Recursos de colección

DSpace at MIT (102.107 recursos)

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MIT Open Access Articles

Mostrando recursos 101 - 120 de 28.306

  1. Single-Player and Two-Player Buttons & Scissors Games

    Burke, Kyle; Gregg, Harrison; Hearn, Robert A.; Hoffmann, Michael; Ito, Hiro; Kostitsyna, Irina; Leonard, Jody; Löffler, Maarten; Santiago, Aaron; Schmidt, Christiane; Uehara, Ryuhei; Uno, Yushi; Williams, Aaron; Demaine, Erik D; Hesterberg, Adam Classen
    We study the computational complexity of the Buttons & Scissors game and obtain sharp thresholds with respect to several parameters. Specifically we show that the game is NP-complete for C=2 colors but polytime solvable for C=1. Similarly the game is NP-complete if every color is used by at most F=4 buttons but polytime solvable for F≤3. We also consider restrictions on the board size, cut directions, and cut sizes. Finally, we introduce several natural two-player versions of the game and show that they are PSPACE-complete.

  2. Dendrimer-RNA nanoparticles generate protective immunity against lethal Ebola, H1N1 influenza, and

    Chahal, Jasdave S.; Cooper, Christopher L.; McPartlan, Justine S.; Tilley, Lucas D.; Sidik, Saima M.; Lourido, Sebastian; Bavari, Sina; Ploegh, Hidde L.; Khan, Omar Fizal; Tsosie, Jonathan; Langer, Robert S; Anderson, Daniel Griffith
    Vaccines have had broad medical impact, but existing vaccine technologies and production methods are limited in their ability to respond rapidly to evolving and emerging pathogens, or sudden outbreaks. Here, we develop a rapid-response, fully synthetic, singledose, adjuvant-free dendrimer nanoparticle vaccine platform wherein antigens are encoded by encapsulated mRNA replicons. To our knowledge, this system is the first capable of generating protective immunity against a broad spectrum of lethal pathogen challenges, including H1N1 influenza, Toxoplasma gondii, and Ebola virus. The vaccine can be formed with multiple antigenexpressing replicons, and is capable of eliciting both CD8⁺ T-cell and antibody responses. The...

  3. Efficiency at maximum power of a laser quantum heat engine enhanced by noise-induced coherence

    Dorfman, Konstantin E.; Xu, Dazhi; Cao, Jianshu
    Quantum coherence has been demonstrated in various systems including organic solar cells and solid state devices. In this article, we report the lower and upper bounds for the performance of quantum heat engines determined by the efficiency at maximum power. Our prediction based on the canonical three-level Scovil and Schulz-Dubois maser model strongly depends on the ratio of system-bath couplings for the hot and cold baths and recovers the theoretical bounds established previously for the Carnot engine. Further, introducing a fourth level to the maser model can enhance the maximal power and its efficiency, thus demonstrating the importance of quantum...

  4. Least Squares Shadowing Method for Sensitivity Analysis of Differential Equations

    Chater, Mario; Ni, Angxiu; Blonigan, Patrick Joseph; Wang, Qiqi
    For a parameterized hyperbolic system du dt = f(u; s) the derivative of the ergodic average hJi = limT→∞ 1 T R T 0 J(u(t); s) to the parameter s can be computed via the least squares shadowing (LSS) algorithm. We assume that the system is ergodic, which means that hJi depends only on s (not on the initial condition of the hyperbolic system). The algorithm solves a constrained least squares problem and, from the solution to this problem, computes the desired derivative dhJi ds . The purpose of this paper is to prove that the value given by the...

