691 research outputs found
Systems Methodology and Framework for Problem Definition in Mobile Ad Hoc Networks
Mobile Ad Hoc Networks are communication networks built up of a collection of mobile devices which can communicate through wireless connections. Mobile Ad Hoc Networks have many challenges such as routing, which is the task of directing data packets from a source node to a given destination. This task is particularly hard in Mobile Ad Hoc Networks: due to the mobility of the network elements and the lack of central control, robustness and adaptability in routing algorithms and work in a decentralized and self organizing way. Through the principles of systems architecting and Engineering; the problem statement in Mobile Ad Hoc Networks could be defined more specifically and accurately. The uncertainties and techniques for mitigating and even taking positive advantages of them can be achieved through a framework of uncertainties as in [1]. The systems methodology framework called Total Systems Intervention (TSI) described by Flood and Jackson [2] select a systems methodology for Mobile Ad Hoc Networks. The purpose of this paper is to show how TSI when integrated with a framework created to understand the risks and opportunities can help develop strategies to minimize the risks and to take advantage of the opportunities for facing challenges in Mobile Ad Hoc Networks
Recommender Systems with Generative Retrieval
Modern recommender systems perform large-scale retrieval by first embedding
queries and item candidates in the same unified space, followed by approximate
nearest neighbor search to select top candidates given a query embedding. In
this paper, we propose a novel generative retrieval approach, where the
retrieval model autoregressively decodes the identifiers of the target
candidates. To that end, we create semantically meaningful tuple of codewords
to serve as a Semantic ID for each item. Given Semantic IDs for items in a user
session, a Transformer-based sequence-to-sequence model is trained to predict
the Semantic ID of the next item that the user will interact with. To the best
of our knowledge, this is the first Semantic ID-based generative model for
recommendation tasks. We show that recommender systems trained with the
proposed paradigm significantly outperform the current SOTA models on various
datasets. In addition, we show that incorporating Semantic IDs into the
sequence-to-sequence model enhances its ability to generalize, as evidenced by
the improved retrieval performance observed for items with no prior interaction
history.Comment: Preprint versio
Predictive runtime code scheduling for heterogeneous architectures
Heterogeneous architectures are currently widespread. With
the advent of easy-to-program general purpose GPUs, virtually every re-
cent desktop computer is a heterogeneous system. Combining the CPU
and the GPU brings great amounts of processing power. However, such
architectures are often used in a restricted way for domain-speci c appli-
cations like scienti c applications and games, and they tend to be used
by a single application at a time. We envision future heterogeneous com-
puting systems where all their heterogeneous resources are continuously
utilized by di erent applications with versioned critical parts to be able
to better adapt their behavior and improve execution time, power con-
sumption, response time and other constraints at runtime. Under such a
model, adaptive scheduling becomes a critical component.
In this paper, we propose a novel predictive user-level scheduler based on
past performance history for heterogeneous systems. We developed sev-
eral scheduling policies and present the study of their impact on system
performance. We demonstrate that such scheduler allows multiple appli-
cations to fully utilize all available processing resources in CPU/GPU-
like systems and consistently achieve speedups ranging from 30% to 40%
compared to just using the GPU in a single application mode.Postprint (published version
A Magnetically Torqued Disk Model for Be Stars
Despite extensive study, the mechanisms by which Be star disks acquire high
densities and angular momentum while displaying variability on many time scales
are still far from clear. In this paper, we discuss how magnetic torquing may
help explain disk formation with the observed quasi-Keplerian (as opposed to
expanding) velocity structure and their variability. We focus on the effects of
the rapid rotation of Be stars, considering the regime where centrifugal forces
provide the dominant radial support of the disk material. Using a kinematic
description of the angular velocity, vphi(r), in the disk and a parametric
model of an aligned field with a strength B(r) we develop analytic expressions
for the disk properties that allow us to estimate the stellar surface field
strength necessary to create such a disk for a range of stars on the
main-sequence. The model explains why disks are most common for main-sequence
stars at about spectral class B2 V. The earlier type stars with very fast and
high density winds would require unacceptably strong surface fields (> 10^3
Gauss) to form torqued disks, while the late B stars (with their low mass loss
