SwePub - search: WFRF:(Seif M)

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1.	Thomas, HS, et al. (author) 2019 swepub:Mat__t
2.	Bhangu, A, et al. (author) Mortality of emergency abdominal surgery in high-, middle- and low-income countries 2016 In: The British journal of surgery. - : Oxford University Press (OUP). - 1365-2168 .- 0007-1323. ; 103:8, s. 971-988 Journal article (peer-reviewed)
3.	Ademuyiwa, Adesoji O., et al. (author) Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries 2016 In: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4 Journal article (peer-reviewed)abstract Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
4.	Amole, C., et al. (author) The ALPHA antihydrogen trapping apparatus 2014 In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 735, s. 319-340 Journal article (peer-reviewed)abstract The ALPHA collaboration, based at CERN, has recently succeeded in confining cold antihydrogen atoms in a magnetic minimum neutral atom trap and has performed the first study of a resonant transition of the anti-atoms. The ALPHA apparatus will be described herein, with emphasis on the structural aspects, diagnostic methods and techniques that have enabled antihydrogen trapping and experimentation to be achieved.
5.	Andresen, G. B., et al. (author) The ALPHA-detector : Module Production and Assembly 2012 In: Journal of Instrumentation. - 1748-0221. ; 7, s. C01051- Journal article (peer-reviewed)abstract ALPHA is one of the experiments situated at CERN's Antiproton Decelerator (AD). A Silicon Vertex Detector (SVD) is placed to surround the ALPHA atom trap. The main purpose of the SVD is to detect and locate antiproton annihilation events by means of the emitted charged pions. The SVD system is presented with special focus given to the design, fabrication and performance of the modules.
6.	Andresen, G. B., et al. (author) Trapped antihydrogen 2010 In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 468:7324, s. 673-676 Journal article (peer-reviewed)abstract Antimatter was first predicted1 in 1931, by Dirac. Work with high-energy antiparticles is now commonplace, and anti-electrons are used regularly in the medical technique of positron emission tomography scanning. Antihydrogen, the bound state of an antiproton and a positron, has been produced2, 3 at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. The charge conjugation/parity/time reversal (CPT) theorem, a crucial part of the foundation of the standard model of elementary particles and interactions, demands that hydrogen and antihydrogen have the same spectrum. Given the current experimental precision of measurements on the hydrogen atom (about two parts in 1014 for the frequency of the 1s-to-2s transition4), subjecting antihydrogen to rigorous spectroscopic examination would constitute a compelling, model-independent test of CPT. Antihydrogen could also be used to study the gravitational behaviour of antimatter5. However, so far experiments have produced antihydrogen that is not confined, precluding detailed study of its structure. Here we demonstrate trapping of antihydrogen atoms. From the interaction of about 107 antiprotons and 7 × 108 positrons, we observed 38 annihilation events consistent with the controlled release of trapped antihydrogen from our magnetic trap; the measured background is 1.4 ± 1.4 events. This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.
7.	Andresen, G. B., et al. (author) Search for trapped antihydrogen 2011 In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 95-104 Journal article (peer-reviewed)abstract We present the results of an experiment to search for trapped antihydrogen atoms with the ALPHA antihydrogen trap at the CERN Antiproton Decelerator. Sensitive diagnostics of the temperatures, sizes, and densities of the trapped antiproton and positron plasmas have been developed, which in turn permitted development of techniques to precisely and reproducibly control the initial experimental parameters. The use of a position-sensitive annihilation vertex detector, together with the capability of controllably quenching the superconducting magnetic minimum trap, enabled us to carry out a high-sensitivity and low-background search for trapped synthesised antihydrogen atoms. We aim to identify the annihilations of antihydrogen atoms held for at least 130 ms in the trap before being released over ~30 ms. After a three-week experimental run in 2009 involving mixing of 107 antiprotons with 1.3ï¿œ109 positrons to produce 6ï¿œ105 antihydrogen atoms, we have identified six antiproton annihilation events that are consistent with the release of trapped antihydrogen. The cosmic ray background, estimated to contribute 0.14 counts, is incompatible with this observation at a significance of 5.6 sigma. Extensive simulations predict that an alternative source of annihilations, the escape of mirror-trapped antiprotons, is highly unlikely, though this possibility has not yet been ruled out experimentally.