  5. Uptake Coefficients of Some Volatile Organic Compounds by Soot and Their Application in Understanding Particulate Matter Evolution in Aircraft Engine Exhaust Plumes

    Yu, Zhenhong; Liscinsky, David S.; True, Bruce; Peck, Jay; Jennings, Archer C.; Wong, Hsi-Wu; Franklin, Jonathan; Herndon, Scott C.; Waitz, Ian A.; Jun, Mina; Waitz, Ian A
    To assist microphysical modeling on particulate matter (PM) evolution emitted from aircraft engines, uptake coefficients of some volatile organic compounds on soot were experimentally determined in this study. The determined values vary from (1.0±0.1)×10⁻⁶ for water-miscible propylene glycol to (2.5±0.1)×10⁻⁵ for 2,6-dimethylnaphthalene, a polycyclic aromatic hydrocarbon. An inverse power-law correlation between uptake coefficient on soot and solubility in water was observed. Using the correlation, microphysical simulations were performed for the exhaust plume evolution from an idling aircraft, and we found that the model-predicted volatile PM composition on soot is comparable with those results from past field measurements.

  6. High-resolution and high-precision correlation of dark and light layers in the Quaternary hemipelagic sediments of the Japan Sea recovered during IODP Expedition 346

    Tada, Ryuji; Irino, Tomohisa; Ikehara, Ken; Karasuda, Akinori; Sugisaki, Saiko; Xuan, Chuang; Sagawa, Takuya; Itaki, Takuya; Kubota, Yoshimi; Lu, Song; Seki, Arisa; Murray, Richard W; Alvarez-Zarikian, Carlos; Anderson, William T; Bassetti, Maria-Angela; Brace, Bobbi J; Clemens, Steven C; da Costa Gurgel, Marcio H; Dickens, Gerald R; Dunlea, Ann G; Gallagher, Stephen J; Giosan, Liviu; Henderson, Andrew C G; Holbourn, Ann E; Lee, Gwang S; Lee, Kyung E; Lofi, Johanna; Lopes, Christina I C D; Saavedra-Pellitero, Mariem; Peterson, Larry C; Singh, Raj K; Toucanne, Samuel; Wan, Shiming; Zheng, Hongbo; Ziegler, Martin; Kinsley, Christopher William
    The Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter- to decimeter-scale alternation of dark and light clay to silty clay, which are bio-siliceous and/or bio-calcareous to a various degree. Each of the dark and light layers are considered as deposited synchronously throughout the deeper (> 500 m) part of the sea. However, attempts for correlation and age estimation of individual layers are limited to the upper few tens of meters. In addition, the exact timing of the depositional onset of these dark and light layers and its synchronicity throughout the deeper part of the sea have not been explored...

  7. Low-Flow-Coefficient Centrifugal Compressor Design for Supercritical CO₂

    Casey, M.; Spakovszky, Z.; Lettieri, Claudio; Baltadjiev, Nikola Dimitrov
    This paper presents a design strategy for very low flow coefficient multistage compressors operating with supercritical CO₂ for carbon capture and sequestration (CCS) and enhanced oil recovery (EOR). At flow coefficients less than 0.01, the stage efficiency is much reduced due to dissipation in the gas-path and more prominent leakage and windage losses. Instead of using a vaneless diffuser as is standard design practice in such applications, the current design employs a vaned diffuser to decrease the meridional velocity and to widen the gas path. The aim is to achieve a step change in performance. The impeller exit width is...

  8. Characterization of Nonequilibrium Condensation of Supercritical Carbon Dioxide in a de Laval Nozzle

    Lettieri, Claudio; Bryanston-Cross, Peter; Paxson, Derek Edwin; Spakovszky, Zoltan S
    Carbon capture and storage could significantly reduce carbon dioxide (CO₂) emissions. One of the major limitations of this technology is the energy penalty for the compression of CO₂ to supercritical conditions. To reduce the power requirements, supercritical carbon dioxide compressors must operate near saturation where phase change effects are important. Nonequilibrium condensation can occur at the leading edge of the compressor, causing performance and stability issues. The characterization of the fluid at these conditions is vital to enable advanced compressor designs at enhanced efficiency levels but the analysis is challenging due to the lack of data on metastable fluid properties....

