784 research outputs found

    Prospects for Observing an Invisibly Decaying Higgs Boson in ttˉHt\bar{t}H Production at the LHC

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    In this thesis we study the prospects for observing the invisibly decaying Higgs boson in the associated ttˉHt\bar tH production at the LHC. The results of the Monte Carlo simulations of signal and background processes show that there is a possibility of observing the statistically significant number of signal events required for the discovery. Moreover, the analysis can be further improved to reduce the number of false reconstructions of the WW boson. The analysis of the ttˉHt \bar t H production is independent of the model in which the Higgs boson decays into the invisible channel. There are several possibilities for models where H→invisibleH\to invisible can be of interest. For this thesis, we have studied the simplest supersymmetric model, called mSUGRA. The results of the scans of the mSUGRA model parameter space show that the regions, where the branching ratio of the lightest neutral Higgs boson to the lightest neutralino pair is high, are excluded by current experimental constraints. The h→bbˉh \to b \bar b channel dominates, and the possibility for discovery in this c hannel will not be suppressed by the invisible decays. This result does not disqualify invisible channel as possible signature in other models. Chapter 4 of this thesis is based on the published paper: B.P. Kersevan, \underline{M. Malawski}, E. Richter-Was: {\em Prospects for observing an invisibly decaying Higgs boson in the ttˉHt\bar t H production at the LHC}, The European Physical Journal C - Particles and Fields, 2003, vol. 29, no. 4, pp. 541 - 548.Comment: Master of Science Thesi

    Serverless Computing for Scientific Applications

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    Serverless computing has become an important model in cloud computing and influenced the design of many applications. Here, we provide our perspective on how the recent landscape of serverless computing for scientific applications looks like. We discuss the advantages and problems with serverless computing for scientific applications, and based on the analysis of existing solutions and approaches, we propose a science-oriented architecture for a serverless computing framework that is based on the existing designs. Finally, we provide an outlook of current trends and future directions

    Flexible And Secure Access To Computing Clusters

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    The investigation presented in this paper was prompted by the need to provide a manageablesolution for secure access to computing clusters with a federated authentication framework.This requirement is especially important for scientists who need direct access to computingnodes in order to run their applications (e.g. chemical or medical simulations) with proprietary,open-source or custom-developed software packages. Our existing software, whichenables non-Web clients to use Shibboleth-secured services, has been extended to providedirect SSH access to cluster nodes using the Linux Pluggable Authentication Modules mechanism.This allows Shibboleth users to run the required software on clusters. Validationand performance comparison with existing SSH authentication mechanisms confirm that thepresented tools satisfy the stated requirements

    Using Unused: Non-Invasive Dynamic FaaS Infrastructure with HPC-Whisk

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    Modern HPC workload managers and their careful tuning contribute to the high utilization of HPC clusters. However, due to inevitable uncertainty it is impossible to completely avoid node idleness. Although such idle slots are usually too short for any HPC job, they are too long to ignore them. Function-as-a-Service (FaaS) paradigm promisingly fills this gap, and can be a good match, as typical FaaS functions last seconds, not hours. Here we show how to build a FaaS infrastructure on idle nodes in an HPC cluster in such a way that it does not affect the performance of the HPC jobs significantly. We dynamically adapt to a changing set of idle physical machines, by integrating open-source software Slurm and OpenWhisk. We designed and implemented a prototype solution that allowed us to cover up to 90\% of the idle time slots on a 50k-core cluster that runs production workloads

    Virtual patients in a behavioral medicine massive open online course (MOOC) : a case-based analysis of technical capacity and user navigation pathways

