Towards Data Mining in Large and Fully Distributed Peer-To-Peer Overlay Networks

The Internet, which is becoming a more and more dynamic, extremely heterogeneous network has recently became a platform for huge fully distributed peer-to-peer overlay networks containing millions of nodes typically for the purpose of information dissemination and file sharing. This paper targets the problem of analyzing data which are scattered over a such huge and dynamic set of nodes, where each node is storing possibly very little data but where the total amount of data is immense due to the large number of nodes. We present distributed algorithms for effectively calculating basic statistics of data using the recently introduced newscast model of computation and we demonstrate how to implement basic data mining algorithms based on these techniques. We will argue that the suggested techniques are efficient, robust and scalable and that they preserve the privacy of data

Classification of Low Dimensional Lie Super-Bialgebras

A thorough analysis of Lie super-bialgebra structures on Lie super-algebras osp(1|2) and super-e(2) is presented. Combined technique of computer algebraic computations and a subsequent identification of equivalent structures is applied. In all the cases Poisson-Lie brackets on supergroups are found. Possibility of quantizing them in order to obtain quantum groups is discussed. It turns out to be straightforward for all but one structures for super-E(2) group.Comment: 15 pages, LaTe

Adventures of a tidally induced bar

Using N-body simulations, we study the properties of a bar induced in a discy dwarf galaxy as a result of tidal interaction with the Milky Way. The bar forms at the first pericentre passage and survives until the end of the evolution at 10 Gyr. Fourier decomposition of the bar reveals that only even modes are significant and preserve a hierarchy so that the bar mode is always the strongest. They show a characteristic profile with a maximum, similar to simulated bars forming in isolated galaxies and observed bars in real galaxies. We adopt the maximum of the bar mode as a measure of the bar strength and we estimate the bar length by comparing the density profiles along the bar and perpendicular to it. The bar strength and the bar length decrease with time, mainly at pericentres, as a result of tidal torques acting at those times and not to secular evolution. The pattern speed of the bar varies significantly on a time-scale of 1 Gyr and is controlled by the orientation of the tidal torque from the Milky Way. The bar is never tidally locked, but we discover a hint of a 5/2 orbital resonance between the third and fourth pericentre passage. The speed of the bar decreases in the long run so that the bar changes from initially rather fast to slow in the later stages. The boxy/peanut shape is present for some time and its occurrence is preceded by a short period of buckling instability

What senior academics can do to support reproducible and open research: a short, three-step guide

Increasingly, policies are being introduced to reward and recognise open research practices, while the adoption of such practices into research routines is being facilitated by many grassroots initiatives. However, despite this widespread endorsement and support, open research is yet to be widely adopted, with early career researchers being the notable exception. For open research to become the norm, initiatives should engage academics from all career stages, particularly senior academics (namely senior lecturers, readers, professors) given their routine involvement in determining the quality of research. Senior academics, however, face unique challenges in implementing policy change and supporting grassroots initiatives. Given that - like all researchers - senior academics are in part motivated by self-interest, this paper lays out three feasible steps that senior academics can take to improve the quality and productivity of their research, that also serve to engender open research. These steps include a) change hiring criteria, b) change how scholarly outputs are credited, and c) change to funding and publishing with open research. The guidance we provide is accompanied by live, crowd-sourced material for further reading

148. Changes in lateral dimensions of irradiated volume and their impact on the accuracy of dose delivery during radiotherapy for head and neck cancer