  9. Acoel regeneration mechanisms indicate an ancient role for muscle in regenerative patterning

    Srivastava, Mansi; Salvamoser, Ranja; Raz, Amelie A.; Reddien, Peter
    Positional information is required for animal regeneration, yet how it is harbored in adult tissues is poorly understood. In planarians, positional control genes (PCGs) control regeneration outcomes and are regionally expressed predominately in the musculature. Acoels are early diverging bilaterally symmetric animals, having separated from other bilaterians > 550 million years ago. Here, we find that PCGs in the acoel Hofstenia miamia are expressed together and specifically in a primary differentiated cell type: muscle. The vast majority of Hofstenia muscle cells in regions tested express PCGs, suggesting positional information is a major feature of muscle. PCG expression domains are dynamic...

  10. Estate Tax Complexity Illustrated by the 2010 “Voluntary” Estate Tax

    Gordon, Robert; Joulfaian, David; Poterba, James Michael
    Executors of 2010 estates had an unusual choice: either to file an estate tax return and possibly pay a 35% estate tax on amounts above $5 million or instead to choose to have assets pass without an estate tax but with a carryover in basis. The data are now in, and we can see that on average, executors of 2010 estates made the right decision. Thousands did choose to voluntarily file an estate tax return, but they wound up paying little or no estate tax.

  11. Stormtime observations of the flux of plasmaspheric ions to the dayside cusp/magnetopause

    Rich, F. J.; Sandel, B. R.; Foster, John C; Coster, Anthea J; Erickson, Philip J
    [1] For the large geomagnetic disturbance on April 11, 2001, we combine data from the Millstone Hill radar, a network of GPS TEC receivers, and the DMSP F‐12 and IMAGE satellites, to estimate the sunward flux of thermal plasma associated with erosion of the outer plasmasphere/ionosphere in the dusk sector. Direct radar observations of the E×B advection of SED plasma determine a flux of >10E26 ions/s to the noontime cusp at F‐region heights. DMSP in situ observations provide a similar estimate. Assuming a dipolar magnetic field, we project our low‐altitude observations into the outer plasmasphere, obtaining a total sunward flux...

  12. Midlatitude TEC enhancements during the October 2003 superstorm

    Foster, John C; Rideout, William C
    [1] We use observations from the array of North American GPS receivers to examine the formation and severity of midlatitude enhancements and steep gradients in total electron content (TEC) during the October 30–31, 2003 superstorm. A large (∼10x) enhancement in dayside TEC was observed over the US mainland during these events as Dst decreased sharply and strong SAPS electric fields eroded the outer reaches of the post‐noon plasmasphere boundary layer (PBL) forming poleward‐streaming plumes of storm enhanced density. TEC increased to >250 TECu equatorward of the PBL. TEC gradients across the PBL over the central US exceeded 60 TECu per...

  13. Average characteristics and activity dependence of the subauroral polarization stream

    Foster, John C; Vo, H. B.
    [1] Data from the Millstone Hill incoherent scatter radar taken over two solar cycles (1979–2000) are examined to determine the average characteristics of the disturbance convection electric field in the midlatitude ionosphere. Radar azimuth scans provide a regular database of ionospheric plasma convection observations spanning auroral and subauroral latitudes, and these scans have been examined for all local times and activity conditions.We examine the occurrence and characteristics of a persistent secondary westward convection peak which lies equatorward of the auroral two‐cell convection. Individual scans and average patterns of plasma flow identify and characterize this latitudinally broad and persistent subauroral polarization...

  14. SAPS: A new categorization for sub-auroral electric fields

    Burke, W. J.; Foster, John C
    Sub‐auroral electric fields play critical roles in energizing and transporting ring current ions, as well as convecting thermal plasma in the inner magnetosphere and in the mid‐ to low‐latitude ionosphere. A number of terms have been employed to describe the sub‐auroral electric fields and many of these are specifically associated with processes established through their prior use in the literature. The continued use of descriptive terms such as penetration electric fields, polarization jets, and sub‐auroral ion drifts could lead to misunderstanding, especially when comparing the broad/narrow, persistent/transient regions of sub‐auroral electric field and plasma flow. An inclusive name for these...

