Guaranteed clustering and biclustering via semidefinite programming

Identifying clusters of similar objects in data plays a significant role in a wide range of applications. As a model problem for clustering, we consider the densest k-disjoint-clique problem, whose goal is to identify the collection of k disjoint cliques of a given weighted complete graph maximizing the sum of the densities of the complete subgraphs induced by these cliques. In this paper, we establish conditions ensuring exact recovery of the densest k cliques of a given graph from the optimal solution of a particular semidefinite program. In particular, the semidefinite relaxation is exact for input graphs corresponding to data consisting of k large, distinct clusters and a smaller number of outliers. This approach also yields a semidefinite relaxation for the biclustering problem with similar recovery guarantees. Given a set of objects and a set of features exhibited by these objects, biclustering seeks to simultaneously group the objects and features according to their expression levels. This problem may be posed as partitioning the nodes of a weighted bipartite complete graph such that the sum of the densities of the resulting bipartite complete subgraphs is maximized. As in our analysis of the densest k-disjoint-clique problem, we show that the correct partition of the objects and features can be recovered from the optimal solution of a semidefinite program in the case that the given data consists of several disjoint sets of objects exhibiting similar features. Empirical evidence from numerical experiments supporting these theoretical guarantees is also provided

Обеспечение радиационной безопасности при выводе из эксплуатации тяжеловодного исследовательского ядерного реактора НИЦ «Курчатовский институт» – ИТЭФ

The article provides a brief description of organizational and technical measures aimed at ensuring radiation safety during the decommissioning of the heavy-water research nuclear reactor of Institute for Theoretical and Experimental Physics after A.I. Alikhanov of National Research Centre «Kurchatov Institute». Information is provided on the history and features of the operation of the reactor, including parameters and characteristics that are significant for planning and conducting work. The peculiarities of legal regulation in the field of ensuring radiation safety are given; regulatory acts and rules accompanying other activities during decommissioning and directly related to radiation safety are also considered. The paper describes the work done in preparation for dismantling, the initial and current state of the installation, forthcoming work with examples of dismantled equipment. Methods for handling radioactive waste arising during decommissioning are considered, including methods for fragmentation of large structural elements (examples of mechanical devices are given), methods for sorting according to different specific activity (high activity, low activity), radionuclide composition and physical properties (solid, metallic, non-metallic, liquid). A special method for handling liquid radioactive waste is described, which includes the collection and temporary storage system. To assess the radiation situation at workplaces during the dismantling of the reactor structures, calculations of radiation transfer were carried out on the running and shutdown reactor, during which it was established that the expected dose to the personnel when performing activities on decommissioning of TBR is much lower than the limit values, established by regulatory documents. In accordance with the estimated radiation doses, rules and instructions for personnel were determined, including the procedure for using personal protective equipment, the necessary measures for surface decontamination, etc. Information is given on the procedure for radiation monitoring at all stages of dismantling and at the final stages of decommissioning including control of premises, personnel, equipment, waste of various types, atmospheric air.В статье приведено краткое описание организационных и технических мер, направленных на обеспечение радиационной безопасности при выводе из эксплуатации тяжеловодного исследовательского ядерного реактора Института теоретической и экспериментальной физики имени А.И. Алиханова Национального исследовательского центра «Курчатовский институт». Представлена информация об истории и особенностях эксплуатации реактора, в том числе параметры и характеристики, значимые для планирования и проведения работ. Приведены особенности нормативно-правового регулирования в области обеспечения радиационной безопасности, также рассмотрены нормативные акты и правила, сопутствующие прочим работам при выводе из эксплуатации и непосредственно связанные с радиационной безопасностью. Описаны выполненные работы по подготовке к демонтажу, исходное и текущее состояние установки, предстоящие работы с приведением примеров демонтируемого оборудования. Рассмотрены методы обращения с радиоактивными отходами, возникающими в ходе работ по выводу из эксплуатации, в том числе способы фрагментации крупных элементов конструкций (приведены примеры механических устройств), способы сортировки в соответствии с различной удельной активностью (высокоактивные, низкоактивные), радионуклидным составом и физическими свойствами (твердые, металлические, неметаллические, жидкие). Приведена информация о порядке радиационного контроля на всех этапах работ по демонтажу и на заключительных этапах вывода из эксплуатации, включая контроль помещений, персонала, оборудования, отходов различного типа, атмосферного воздуха