8.	Charlton, M, et al. (author) Antiparticle sources for antihydrogen production and trapping 2011 In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596. ; 262, s. 012001- Journal article (peer-reviewed)abstract Sources of positrons and antiprotons that are currently used for the formation of antihydrogen with low kinetic energies are reviewed, mostly in the context of the ALPHA collaboration and its predecessor ATHENA. The experiments were undertaken at the Antiproton Decelerator facility, which is located at CERN. Operations performed on the clouds of antiparticles to facilitate their mixing to produce antihydrogen are described. These include accumulation, cooling and manipulation. The formation of antihydrogen and some of the characteristics of the anti-atoms that are created are discussed. Prospects for trapping antihydrogen in a magnetic minimum trap, as envisaged by the ALPHA collaboration, are reviewed.
9.	Madsen, N, et al. (author) Search for trapped antihydrogen in ALPHA 2011 In: Canadian journal of physics (Print). - 0008-4204 .- 1208-6045. ; 89:1, s. 7-16 Journal article (peer-reviewed)abstract Antihydrogen spectroscopy promises precise tests of the symmetry of matter and antimatter, and can possibly offer new insights into the baryon asymmetry of the universe. Antihydrogen is, however, difficult to synthesize and is produced only in small quantities. The ALPHA collaboration is therefore pursuing a path towards trapping cold antihydrogen to permit the use of precision atomic physics tools to carry out comparisons of antihydrogen and hydrogen. ALPHA has addressed these challenges. Control of the plasma sizes has helped to lower the influence of the multipole field used in the neutral atom trap, and thus lowered the temperature of the created atoms. Finally, the first systematic attempt to identify trapped antihydrogen in our system is discussed. This discussion includes special techniques for fast release of the trapped anti-atoms, as well as a silicon vertex detector to identify antiproton annihilations. The silicon detector reduces the background of annihilations, including background from antiprotons that can be mirror trapped in the fields of the neutral atom trap. A description of how to differentiate between these events and those resulting from trapped antihydrogen atoms is also included.
10.	Andresen, G. B., et al. (author) Antihydrogen annihilation reconstruction with the ALPHA silicon detector 2012 In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 684, s. 73-81 Journal article (peer-reviewed)abstract The ALPHA experiment has succeeded in trapping antihydrogen, a major milestone on the road to spectroscopic comparisons of antihydrogen with hydrogen. An annihilation vertex detector, which determines the time and position of antiproton annihilations, has been central to this achievement. This detector, an array of double-sided silicon microstrip detector modules arranged in three concentric cylindrical tiers, is sensitive to the passage of charged particles resulting from antiproton annihilation. This article describes the method used to reconstruct the annihilation location and to distinguish the annihilation signal from the cosmic ray background. Recent experimental results using this detector are outlined.
11.	Repapi, Emmanouela, et al. (author) Genome-wide association study identifies five loci associated with lung function. 2010 In: Nature genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 42:1, s. 36-44 Journal article (peer-reviewed)abstract Pulmonary function measures are heritable traits that predict morbidity and mortality and define chronic obstructive pulmonary disease (COPD). We tested genome-wide association with forced expiratory volume in 1 s (FEV(1)) and the ratio of FEV(1) to forced vital capacity (FVC) in the SpiroMeta consortium (n = 20,288 individuals of European ancestry). We conducted a meta-analysis of top signals with data from direct genotyping (n < or = 32,184 additional individuals) and in silico summary association data from the CHARGE Consortium (n = 21,209) and the Health 2000 survey (n < or = 883). We confirmed the reported locus at 4q31 and identified associations with FEV(1) or FEV(1)/FVC and common variants at five additional loci: 2q35 in TNS1 (P = 1.11 x 10(-12)), 4q24 in GSTCD (2.18 x 10(-23)), 5q33 in HTR4 (P = 4.29 x 10(-9)), 6p21 in AGER (P = 3.07 x 10(-15)) and 15q23 in THSD4 (P = 7.24 x 10(-15)). mRNA analyses showed expression of TNS1, GSTCD, AGER, HTR4 and THSD4 in human lung tissue. These associations offer mechanistic insight into pulmonary function regulation and indicate potential targets for interventions to alleviate respiratory disease.