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    BACKGROUND: Massive open online courses (MOOCs) have been criticized for focusing on presentation of short video clip lectures and asking theoretical multiple-choice questions. A potential way of vitalizing these educational activities in the health sciences is to introduce virtual patients. Experiences from such extensions in MOOCs have not previously been reported in the literature. OBJECTIVE: This study analyzes technical challenges and solutions for offering virtual patients in health-related MOOCs and describes patterns of virtual patient use in one such course. Our aims are to reduce the technical uncertainty related to these extensions, point to aspects that could be optimized for a better learner experience, and raise prospective research questions by describing indicators of virtual patient use on a massive scale. METHODS: The Behavioral Medicine MOOC was offered by Karolinska Institutet, a medical university, on the EdX platform in the autumn of 2014. Course content was enhanced by two virtual patient scenarios presented in the OpenLabyrinth system and hosted on the VPH-Share cloud infrastructure. We analyzed web server and session logs and a participant satisfaction survey. Navigation pathways were summarized using a visual analytics tool developed for the purpose of this study. RESULTS: The number of course enrollments reached 19,236. At the official closing date, 2317 participants (12.1% of total enrollment) had declared completing the first virtual patient assignment and 1640 (8.5%) participants confirmed completion of the second virtual patient assignment. Peak activity involved 359 user sessions per day. The OpenLabyrinth system, deployed on four virtual servers, coped well with the workload. Participant survey respondents (n=479) regarded the activity as a helpful exercise in the course (83.1%). Technical challenges reported involved poor or restricted access to videos in certain areas of the world and occasional problems with lost sessions. The visual analyses of user pathways display the parts of virtual patient scenarios that elicited less interest and may have been perceived as nonchallenging options. Analyzing the user navigation pathways allowed us to detect indications of both surface and deep approaches to the content material among the MOOC participants. CONCLUSIONS: This study reported on first inclusion of virtual patients in a MOOC. It adds to the body of knowledge by demonstrating how a biomedical cloud provider service can ensure technical capacity and flexible design of a virtual patient platform on a massive scale. The study also presents a new way of analyzing the use of branched virtual patients by visualization of user navigation pathways. Suggestions are offered on improvements to the design of virtual patients in MOOCs

    Never born proteins as a test case for ab initio protein structures prediction

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    The number of natural proteins although large is significantly smaller than the theoretical number of proteins that can be obtained combining the 20 natural amino acids, the so-called “never born proteins” (NBPs). The study of the structure and properties of these proteins allows to investigate the sources of the natural proteins being of unique characteristics or special properties. However the structural study of NPBs can also been intended as an ideal test for evaluating the efficiency of software packages for the ab initio protein structure prediction. In this research, 10.000 three-dimensional structures of proteins of completely random sequence generated according to ROSETTA and FOD model were compared. The results show the limits of these software packages, but at the same time indicate that in many cases there is a significant agreement between the prediction obtained

    A Platform for Collaborative e-Science Applications

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    Abstract A novel, holistic, approach to scientific investigations should, besides analysis of individual phenomena, integrate different, interdisciplinary sources of knowledge about a complex system to obtain a deep understanding of the system as a whole. This innovative way of research, recently called system-level science [1], requires advanced software environments to support collaborating research groups. Most problem-solving environments and virtual laboratories In the ViroLab project The Virtual Laboratory (see The Experiment Planning Environment supports rapid experiment plan development while the Experiment Management Interface enables loading and execution of experiments. The Experiment Repository developers and published for future use. The virtual laboratory engi Operation Invoker which instantiates grid object repr operation invocations. The GridSpace Applic load balancing on computational servers. The Data Access Service remote databases located in research institutions and Fig. 1. Architecture of the Virtual Laboratory The provenance approach in the ViroLab virtual laboratory ontology-based semantic modeling, monitoring of infrastructure, and database technologies, in order to coll the execution of experiments, represent it in a meaningful way, repository. In the ViroLab project, this virtual laboratory is used to plan and virological experiments, with various types of analysis of as the calculation of drug resistance, querying historical and about experiments, a drug resistance system based on the Retrogram been applied to other application domains, such as comparison, data mining using the Weka library, series of Gaussian application on the EGEE infrastructure. computer science classes. We have developed an environment for collaborative planning, execution of e-Science applications. It facilitates fast, close cooperation and users so it may be used by groups of experts running In-silico experiments undergo frequent changes, this platform encourages quick, agile simulation software releasing

    Search for Physics beyond the Standard Model in Events with Overlapping Photons and Jets

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    Results are reported from a search for new particles that decay into a photon and two gluons, in events with jets. Novel jet substructure techniques are developed that allow photons to be identified in an environment densely populated with hadrons. The analyzed proton-proton collision data were collected by the CMS experiment at the LHC, in 2016 at root s = 13 TeV, and correspond to an integrated luminosity of 35.9 fb(-1). The spectra of total transverse hadronic energy of candidate events are examined for deviations from the standard model predictions. No statistically significant excess is observed over the expected background. The first cross section limits on new physics processes resulting in such events are set. The results are interpreted as upper limits on the rate of gluino pair production, utilizing a simplified stealth supersymmetry model. The excluded gluino masses extend up to 1.7 TeV, for a neutralino mass of 200 GeV and exceed previous mass constraints set by analyses targeting events with isolated photons.Peer reviewe

    Measurement of the Jet Mass Distribution and Top Quark Mass in Hadronic Decays of Boosted Top Quarks in pp Collisions at root s=13 TeV