Dermacentor reticulatus: a vector on the rise

Dermacentor reticulatus is a hard tick species with extraordinary biological features. It has a high reproduction rate, a rapid developmental cycle, and is also able to overcome years of unfavourable conditions. Dermacentor reticulatus can survive under water for several months and is cold-hardy even compared to other tick species. It has a wide host range: over 60 different wild and domesticated hosts are known for the three active developmental stages. Its high adaptiveness gives an edge to this tick species as shown by new data on the emergence and establishment of D. reticulatus populations throughout Europe. The tick has been the research focus of a growing number of scientists, physicians and veterinarians. Within the Web of Science database, more than a fifth of the over 700 items published on this species between 1897 and 2015 appeared in the last three years (2013–2015). Here we attempt to synthesize current knowledge on the systematics, ecology, geographical distribution and recent spread of the species and to highlight the great spectrum of possible veterinary and public health threats it poses. Canine babesiosis caused by Babesia canis is a severe leading canine vector-borne disease in many endemic areas. Although less frequently than Ixodes ricinus, D. reticulatus adults bite humans and transmit several Rickettsia spp., Omsk haemorrhagic fever virus or Tick-borne encephalitis virus. We have not solely collected and reviewed the latest and fundamental scientific papers available in primary databases but also widened our scope to books, theses, conference papers and specialists colleagues’ experience where needed. Besides the dominant literature available in English, we also tried to access scientific literature in German, Russian and eastern European languages as well. We hope to inspire future research projects that are necessary to understand the basic life-cycle and ecology of this vector in order to understand and prevent disease threats. We conclude that although great strides have been made in our knowledge of the eco-epidemiology of this species, several gaps still need to be filled with basic research, targeting possible reservoir and vector roles and the key factors resulting in the observed geographical spread of D. reticulatus. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1599-x) contains supplementary material, which is available to authorized users

Provision of the radiation safety for the decomissioning of the heavy-water research nuclear reactor NRC «Kurchatov Institute» – ITEP

The article provides a brief description of organizational and technical measures aimed at ensuring radiation safety during the decommissioning of the heavy-water research nuclear reactor of Institute for Theoretical and Experimental Physics after A.I. Alikhanov of National Research Centre «Kurchatov Institute». Information is provided on the history and features of the operation of the reactor, including parameters and characteristics that are significant for planning and conducting work. The peculiarities of legal regulation in the field of ensuring radiation safety are given; regulatory acts and rules accompanying other activities during decommissioning and directly related to radiation safety are also considered. The paper describes the work done in preparation for dismantling, the initial and current state of the installation, forthcoming work with examples of dismantled equipment. Methods for handling radioactive waste arising during decommissioning are considered, including methods for fragmentation of large structural elements (examples of mechanical devices are given), methods for sorting according to different specific activity (high activity, low activity), radionuclide composition and physical properties (solid, metallic, non-metallic, liquid). A special method for handling liquid radioactive waste is described, which includes the collection and temporary storage system. To assess the radiation situation at workplaces during the dismantling of the reactor structures, calculations of radiation transfer were carried out on the running and shutdown reactor, during which it was established that the expected dose to the personnel when performing activities on decommissioning of TBR is much lower than the limit values, established by regulatory documents. In accordance with the estimated radiation doses, rules and instructions for personnel were determined, including the procedure for using personal protective equipment, the necessary measures for surface decontamination, etc. Information is given on the procedure for radiation monitoring at all stages of dismantling and at the final stages of decommissioning including control of premises, personnel, equipment, waste of various types, atmospheric air