12.	Soler Artigas, María, et al. (author) Effect of five genetic variants associated with lung function on the risk of chronic obstructive lung disease, and their joint effects on lung function. 2011 In: American journal of respiratory and critical care medicine. - 1535-4970. ; 184:7, s. 786-95 Journal article (peer-reviewed)abstract Genomic loci are associated with FEV1 or the ratio of FEV1 to FVC in population samples, but their association with chronic obstructive pulmonary disease (COPD) has not yet been proven, nor have their combined effects on lung function and COPD been studied.
13.	el-Din, Sayed H. Seif, et al. (author) Potential effect of the medicinal plants Calotropis procera, Ficus elastica and Zingiber officinale against Schistosoma mansoni in mice 2014 In: Pharmaceutical Biology. - : Informa UK Limited. - 1744-5116 .- 1388-0209. ; 52:2, s. 144-150 Journal article (peer-reviewed)abstract Context: Calotropis procera (Ait.) R. Br. (Asclepiadaceae), Ficus elastica Roxb. (Moraceae) and Zingiber officinale Roscoe (Zingiberaceae) have been traditionally used to treat many diseases. Objective: The antischistosomal activity of these plant extracts was evaluated against Schistosoma mansoni. Materials and methods: Male mice exposed to 80 +/- 10 cercariae per mouse were divided into two batches. The first was divided into five groups: (I) infected untreated, while groups from (II-V) were treated orally (500 mg/kg for three consecutive days) by aqueous stem latex and flowers of C. procera, latex of F. elastica and ether extract of Z. officinale, respectively. The second batch was divided into four comparable groups (except Z. officinale-treated group) similarly treated as the first batch in addition to the antacid ranitidine (30 mg/kg) 1 h before extract administration. Safety, worm recovery, tissues egg load and oogram pattern were assessed. Results: Calotropis procera latex and flower extracts are toxic (50-70% mortality) even in a small dose (250 mg/kg) before washing off their toxic rubber. Zingiber officinale extract insignificantly decrease (7.26%) S. mansoni worms. When toxic rubber was washed off and ranitidine was used, C. procera (stem latex and flowers) and F. elastica extracts revealed significant S. mansoni worm reductions by 45.31, 53.7 and 16.71%, respectively. Moreover, C. procera extracts produced significant reductions in tissue egg load (similar to 34-38.5%) and positively affected oogram pattern. Conclusion: The present study may be useful to supplement information with regard to C. procera and F. elastica antischistosomal activity and provide a basis for further experimental trials.
14.	Koubarakis, M., et al. (author) From copernicus big data to extreme earth analytics 2019 In: Advances in Database Technology - EDBT. - : OpenProceedings. - 9783893180813 ; , s. 690-693 Conference paper (peer-reviewed)abstract Copernicus is the European programme for monitoring the Earth. It consists of a set of systems that collect data from satellites and in-situ sensors, process this data and provide users with reliable and up-to-date information on a range of environmental and security issues. The data and information processed and disseminated puts Copernicus at the forefront of the big data paradigm, giving rise to all relevant challenges, the so-called 5 Vs: volume, velocity, variety, veracity and value. In this short paper, we discuss the challenges of extracting information and knowledge from huge archives of Copernicus data. We propose to achieve this by scale-out distributed deep learning techniques that run on very big clusters offering virtual machines and GPUs. We also discuss the challenges of achieving scalability in the management of the extreme volumes of information and knowledge extracted from Copernicus data. The envisioned scientific and technical work will be carried out in the context of the H2020 project ExtremeEarth which starts in January 2019.
