, 114, 116 and the element ^294118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin appr...The lifetimes of a decays of the recently produced isotopes of the elements 112, 114, 116 and the element ^294118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin approximation. The a decay barriers have been determined in the quasimolecular shape path within a generalized liquid drop model including the proximity effects between nuclei in a neck, the mass and charge asymmetry and the precise nuclear radius. These calculations provide reasonable estimates for the observed a decay lifetimes. The calculated results have been compared with the results of the density-dependent M3Y effective interaction and the experimental data. It is indicated that the theoretical foundation of the generalized liquid drop model is as good as that of the microscopic DDM3Y model, at least in the sense of predicting the T1/2 values as long as one uses a correct a decay energy. The half lives of these new nuclei are well tested from the consistence of the macroscopic, the microscopic and the experimental data.展开更多
As part of a long time analysis to examine the ecological impacts of heavy rain coupled to soil degradation, soil fungal communities from two closely spaced sites bearing distinct ecology—one receiving heaviest rainf...As part of a long time analysis to examine the ecological impacts of heavy rain coupled to soil degradation, soil fungal communities from two closely spaced sites bearing distinct ecology—one receiving heaviest rainfall but degraded patch on earth and the other pristine sacred grove forest were investigated over a period of three years. Cherrapunji besides being highest rainfall receiving area, is characterized by complete deforestation and soil erosion with sparse grasses forming the surface growth, whereas the sacred forests are conserved in their pristine nature due to religious beliefs of the indigenous tribes. The effect of deforestation and land degradation on soil microbes, soil organic carbon, soil nitrate nitrogen, soil pH, soil temperature, and fungal CFU/g were investigated from the two contrasting sites. The sites showed great variability in physical and chemical parameters including soil composition, temperature, pH, soil carbon, nitrogen content, water availability and enzyme activities. The population count of fungi was higher in sacred forest soil than degraded land of Cherrapunji. In both soil types, Penicillium perpurogenum markedly dominated and the co-dominant species (Aspergillus sp., Fusarium sp. and Trichoderma sp.) were common in both virgin and degraded soils. A total of 63 species were identified during the study period. The species composition between the two sites showed some variation as Syncephalastrum sp., S. chartarum, Gliocladium sp., Eupenicillium osmophilum and Eurotium sp. were not present in Cherrapunji. The undisturbed sacred forest fungal communities had significantly higher Simpson, Shannon and evenness indices than that of degraded soil of Cherrapunji. The prolonged anthropogenic activity in the area leading to degradation coupled with heavy rainfall has decreased the diversity level of fungal communities and masked the pristine differentiating effect of soil on the fungal community.展开更多
If eternal return (永恒轮回说)is the heaviest of burdens,then our lives can stand out against it in all their splendid (辉煌的)lightness.But,is heaviness truly deplorable (凄惨的)and lightness splendid?The heaviest of...If eternal return (永恒轮回说)is the heaviest of burdens,then our lives can stand out against it in all their splendid (辉煌的)lightness.But,is heaviness truly deplorable (凄惨的)and lightness splendid?The heaviest of burdens crushes us.We sink beneath it.It pins us to the ground.The heaviest of burdens is,therefore,simultaneously (同时的)an image of life's most intense fulfillment. The heavier the burden,the closer our lives come to the earth;the more real and truthful they become.展开更多
基金Supported by the National Natural Science Foundation of China under Grants Nos 10235020 and 10235030, and the Major State Basic Research Development Programme under Grant No G200007400.
文摘The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei ^58Fe and ^208 pb at s=3fm, a length in which the effective surfaces of these nuclei are 3 fm apart. As a result of neutron flow, the N/Z value rapidly reaches an equilibrium distribution. Meanwhile the system, originally in the fusion valley, is injected into the asymmetric fission valley. The dynamic process of the composite nucleus in the asymmetric fission valley is treated with a two-parameter Smoluchowski equation. It is shown that the probability to overcome the asymmetric fission barrier and to achieve compound nucleus configuration, hence the fusion cross section is obviously suppressed due to the effect of isospin equilibrium.