AimTo assess changes in lateral dimensions of irradiated volume during head and neck cancer radiotherapy and their impact on dose delivery accuracy.Material and methodsLateral dimensions of irradiated volumes were measured in 5 predefined points using computed tomography, simulator and manually with calipers, prior to treatment and then bi-weekly. For each measurement reference point dose was calculated and verified using in vivo dosimetry. Early radiation reactions, patient's weight changes and the need to modify radiotherapy accessories were also assessed. All these parameters were analyzed in relation to tumor site and stage, treatment field size, radiation dose and the degree of radiation reactions.ResultsThe study included 33 head and neck cancer patients (24 men and 9 women) aged 24–77 (median 56). All patients were irradiated using the parallel opposed megavoltage fields ranging from 49 to 180 cm2 (median 121 cm2) to the dose of 44 to 80 Gy (median 66 Gy). Radiation reactions included mucositis (grade 3 – 1 patient, grade 2 – 17 patients, grade 1 – 13 patients) and dysphagia (grade 2 – 12 patients, grade 1 – 16 patients). The body mass changes during radiotherapy ranged from −18 to +4 kg (median −5 kg). In 1 patient radiotherapy accessories had to be modified three times during the treatment, in 6 – twice and in 10 – once. Lateral dimensions changes >5 mm occurred in all but one patient (range −37 to +16 mm). Theoretical doses calculated for changed dimensions varied from prescribed by −2.5% to +6% (median +2%). Differences larger than 5% were present in 4.8% of calculations. In vivo dose measurements (after introduction of necessary corrections) demonstrated difference from prescribed dose larger than 5% in 7.6% of measurements.ConclusionChanges in the lateral dimensions of irradiated volume during head and neck cancer radiotherapy may lead to some inaccuracies in delivered doses. Such situations may necessitate adequate corrections of dose calculations and modification of radiotherapy accessories during the course of treatment

Lie Bialgebra Structures for Centrally Extended Two- Dimensional Galilei Algebra and their Lie-Poisson Counterparts

All bialgebra structures for centrally extended Galilei algebra are classified. The corresponding Lie-Poisson structures on centrally extended Galilei group are found.Comment: Eq. (11) changed, 15 pages, LaTeX fil

Risk perceptions, sexual attitudes, and sexual behavior after HPV vaccination in 11-12 year-old girls

OBJECTIVES: Among 11-12 year-old girls who received the human papillomavirus (HPV) vaccine, we explored, over the subsequent 30 months: (1) trajectories of knowledge about HPV/HPV vaccines and vaccine-related risk perceptions; (2) whether knowledge and risk perceptions impacted sexual attitudes and sexual experience; (3) whether mothers, clinicians, and media influenced girls' risk perceptions, attitudes, and behavior. METHODS: Girls and mothers (n=25dyads) completed separate, semi-structured interviews within 2 days of, and 6, 18, and 30 months after, their first HPV vaccine dose. Knowledge, risk perceptions related to HPV and other sexually transmitted infections (STIs), and attitudes about sexual behaviors were assessed. Sexual experience was assessed at girls' 30 month interviews. Clinicians completed interviews at baseline. Transcribed interviews were analyzed using framework analysis. RESULTS: Girls' baseline knowledge was poor but often improved with time. Most girls (n=18) developed accurate risk perceptions about HPV but only half (n=12) developed accurate risk perceptions about other STIs by 30 months. The vast majority of girls thought that safer sex was still important, regardless of knowledge, risk perceptions, or sexual experience. Girls whose HPV knowledge was high at baseline or increased over time tended to articulate accurate risk perceptions; those who were able to articulate accurate risk perceptions tended to report not having initiated sexual activity. Girls whose mothers demonstrated higher knowledge and/or communication about HPV vaccination tended to articulate accurate risk perceptions, whereas clinicians and media exposure did not appear to influence risk perceptions. CONCLUSIONS: Higher knowledge about HPV vaccines among mothers and girls was linked with more accurate risk perceptions among girls. Clinicians may play an important role in providing education about HPV vaccines to mothers and girls

Quantum (1+1) extended Galilei algebras: from Lie bialgebras to quantum R-matrices and integrable systems

The Lie bialgebras of the (1+1) extended Galilei algebra are obtained and classified into four multiparametric families. Their quantum deformations are obtained, together with the corresponding deformed Casimir operators. For the coboundary cases quantum universal R-matrices are also given. Applications of the quantum extended Galilei algebras to classical integrable systems are explicitly developed.Comment: 16 pages, LaTeX. A detailed description of the construction of integrable systems is carried ou