15.	Sawicki, J., et al. (author) Perspectives on adaptive dynamical systems 2023 In: Chaos. - 1054-1500 .- 1089-7682. ; 33:7 Journal article (peer-reviewed)abstract Adaptivity is a dynamical feature that is omnipresent in nature, socio-economics, and technology. For example, adaptive couplings appear in various real-world systems, such as the power grid, social, and neural networks, and they form the backbone of closed-loop control strategies and machine learning algorithms. In this article, we provide an interdisciplinary perspective on adaptive systems. We reflect on the notion and terminology of adaptivity in different disciplines and discuss which role adaptivity plays for various fields. We highlight common open challenges and give perspectives on future research directions, looking to inspire interdisciplinary approaches.
16.	Seif, M. R., et al. (author) Polynomial approximation for fast generation of associated Legendre functions 2018 In: Acta Geodaetica et Geophysica. - : Springer. - 2213-5812 .- 2213-5820. ; 53:2, s. 275-293 Journal article (peer-reviewed)abstract Today high-speed computers have simplified many computational problems, but fast techniques and algorithms are still relevant. In this study, the Hermitian polynomial approximation is used for fast evaluation of the associated Legendre functions (ALFs). It has lots of applications in geodesy and geophysics. This method approximates the ALFs instead of computing them by recursive formulae and generate them several times faster. The approximated ALFs by the Newtonian polynomials are compared with Hermitian ones and their differences are discussed. Here, this approach is applied for computing a global geoid model point-wise from EGM08 to degree and order 2160 and in propagating the orbit of a low Earth orbiting satellite. Our numerical results show that the CPU-time decreases at least two times for orbit propagation, and five times for geoid computation comparing to the case where recursive formulae for generation of ALFs are used. The approximation error in the orbit computation is at a sub-millimeter level over two weeks and that the computed geoid 0.01 mm, with a maximum of 1 mm
17.	Arad, Cosmin, et al. (author) Brief Announcement: Atomic Consistency and Partition Tolerance in Scalable Key-Value Stores 2012. - 10 Conference paper (peer-reviewed)
18.	Arad, Cosmin, et al. (author) CATS: linearizability and partition tolerance in scalable and self-organizing key-value stores 2012. - 7 Reports (other academic/artistic)abstract Distributed key-value stores provide scalable, fault-tolerant, and self-organizing storage services, but fall short of guaranteeing linearizable consistency in partially synchronous, lossy, partitionable, and dynamic networks, when data is distributed and replicated automatically by the principle of consistent hashing. This paper introduces consistent quorums as a solution for achieving atomic consistency. We present the design and implementation of CATS, a distributed key-value store which uses consistent quorums to guarantee linearizability and partition tolerance in such adverse and dynamic network conditions. CATS is scalable, elastic, and self-organizing; key properties for modern cloud storage middleware. Our system shows that consistency can be achieved with practical performance and modest throughput overhead (5%) for read-intensive workloads.
19.	Bagheri, Y, et al. (author) Comparison of clinical and immunological features and mortality in common variable immunodeficiency and agammaglobulinemia patients 2019 In: Immunology letters. - : Elsevier BV. - 1879-0542 .- 0165-2478. ; 210, s. 55-62 Journal article (peer-reviewed)
20.	Kavassalis, P., et al. (author) What makes a Web site popular? 2004 In: Communications of the ACM. - : Association for Computing Machinery (ACM). - 0001-0782 .- 1557-7317. ; 47:2, s. 51-55 Journal article (peer-reviewed)abstract Several factors which affect the popularity of the web sites are discussed. A computational model involving two superimposed interaction networks with random connections is developed which links the sites as well as organizes social interactions among internet users. It is suggested that understanding of information flows and connection networks surroundings is necessary to ensure a constant increase in user interest, loyalty and market share. It is also recommended that E-marketers should investigate and leverage the long-term rampifications of information network structures for predicting the behavior of internet users towards their organizations' web sites.
