68 research outputs found
Parallel Algorithm Scalability Issues in PetaFLOPS Architectures
No full textThe projected design space of petaFLOPS architectures entails exploitationof very large degrees of concurrency, locality of data access, and toleranceto latency. This puts considerable pressure on the design of parallelalgorithms capable of effectively utilizing increasing amounts of processingresources in a memory and bandwidth constrained environment. This aspect ofalgorithm design, also referred to as scalability analysis, is a keycomponent for guiding algorithm designers as well as hardware architects.By identifying bottlenecks to scalability and machine parameters thatinfluence these bottlenecks, scalability analysis provides insights toalleviating the bottlenecks in the context of the specific algorithm.In this paper, we motivate the need for, and benefits of scalabilityanalysis in the context of petaFLOPS systems. We overview variousscalability metrics and study their suitability to petaFLOPS system.We also present sample analysis of selected computational kernels fromdense linear algebra, fast fourier transforms, and data intensive applications(association rule mining). The objective of this analysis is to demonstratethe analysis framework and its use in identifying desirable architecturalfeatures as well the ability of these selected kernels to scale to petaFLOPSsystems.Garma, Ananth; Gupta, Anshul; Han, Euihong; Kumar, Vipin. (2001). Parallel Algorithm Scalability Issues in PetaFLOPS Architectures. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/215488
Mimicking the nuclear pore complex using nanopores
No full textNuclear pore complexes acts as a gatekeeper for molecular transport between the nucleus and the cytoplasm in eukaryotic cells. The central NPC channel is filled with intrinsically disordered FG domains (phenylalanine (F), glycine (G)) that are responsible for the fascinating selectivity of NPCs, for which the underlying mechanism is still under considerable debate. In this thesis, a minimalistic mimic of (NPCs) was constructed using solid-state nanopore and DNA origami to study the spatial arrangement and transport process.BN/Cees Dekker La
Study of DNA origami plates on graphene nanopores
No full textCombining DNA origami with solid-state nanopores has been gaining an increasing amount of attention due to its potential for biosensing applications. Accordingly, origami plate dockings onto conventional solid-state silicon nitride pores with membranes of ?20nm thick were previously studied. Here, we examine whether graphene, with its single layer of carbon atoms, poses advantages over silicon-nitride pores. The conductance blockades due to origami plate dockings were characterized as a function of salt concentration and applied bias voltage and compared to the silicon-nitride data. As expected, it was found that conductance blockades increase with salt concentration and voltage. The relative conductance drop in graphene was however found to be similar to that for silicon nitride pores, whereas theory predicts that the blockade signal is larger in graphene pores. We have further compared the root-mean-squared noise levels of the ionic current through hybrid graphene-origami pores and bare pores, and found that the noise in the hybrid pores was slightly higher than in the bare pore current. Finally, it was tested whether the plates stick to the graphene pore in presence of EDTA. This was done by docking the plates and subjecting them to a negative ramping voltage. Without EDTA, no evidence of sticking was found, whereas with EDTA, 88.2\% of docked plates appeared to be sticking.Technische NatuurkundeBionanoscienceApplied Science
Electrical and optical detection of streamers in transformer insulation
No full textThe use of esters as transformer insulation has been gaining increasing interest over the past few years because of their better environmental performance, higher resistance to the influence of moisture and for some particular liquids, higher flash point as well. However, in order to completely replace the traditional mineral oil and be considered as a viable insulating fluid for high voltage equipments, these liquids must have comparable responses to mineral oil under DC,AC, lightning impulse as well as switching impulse waveforms. The study of pre-breakdown phenomenon(streamer activity) under different stresses has proven to be crucial in determining the breakdown process taking place in transformer insulations. To study the streamer characteristics in ester (MIDEL 7131) and mineral oil (Shell Diala Transformer oil), both electrical and optical techniques have been used in this thesis. Significant research was conducted in identifying the parameters for the selection of the optical sensor suitable for this application. Various diagnostic techniques were employed for accurate detection of streamers electrically as well as optically. Streamers were initially studied in the highly non uniform needle-plane geometry under DC and lightning impulse stress. This configuration represents the situation of a defect in the transformer. Pressboard was introduced at the needle tip to simulate the effect of triple point as a source of discharge. Experiments conducted in Lodz University of Technology proved to be crucial in understanding the optical detection of streamers under this configuration. The main goal of this thesis was to detect streamers originating from transformer winding. For the first time, electrode arrangements involving transformer windings were tested in ester and mineral oil under lightning impulse for streamer activity. The thesis presents the various streamer signals obtained under different configurations and provides important analysis regarding the characteristics of streamers in transformer insulation. The possible effect of spacers between transformer windings and wooden blocks used in transformer coils in also analyzed. The tests performed in this thesis can contribute to the ultimate goal of understanding the difference in streamer propagation in real life electrode arrangements between ester and mineral oil.Electrical Engineerin
Aetiology and management options for secondary referred otalgia: a systematic review and meta-analyses
No full textObjectives of review: To review the literature for the evidence base for the aetiology and management of referred otalgia, looking particularly at non-malignant, neuralgic, structural and functional issues.
Type of review: Systematic review.
Search strategy: A systematic literature search was undertaken from the databases of EMBASE, CINAHL, MEDLINE®, BNI, and Cochrane Library according to predefined inclusion and exclusion criteria.
