An Improved K-Means Algorithm Based on Initial Clustering Center Optimization

The K-means algorithm is widely known for its simplicity and fastness in text clustering.However,the selection of the initial clus?tering center with the traditional K-means algorithm is some random,and therefore,the fluctuations and instability of the clustering results are strongly affected by the initial clustering center.This paper proposed an algorithm to select the initial clustering center to eliminate the uncertainty of central point selection.The experiment results show that the improved K-means clustering algorithm is superior to the traditional algorithm.

Cluster Based Strategy to Improve Competitiveness of Rare Earth Industry in China——Taking Emerging Rare Earth Industry Cluster in Baotou As An Example

China′s rare earth industry has shown its strong competence, but notably this competence is mostly based on the comparative advantages in natural resources and production costs that will not provide a long-term momentum for the growth of the industrial competitiveness. It has become an urgent task now for China′s rare earth industry to improve its competitiveness through adjusting the product structure and enhancing the technological application, to gain much healthier and more sustainable growth in the future. This paper aims to present a new development strategy based on the industry cluster theory to improve the competitiveness of China′s rare earth industry with a case study on the emerging rare earth industry cluster in Baotou. The paper first reviews the cluster theory and explains why it matters to industrial competitiveness briefly, and then proposes a general framework for implementing cluster policies and strategies in practice. Following that, a case to study the emerging rare earth industry cluster in Baotou was presented and a cluster initiative based on the general framework was developed. The objectives of the cluster initiative and the role of government on initiative organizing and cluster upgrading were discussed in detail. In the end, general implications drawn from the case of Baotou were summarized, which try to provide some insights for applying cluster-based strategies to the rare earth industry of China.

Essential role of the iron-sulfur cluster binding domain of the primase regulatory subunit Pri2 in DNA replication initiation

DNA primase catalyzes de novo synthesis of a short RNA primer that is further extended by replicative DNA polymerases during initiation of DNA replication. The eukaryotic primase is a heterodimeric enzyme comprising a catalytic subunit Pril and a regulatory subunit Pri2. Pri2 is responsible for facilitating optimal RNA primer synthesis by Pril and mediating interaction between Pril and DNA polymerase o for transition from RNA synthesis to DNA elongation. All eukaryotic Pri2 proteins contain a conserved C-terminal iron-sulfur （Fe-S） cluster-binding domain that is critical for primase catalytic activity in vitro. Here we show that mutations at conserved cysteine ligands for the Pri2 Fe-S cluster markedly decrease the protein stability, thereby causing S phase arrest at the restrictive temperature. Furthermore, Pri2 cysteine mutants are defective in loading of the entire DNA pol α-primase complex onto early replication origins resulting in defective initiation. Importantly, assembly of the Fe-S cluster in Pri2 is impaired not only by mutations at the conserved cysteine ligands but also by increased oxidative stress in the sodlA mutant lacking the Cu/Zn superoxide dismutase. Together these findings highlight the critical role of Pri2＇s Fe-S cluster domain in replication initiation in vivo and suggest a molecular basis for how DNA replication can be influenced by changes in cellular redox state.