基金Supported by the National Natural Science Foundation of China under Grants Nos 10235020 and 10235030, and the Major State Basic Research and Development Programme of China under Grant No G200007400.
文摘The dynamical process in the superheavy nucleus synthesis is studied on the basis of the two-dimensional Smoluchowski equation. Special attention is paid to the isotope dependence of the cross section for the superheavy nucleus formation by means of making a comparison among the reaction systems of ^54Re＋204pb, ^56Re ＋206Pb, and ^58Fe＋^208Pb. It is found by this comparison that the formation cross section is very sensitive to the conditional saddle-point height and the neutron separation energy of the compound nucleus. Reaction systems with lower height of conditional saddle-point and smaller neutron separation energy are more favourable for the synthesis of the superheavy nucleus.
基金Supported by the Major State Basic Research and Development Programme of China under Contract No G2000077400, the National Natural Science Foundation of China under Grant Nos 10505016, 10235020, 10235030, 10275094, 10075080 and 10575119, the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX2-SW-N02, National Key Programme for Basic Research of the Ministry of Science and Technology under Grant Nos 2001CCB01200 and 2002CCB00200, and the DFG of Germany.
文摘The lifetimes of a decays of the recently produced isotopes of the elements 112, 114, 116 and the element ^294118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin approximation. The a decay barriers have been determined in the quasimolecular shape path within a generalized liquid drop model including the proximity effects between nuclei in a neck, the mass and charge asymmetry and the precise nuclear radius. These calculations provide reasonable estimates for the observed a decay lifetimes. The calculated results have been compared with the results of the density-dependent M3Y effective interaction and the experimental data. It is indicated that the theoretical foundation of the generalized liquid drop model is as good as that of the microscopic DDM3Y model, at least in the sense of predicting the T1/2 values as long as one uses a correct a decay energy. The half lives of these new nuclei are well tested from the consistence of the macroscopic, the microscopic and the experimental data.
文摘As part of a long time analysis to examine the ecological impacts of heavy rain coupled to soil degradation, soil fungal communities from two closely spaced sites bearing distinct ecology—one receiving heaviest rainfall but degraded patch on earth and the other pristine sacred grove forest were investigated over a period of three years. Cherrapunji besides being highest rainfall receiving area, is characterized by complete deforestation and soil erosion with sparse grasses forming the surface growth, whereas the sacred forests are conserved in their pristine nature due to religious beliefs of the indigenous tribes. The effect of deforestation and land degradation on soil microbes, soil organic carbon, soil nitrate nitrogen, soil pH, soil temperature, and fungal CFU/g were investigated from the two contrasting sites. The sites showed great variability in physical and chemical parameters including soil composition, temperature, pH, soil carbon, nitrogen content, water availability and enzyme activities. The population count of fungi was higher in sacred forest soil than degraded land of Cherrapunji. In both soil types, Penicillium perpurogenum markedly dominated and the co-dominant species (Aspergillus sp., Fusarium sp. and Trichoderma sp.) were common in both virgin and degraded soils. A total of 63 species were identified during the study period. The species composition between the two sites showed some variation as Syncephalastrum sp., S. chartarum, Gliocladium sp., Eupenicillium osmophilum and Eurotium sp. were not present in Cherrapunji. The undisturbed sacred forest fungal communities had significantly higher Simpson, Shannon and evenness indices than that of degraded soil of Cherrapunji. The prolonged anthropogenic activity in the area leading to degradation coupled with heavy rainfall has decreased the diversity level of fungal communities and masked the pristine differentiating effect of soil on the fungal community.
文摘If eternal return (永恒轮回说)is the heaviest of burdens,then our lives can stand out against it in all their splendid (辉煌的)lightness.But,is heaviness truly deplorable (凄惨的)and lightness splendid?The heaviest of burdens crushes us.We sink beneath it.It pins us to the ground.The heaviest of burdens is,therefore,simultaneously (同时的)an image of life's most intense fulfillment. The heavier the burden,the closer our lives come to the earth;the more real and truthful they become.