rates) tend to form disks that produce only small fluxes in the dominant Be
diagnostics. For stars at B2 V the average surface field required is about 300
Gauss. The predicted disks provide an intrinsic polarization and a flux at
Halpha comparable to observations. We also discuss whether the effect on field
containment of the time dependent accumulation of matter in the flux tubes/disk
can help explain some of the observed variability of Be star disks.Comment: ApJ, in press. 46 pages, 12 figure
Tuberculosis diagnosis cascade in Blantyre, Malawi : a prospective cohort study
Wellcome Trust. PM is funded by Wellcome (206575/Z/17/Z). ELC is funded by Wellcome (200901/Z/16/Z). ELW received salary funding from the UK Medical Research Council (grant number MR/K012126/1), this award is jointly funded by the UK Medical Research Council (MRC) and the UK Department for International Development (DFID) under the MRC/DFID Concordat agreement and is also part of the EDCTP2 programme supported by the European Union.Background Tuberculosis (TB) control relies on early diagnosis and treatment. International guidelines recommend systematic TB screening at health facilities, but implementation is challenging. We investigated completion of recommended TB screening steps in Blantyre, Malawi. Methods A prospective cohort recruited adult outpatients attending Bangwe primary clinic. Entry interviews were linked to exit interviews. The proportion of participants progressing through each step of the diagnostic pathway were estimated. Factors associated with request for sputum were investigated using multivariable logistic regression. Results Of 5442 clinic attendances 2397 (44%) had exit interviews. In clinically indicated participants (n = 445) 256 (57.5%) were asked about cough, 36 (8.1%) were asked for sputum, 21 (4.7%) gave sputum and 1 (0.2%) received same-day results. Significant associations with request for sputum were: any TB symptom (aOR:3.20, 95%CI:2.02–5.06), increasing age (aOR:1.02, 95%CI:1.01–1.04 per year) and for HIV-negative participants only, a history of previous TB (aOR:3.37, 95%CI:1.45–7.81). Numbers requiring sputum tests (26/day) outnumbered diagnostic capacity (8–12/day). Conclusions Patients were lost at every stage of the TB care cascade, with same day sputum submission following all steps of the diagnosis cascade achieved in only 4.7% if clinically indicated. Infection control strategies should be implemented, with reporting on early steps of the TB care cascade formalised. High-throughput screening interventions, such as digital CXR, that can achieve same-day TB diagnosis are urgently needed to meet WHO End TB goals.Peer reviewe
Uptake of home-based voluntary HIV testing in sub-Saharan Africa: a systematic review and meta-analysis
Improving access to HIV testing is a key priority in scaling up HIV treatment and prevention services. Home-based voluntary counselling and testing (HBT) as an approach to delivering wide-scale HIV testing is explored here
Meta-heuristically seeded genetic algorithm for independent job scheduling in grid computing
Grid computing is an infrastructure which connects geographically distributed computers owned by various organizations allowing their resources, such as computational power and storage capabilities, to be shared, selected, and aggregated. Job scheduling problem is one of the most difficult tasks in grid computing systems. To solve this problem efficiently, new methods are required. In this paper, a seeded genetic algorithm is proposed which uses a meta-heuristic algorithm to generate its initial population. To evaluate the performance of the proposed method in terms of minimizing the makespan, the Expected Time to Compute (ETC) simulation model is used to carry out a number of experiments. The results show that the proposed algorithm performs better than other selected techniques
Pericentromeric satellite repeat expansions through RNA-derived DNA intermediates in cancer
Aberrant transcription of the pericentromeric human satellite II (HSATII) repeat is present in a wide variety of epithelial cancers. In deriving experimental systems to study its deregulation, we observed that HSATII expression is induced in colon cancer cells cultured as xenografts or under nonadherent conditions in vitro, but it is rapidly lost in standard 2D cultures. Unexpectedly, physiological induction of endogenous HSATII RNA, as well as introduction of synthetic HSATII transcripts, generated cDNA intermediates in the form of DNA/RNA hybrids. Single molecule sequencing of tumor xenografts showed that HSATII RNA-derived DNA (rdDNA) molecules are stably incorporated within pericentromeric loci. Suppression of RT activity using small molecule inhibitors reduced HSATII copy gain. Analysis of whole-genome sequencing data revealed that HSATII copy number gain is a common feature in primary human colon tumors and is associated with a lower overall survival. Together, our observations suggest that cancer-associated derepression of specific repetitive sequences can promote their RNA-driven genomic expansion, with potential implications on pericentromeric architecture
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