  15. Higher spin six vertex model and symmetric rational functions

    Petrov, Leonid; Borodin, Alexei
    We consider a fully inhomogeneous stochastic higher spin six vertex model in a quadrant. For this model we derive concise integral representations for multi-point q-moments of the height function and for the q-correlation functions. At least in the case of the step initial condition, our formulas degenerate in appropriate limits to many known formulas of such type for integrable probabilistic systems in the (1+1)d KPZ universality class, including the stochastic six vertex model, ASEP, various q-TASEPs, and associated zero range processes. Our arguments are largely based on properties of a family of symmetric rational functions that can be defined as...

  16. 1T-TaS₂ as a quantum spin liquid

    Law, K. T.; Lee, Patrick A
    1T-TaS₂ is unique among transition metal dichalcogenides in that it is understood to be a correlation-driven insulator, where the unpaired electron in a 13-site cluster experiences enough correlation to form a Mott insulator. We argue, based on existing data, that this well-known material should be considered as a quantum spin liquid, either a fully gapped Z2 spin liquid or a Dirac spin liquid. We discuss the exotic states that emerge upon doping and propose further experimental probes. Keywords: spin liquid; Mott insulator; transition metal dichalcogenide

  17. First Results from CUORE: A Search for Lepton Number Violation via 0νββ Decay of [superscript 130]Te

    Alduino, C.; Alessandria, F.; Alfonso, K.; Andreotti, E.; Arnaboldi, C.; Avignone, F. T.; Azzolini, O.; Balata, M.; Bandac, I.; Banks, T. I.; Bari, G.; Barucci, M.; Beeman, J. W.; Bellini, F.; Benato, G.; Bersani, A.; Biare, D.; Biassoni, M.; Bragazzi, F.; Branca, A.; Brofferio, C.; Bryant, A.; Buccheri, A.; Bucci, C.; Bulfon, C.; Camacho, A.; Caminata, A.; Cao, X. G.; Capelli, S.; Capodiferro, M.; Cappelli, L.; Cardani, L.; Cariello, M.; Carniti, P.; Carrettoni, M.; Casali, N.; Cassina, L.; Cereseto, R.; Ceruti, G.; Chiarini, A.; Chiesa, D.; Chott, N.; Clemenza, M.; Conventi, D.; Copello, S.; Cosmelli, C.; Cremonesi, O.; Crescentini, C.; Creswick, R. J.; Cushman, J. S.; D’Addabbo, A.; D’Aguanno, D.; Dafinei, I.; Datskov, V.; Davis, C. J.; Del Corso, F.; Dell’Oro, S.; Deninno, M. M.; Di Domizio, S.; Di Vacri, M. L.; Di Paolo, L.; Drobizhev, A.; Ejzak, L.; Faccini, R.; Fang, D. Q.; Faverzani, M.; Ferri, E.; Ferroni, F.; Fiorini, E.; Franceschi, M. A.; Freedman, S. J.; Fujikawa, B. K.; Gaigher, R.; Giachero, A.; Gironi, L.; Giuliani, A.; Goett, J.; Gorla, P.; Gotti, C.; Guandalini, C.; Guerzoni, M.; Gutierrez, T. D.; Haller, E. E.; Han, K.; Heeger, K. M.; Hennings-Yeomans, R.; Hickerson, K. P.; Huang, H. Z.; Iannone, M.; Ioannucci, L.; Kadel, R.; Keppel, G.; Kogler, L.; Kolomensky, Yu. G.; Ligi, C.; Lim, K. E.; Liu, X.; Ma, Y. G.; Maiano, C.; Maino, M.; Marini, L.; Martinez, M.; Martinez Amaya, C.; Maruyama, R. H.; Mei, Y.; Moggi, N.; Morganti, S.; Mosteiro, P. J.; Nagorny, S. S.; Napolitano, T.; Nastasi, M.; Nisi, S.; Nones, C.; Norman, E. B.; Novati, V.; Nucciotti, A.; Nutini, I.; O’Donnell, T.; Olcese, M.; Olivieri, E.; Orio, F.; Orlandi, D.; Pagliarone, C. E.; Pallavicini, M.; Palmieri, V.; Pattavina, L.; Pavan, M.; Pedretti, M.; Pedrotta, R.; Pelosi, A.; Pessina, G.; Pettinacci, V.; Piperno, G.; Pira, C.; Pirro, S.; Pozzi, S.; Previtali, E.; Reindl, F.; Rimondi, F.; Risegari, L.; Rosenfeld, C.; Rossi, C.; Rusconi, C.; Sakai, M.; Sala, E.; Salvioni, C.; Sangiorgio, S.; Santone, D.; Schaeffer, D.; Schmidt, B.; Schmidt, J.; Scielzo, N. D.; Singh, V.; Sisti, M.; Smith, A. R.; Stivanello, F.; Taffarello, L.; Tatananni, L.; Tenconi, M.; Terranova, F.; Tessaro, M.; Tomei, C.; Ventura, G.; Vignati, M.; Wagaarachchi, S. L.; Wallig, J.; Wang, B. S.; Wang, H. W.; Welliver, B.; Wilson, J.; Wilson, K.; Wise, T.; Zanotti, L.; Zarra, C.; Zhang, G. Q.; Zhu, B. X.; Zimmermann, S.; Zucchelli, S.; Canonica, Lucia; Gladstone, Laura; Hansen, E. V.; Leder, Alexander Friedrich; Ouellet, Jonathan L; Winslow, Lindley
    The CUORE experiment, a ton-scale cryogenic bolometer array, recently began operation at the Laboratori Nazionali del Gran Sasso in Italy. The array represents a significant advancement in this technology, and in this work we apply it for the first time to a high-sensitivity search for a lepton-number-violating process: [superscript 130]Te neutrinoless double-beta decay. Examining a total TeO[subscript 2] exposure of 86.3 kg yr, characterized by an effective energy resolution of (7.7±0.5)  keV FWHM and a background in the region of interest of (0.014±0.002)  counts/(keV kg yr), we find no evidence for neutrinoless double-beta decay. Including systematic uncertainties, we place a lower limit on the decay half-life...

