Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Contemporary Proton Therapy Systems Adequately Protect Patients from Exposure to Stray Radiation

Proton beam therapy has provided safe and effective treatments for a variety of adult cancers. In recent years, there has been increasing interest in utilizing proton therapy for pediatric cancers because it allows better sparing of healthy tissues. Minimizing exposures of normal tissues is especially important in children because they are highly susceptible to consequential late effects, including the development of a radiogenic second cancer, which may occur years or even decades after treatment of the first cancer. While the dosimetric advantage of therapeutic proton beams is well understood, relatively little attention has been paid to the whole-body exposure to stray neutron radiation that is inherent in proton therapy. In this report, we review the physical processes that lead to neutron exposures, discuss the potential for mitigating these exposures using advanced proton beam delivery systems, and present a comparative analysis of predicted second cancer incidence following various external beam therapies. In addition, we discuss uncertainties in the relative biological effectiveness of neutrons for carcinogenesis and the impact that these uncertainties have on second-cancer risk predictions for survivors of adult and childhood cancer who receive proton therapy. © 2009 American Institute of Physics

The Network City

The network approach to urban studies can be differentiated from other approaches by its insistence on the primacy of structures of interpersonal linkages, rather than the classification of social units according to their individual characteristics. Network analysis is an approach, leading to the formulation of particular kinds of questions, such as "who is linked to whom?" and "what is the structure and content of their relational network;" at the same time it is a methodology for their investigation. Following a discussion of network analytic methods, several of the key issues in urban studies are investigated from this perspective. Interpersonal ties in the city, migration, resource allocation, neighborhood and community are examined in terms of the network structures and processes that order and integrate urban activities. These structures and processes reveal themselves to be ever more complex and extensive at each level of the investigation. A view of the city itself as a network of networks is proposed. It is the organization of urban life by networks that makes the scale and diversity of the city a source of strength rather than chaos, while it is precisely that scale and diversity which makes the complex and widely-ramified network structures possible. The flexibility inherent in network structures can accommodate a variety of situations, while variations in the content and intensity of network linkages allows for the co-ordination and integration of widely different people and activities. It is the structural and processual adaptability of networks which fits them so admirably for their role as a central organizing principle in urban life