21.	Krause, P, et al. (author) Increased growth of colorectal liver metastasis following partial hepatectomy 2013 In: Clinical and Experimental Metastasis. - : Springer Science and Business Media LLC. - 1573-7276 .- 0262-0898. ; 30:5, s. 681-693 Journal article (peer-reviewed)
22.	Meldrum, M., et al. (author) Arcon : Continuous and deep data stream analytics 2019 In: ACM International Conference Proceeding Series. - New York, NY, USA : Association for Computing Machinery. - 9781450376600 Conference paper (peer-reviewed)abstract Contemporary end-to-end data pipelines need to combine many diverse workloads such as machine learning, relational operations, stream dataflows, tensor transformations, and graphs. For each of these workload types, there exists several frontends (e.g., SQL, Beam, Keras) based on different programming languages as well as different runtimes (e.g., Spark, Flink, Tensorflow) that optimize for a particular frontend and possibly a hardware architecture (e.g., GPUs). The resulting pipelines suffer in terms of complexity and performance due to excessive type conversions, materialization of intermediate results, and lack of cross-framework optimizations. Arcon aims to provide a unified approach to declare and execute tasks across frontend-boundaries as well as enabling their seamless integration with event-driven services at scale. In this demonstration, we present Arcon and through a series of use-case scenarios demonstrate that its execution model is powerful enough to cover existing as well as upcoming real-time computations for analytics and application-specific needs.
23.	Nasrabadi, AN, et al. (author) Night shift work experiences among Iranian nurses: a qualitative study 2009 In: International nursing review. - : Wiley. - 1466-7657 .- 0020-8132. ; 56:4, s. 498-503 Journal article (peer-reviewed)
24.	Rahimian, Fatemeh, et al. (author) A distributed algorithm for large-scale graph partitioning 2015 In: ACM Transactions on Autonomous and Adaptive Systems. - ACM : Association for Computing Machinery. - 1556-4665 .- 1556-4703. ; 10:2 Journal article (peer-reviewed)abstract Balanced graph partitioning is an NP-complete problem with a wide range of applications. These applications include many large-scale distributed problems, including the optimal storage of large sets of graph-structured data over several hosts. However, in very large-scale distributed scenarios, state-of-the-art algorithms are not directly applicable because they typically involve frequent global operations over the entire graph. In this article, we propose a fully distributed algorithm called Ja-be-Ja that uses local search and simulated annealing techniques for two types of graph partitioning: edge-cut partitioning and vertex-cut partitioning. The algorithm is massively parallel: There is no central coordination, each vertex is processed independently, and only the direct neighbors of a vertex and a small subset of random vertices in the graph need to be known locally. Strict synchronization is not required. These features allow Ja-be-Ja to be easily adapted to any distributed graph-processing system from data centers to fully distributed networks. We show that the minimal edge-cut value empirically achieved by Ja-be-Ja is comparable to state-of-the-art centralized algorithms such as Metis. In particular, on large social networks, Ja-be-Ja outperforms Metis. We also show that Ja-be-Ja computes very low vertex-cuts, which are proved significantly more effective than edge-cuts for processing most real-world graphs.
25.	Shafaat, Tallat M., et al. (author) A Practical Approach to Network Size Estimation for Structured Overlays 2008 In: SELF-ORGANIZING SYSTEMS, PROCEEDINGS. - Berlin : SPRINGER-VERLAG. - 9783540921561 ; , s. 71-83 Conference paper (peer-reviewed)abstract Structured overlay networks have recently received much attention due to their self-* properties under dynamic and decentralized settings. The number of nodes in all overlay fluctuates all the time due to churn. Since knowledge of the size of the. overlay is a core requirement for many systems, estimating the size in a decentralized manner is a challenge taken up by recent research activities. Gossip-based Aggregation has been shown to give accurate estimates for the network size, but previous work done is highly sensitive to node failures. In this paper, we present a gossip-based aggregation-style network size estimation algorithm. We discuss shortcomings of existing aggregation-based size estimation algorithms, and give a solution that is highly robust to node failures and is adaptive to network delays. We examine our solution in various scenarios to demonstrate. its effectiveness.