  18. Attention and anticipation in fast visual-inertial navigation

    Carlone, Luca; Karaman, Sertac
    Visual attention is the cognitive process that allows humans to parse a large amount of sensory data by selecting relevant information and filtering out irrelevant stimuli. This papers develops a computational approach for visual attention in robots. We consider a Visual-Inertial Navigation (VIN) problem in which a robot needs to estimate its state using an on-board camera and an inertial sensor. The robot can allocate limited resources to VIN, due to time and energy constraints. Therefore, we answer the following question: under limited resources, what are the most relevant visual cues to maximize the performance of visual-inertial navigation? Our approach...

  19. Capacity and delay scaling for broadcast transmission in highly mobile wireless networks

    Talak, Rajat Rajendra; Karaman, Sertac; Modiano, Eytan H
    We study broadcast capacity and minimum delay scaling laws for highly mobile wireless networks, in which each node has to disseminate or broadcast packets to all other nodes in the network. In particular, we consider a cell partitioned network under the simplified independent and identically distributed (IID) mobility model, in which each node chooses a new cell at random every time slot. We derive scaling laws for broadcast capacity and minimum delay as a function of the cell size. We propose a simple first-come-first-serve (FCFS) flooding scheme that nearly achieves both capacity and minimum delay scaling. Our results show that...

  20. Local Oxidation Nanolithography on Metallic Transition Metal Dichalcogenides Surfaces

    Pinilla-Cienfuegos, Elena; Mañas-Valero, Samuel; Tatay, Sergio; Forment-Aliaga, Alicia; Coronado, Eugenio; Navarro Moratalla, Efren Adolfo
    The integration of atomically-thin layers of two dimensional (2D) materials in nanodevices demands for precise techniques at the nanoscale permitting their local modification, structuration or resettlement. Here, we present the use of Local Oxidation Nanolithography (LON) performed with an Atomic Force Microscope (AFM) for the patterning of nanometric motifs on different metallic Transition Metal Dichalcogenides (TMDCs). We show the results of a systematic study of the parameters that affect the LON process as well as the use of two different modes of lithographic operation: dynamic and static. The application of this kind of lithography in different types of TMDCs demonstrates...

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