Evaluation method: All relevant titles, abstracts and full text articles were reviewed by three authors who resolved any differences by discussion and consultation with senior author.
Results: 44 articles were included in our review. The overall quality of evidence was low, with the vast majority of the studies being case-series with three cohort and four randomised-controlled trials included. The prime causes and management strategies were focussed on temporomandibular joint dysfunction (TMJD), Eagle syndrome and neuralgia. Our meta-analyses found no difference on the management strategies for the interventions found.
Conclusions: Referred otalgia is common and treatment should be aimed at the underlying pathology. Potential aetiologies are vast given the extensive sensory innervation of the ear. An understanding of this and a structured approach to patient assessment is important for optimal patient management
Comparison of SPIHT and Lifting Scheme Image Compression Techniques for Satellite Imageries
No full textBiomimetic Nanopores with Yeast Nucleoporins
No full textNuclear pore complexes (NPC’s) facilitate the exchange of macromolecules between the cytoplasm and nucleus and act as a selective barrier for macromolecules in eukaryotes. Ongoing research suggests that the discriminatory function of the NPC is caused by nucleoporins rich in phenylalanine-glycine amino acids residue repeats (FG-regions) which fill the nuclear pore. To determine if the FG-domains are responsible for the selectivity of a NPC, in this research we will mimic a nuclear pore complex by coating a solid state nanopore with yeast FG-nup-NSP1. After coating a wild-type nucleoporin, to a solid-state nanopore, we find that a yeast importer protein kap95 was able to translocate through the nanopore. The dwell times were on the order of tens of milliseconds. An artificial control protein, tCherry, with the same size as kap95, was not able to pass the artificial NPC. Bycoating a solid-state nanopore with mutated FG-nup-NSP1, where hydrophobic amino acid residues (F, I, L and V) were replaced with serine, we found that kap95 translocated with much lower translocation times, comparable to an uncoated nanopore, indicating less interaction with the mutated nucleoporins. Furthermore tCherry was also able to pass through the mimicked nuclear pore with mutated nucleoporins, making a very strong argument that FG-repeat regions in nucleoporins are responsible for the selectivity in NPC’s.Applied Physic
Atomistic modeling and simulations of 2D materials : chemical vapor deposition, nanoporous defects, force-field development, wetting, and friction
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references.Two-dimensional (2D) materials, such as, graphene, transition metal dichalcogenides (TMDs) (e.g., molybdenum disulfide (MoS₂)), and hexagonal boron nitride (hBN), have recently received considerable attention, due to their layer-number-dependent optoelectronic, mechanical, and barrier properties. However, physical understanding of the controlled synthesis and interfacial behavior of 2D materials is still lacking. In this thesis: First, I construct a generalized mechanistic model for the growth of TMD monolayers using chemical vapor deposition (CVD). Combining kinetic Monte Carlo (KMC) simulations and a chemical engineering transport model, I am able to predict the experimentally-observed shape and size evolution of the MoS₂ morphology inside a CVD reactor. Second, I address the challenge of solving the Isomer Cataloging Problem (ICP) for lattice nanopores in 2D materials.Combining electronic structure density functional theory (DFT) calculations, KMC simulations, and chemical graph theory, I generate a catalog of unique, most-probable isomers of 2D lattice nanopores, demonstrating remarkable agreement with experimental microscopy data for nanopores in graphene and hBN. Third, I study the photoluminescent properties of nanoporous defects in hBN by combining my solution to the ICP with extensive hybrid DFT calculations of electronic bandgaps. Doing so, I map the experimentally-observed emission energies to one or more defect shapes in hBN, thereby demonstrating structure-property relationships for defects in hBN, with implications for single-photon emission from hBN devices. Fourth, using molecular dynamics (MD) simulations, I show that electrostatic interactions play a negligible role in determining the contact angle and the friction coefficient of water on the MoS₂ basal plane.I show that other planes (e.g., the zigzag plane) are polar with respect to interactions with water, thereby illustrating the role of edge effects in MoS₂. Fifth, I combine lattice dynamics calculations with DFT-based MD simulations to develop a force field for hBN for use in mechanical and interfacial applications. The force field predicts the crystal structure, elastic constants, and phonon dispersion relation of hBN with good accuracy, and demonstrates remarkable agreement with the interlayer and water-hBN binding energies predicted by advanced ab initio calculations. Finally, using MD simulations, I study the wetting and frictional properties of hBN by three different liquids of varying degrees of polarity. I infer that electrostatic interactions affect the frictional properties of various liquids in contact with hBN to different extents, and propose the mean-squared total lateral force as a physical metric to rationalize this observation.This finding implies that liquids with lower wettability can exhibit higher friction on hBN surfaces. In conclusion, the theoretical and simulation methods developed and applied in this thesis should inform the synthesis of 2D materials, and their use in various applications, such as, optoelectronic devices, mechanical composites, and membranes for gas separation and water desalination.by Ananth Govind Rajan.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineerin
Yang-Mills theories and quadratic forms
No full textAbstract: We show that the Hamiltonian of (N=1, d = 10) super Yang-Mills can be expressed as a quadratic form in a very similar manner to that of the (N=4, d = 4) theory. We find a similar quadratic form structure for pure Yang-Mills theory but this feature, in the non-supersymmetric case, seems to be unique to four dimensions. We discuss some consequences of this feature. © 2015, The Author(s)
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