26.	Shafaat, Tallat M., et al. (author) Dealing with network partitions in structured overlay networks 2009 In: Peer-to-Peer Networking and Applications. - : Springer Science and Business Media LLC. - 1936-6442 .- 1936-6450. ; 2:4, s. 334-347 Journal article (peer-reviewed)abstract Structured overlay networks form a major class of peer-to-peer systems, which are touted for their abilities to scale, tolerate failures, and self-manage. Any long-lived Internet-scale distributed system is destined to face network partitions. Although the problem of network partitions and mergers is highly related to fault-tolerance and self-management in large-scale systems, it has hardly been studied in the context of structured peer-to-peer systems. These systems have mainly been studied under churn (frequent joins/failures), which as a side effect solves the problem of network partitions, as it is similar to massive node failures. Yet, the crucial aspect of network mergers has been ignored. In fact, it has been claimed that ring-based structured overlay networks, which constitute the majority of the structured overlays, are intrinsically ill-suited for merging rings. In this paper, we present an algorithm for merging multiple similar ring-based overlays when the underlying network merges. We examine the solution in dynamic conditions, showing how our solution is resilient to churn during the merger, something widely believed to be difficult or impossible. We evaluate the algorithm for various scenarios and show that even when falsely detecting a merger, the algorithm quickly terminates and does not clutter the network with many messages. The algorithm is flexible as the tradeoff between message complexity and time complexity can be adjusted by a parameter.
27.	Shafaat, Tallat M., et al. (author) Dealing with Network Partitions in Structured Overlay Networks 2009. - 5 In: Journal of Peer-to-Peer Networking and Applications (PPNA). Journal article (peer-reviewed)
28.	Shafaat, Tallat M., et al. (author) Handling network partitions and mergers in structured overlay networks 2007 In: P2P. - 9780769529868 ; , s. 132-139 Conference paper (peer-reviewed)abstract Structured overlay networks form a major class of peer-to-peer systems, which are touted for their abilities to scale, tolerate failures, and self-manage. Any long-lived Internet-scale. distributed system is destined to face network partitions. Although the problem of network partitions and mergers is highly related to fault-tolerance and self-management in large-scale systems, it has hardly been studied in the context of structured peer-to-peer systems. These systems have mainly been studied under chum (frequent joins/failures), which as a side effect solves the problem of network partitions, as it is similar to massive node failures. Yet, the crucial aspect of network mergers has been ignored. In fact, it has been claimed that ring-based structured overlay networks, which constitute the majority of the structured overlays, are intrinsically ill-suited for merging rings. In this paper we present an algorithm for merging multiple similar ring-based overlays when the underlying network merges. We examine the solution in dynamic conditions, showing how our solution is resilient to churn during the merger something widely believed to be difficult or impossible. We evaluate the algorithm for various scenarios and show that even when falsely detecting a merger the algorithm quickly terminates and does not clutter the network with many messages. The algorithm is flexible as the tradeoff between message complexity and time complexity can be adjusted by a parameter.
29.	Shafaat, Tallat M., et al. (author) ID-replication for structured peer-to-peer systems 2012 In: Euro-Par 2012 Parallel Processing. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642328190 ; , s. 364-376 Conference paper (peer-reviewed)abstract Structured overlay networks, like any distributed system, use replication to avoid losing data in the presence of failures. In this paper, we discuss the short-comings of existing replication schemes and propose a technique for replication, called ID-Replication. ID-Replication allows different replication degrees for keys in the system, thus allowing popular data to have more copies. We discuss how ID-Replication is less sensitive to churn compared to existing replication schemes, which makes ID-Replication better suited for building consistent services on top of overlays compared to other schemes. Furthermore, we show why ID-Replication is simpler to load-balance and more secure compared to successor-list replication. We evaluate our scheme in detail, and compare it with successor-list replication.
30.	Shafaat, Tallat M., et al. (author) Key-based consistency and availability in structured Overlay Networks 2008 In: Proceedings of the 17th International Symposium on High Performance Distributed Computing 2008, HPDC'08. - New York, NY, USA : ACM. - 9781595939975 ; , s. 235-236 Conference paper (peer-reviewed)abstract Structured Overlay Networks (SONs) provide a promising platform for high performance applications since they are scalable, fault-tolerant and self-managing. SONs provide lookup services that map keys to nodes that can be used as processing or storage resources. In SONs, lookups for a key may return inconsistent results. Consequently, it is difficult to provide consistent data services on top of SONs that build on key-based search. In this paper, we study the frequency of occurrence of inconsistent lookups. We show that the affect of lookup inconsistencies can be reduced by using node responsibilities. We present our results as a trade-off between consistency and availability of keys.
31.	Shafaat, Tallat M., et al. (author) Managing Network Partitions in Structured P2P Networks 2009. - 6 In: Handbook of Peer-to-Peer Networking. - : Springer. ; , s. 1127-1148 Book chapter (peer-reviewed)
32.	Shafaat, Tallat M., et al. (author) On consistency of data in structured overlay networks 2008 In: GRID COMPUTING. - NEW YORK : SPRINGER. - 9780387094564 ; , s. 249-260 Conference paper (peer-reviewed)abstract Data consistency can be violated in Distributed Hash Tables (DHTs) due to inconsistent lookups. In this paper, we identify the events leading to inconsistent lookups and inconsistent responsibilities for a key. We find the inaccuracy of failure detectors as the main reason for inconsistencies. By simulations with inaccurate failure detectors, we study the probability of reaching a system configuration which may lead to inconsistent data. We analyze majority-based algorithms for operations on replicated data. To ensure that concurrent operations do not violate consistency, they have to use non-disjoint sets of replicas. We analytically derive the probability of concurrent operations including disjoint replica sets. By combining the simulation and analytical results, we show that the probability for a violation of data consistency is negligibly low for majority-based algorithms in DHTs.
33.	Van Roy, P., et al. (author) Logic programming in the context of multiparadigm programming : the Oz experience 2003 In: Theory and Practice of Logic Programming. - 1471-0684 .- 1475-3081. ; 3, s. 717-763 Journal article (peer-reviewed)abstract Oz is a multiparadigm language that supports logic programming as one of its major paradigms. A multiparadigm language is designed to support different programming paradigms (logic, functional, constraint, object-oriented, sequential, concurrent, etc.) with equal ease. This paper has two goals: to give a tutorial of logic programming in Oz; and to show how logic programming fits naturally into the wider context of multiparadigm programming. Our experience shows that there are two classes of problems, which we call algorithmic and search problems, for which logic programming can help formulate practical solutions. Algorithmic problems have known efficient algorithms. Search problems do not have known efficient algorithms but can be solved with search. The Oz support for logic programming targets these two problem classes specifically, using the concepts needed for each. This is in contrast to the Prolog approach, which targets both classes with one set of concepts, which results in less than optimal support for each class. We give examples that can be run interactively on the Mozart system, which implements Oz, To explain the essential difference between algorithmic and search programs, we define the Oz execution model. This model subsumes both concurrent logic programming (committed-choice-style) and search-based logic programming (Prolog-style). Furthermore, as consequences of its multiparadigm nature, the model supports new abilities such as first-class top levels, deep guards, active objects, and sophisticated control of the search process. Instead of Horn clause syntax, Oz has a simple, fully compositional, higher-order syntax that accommodates the abilities of the language. We give a brief history of Oz that traces the development of its main ideas and we summarize the lessons learned from this work. Finally, we give many entry points into the Oz literature.

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