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MIT Open Access Articles

Mostrando recursos 41 - 60 de 26.537

  1. Reduced self-referential neural response during intergroup competition predicts competitor harm

    Cikara, M.; Jenkins, A.C.; Dufour, Nicholas Paul; Saxe, Rebecca R
    Why do interactions become more hostile when social relations shift from "me versus you" to "us versus them"? One possibility is that acting with a group can reduce spontaneous self-referential processing in the moral domain and, in turn, facilitate competitor harm. We tested this hypothesis in an fMRI experiment in which (i) participants performed a competitive task once alone and once with a group; (ii) spontaneous self-referential processing during competition was indexed unobtrusively by activation in an independently localized region of the medial prefrontal cortex (mPFC) associated with self-reference; and (iii) we assessed participants' willingness to harm competitors versus teammates....

  2. Their pain gives us pleasure: How intergroup dynamics shape empathic failures and counter-empathic responses

    Cikara, M.; Van Bavel, J.J.; Bruneau, Emile Gabriel; Saxe, Rebecca R
    Despite its early origins and adaptive functions, empathy is not inevitable; people routinely fail to empathize with others, especially members of different social or cultural groups. In five experiments, we systematically explore how social identity, functional relations between groups, competitive threat, and perceived entitativity contribute to intergroup empathy bias: the tendency not only to empathize less with out-group relative to in-group members, but also to feel pleasure in response to their pain (and pain in response to their pleasure). When teams are set in direct competition, affective responses to competition-irrelevant events are characterized not only by less empathy toward out-group...

  3. Convex learning of multiple tasks and their structure

    Ciliberto, Carlo; Mroueh, Youssef; Poggio, Tomaso A; Rosasco, Lorenzo
    Reducing the amount of human supervision is a key problem in machine learning and a natural approach is that of exploiting the relations (structure) among different tasks. This is the idea at the core of multi-task learning. In this context a fundamental question is how to incorporate the tasks structure in the learning problem. We tackle this question by studying a general computational framework that allows to encode a-priori knowledge of the tasks structure in the form of a convex penalty; in this setting a variety of previously proposed methods can be recovered as special cases, including linear and non-linear...

  4. Learning with a Wasserstein loss

    Araya-Polo, Mauricio; Frogner, Charles Albert; Zhang, Chiyuan; Mobahi, Hossein; Poggio, Tomaso A
    Learning to predict multi-label outputs is challenging, but in many problems there is a natural metric on the outputs that can be used to improve predictions.In this paper we develop a loss function for multi-label learning, based on the Wasserstein distance. The Wasserstein distance provides a natural notion of dissimilarity for probability measures. Although optimizing with respect to the exact Wasserstein distance is costly, recent work has described a regularized approximation that is efficiently computed. We describe an efficient learning algorithm based on this regularization, as well as a novel extension of the Wasserstein distance from probability measures to unnormalized...

  5. Learning with group invariant features: A Kernel perspective

    Mroueh, Youssef; Poggio, Tomaso A; Voinea, Stephen Constantin
    We analyze in this paper a random feature map based on a theory of invariance (I-theory) introduced in [1]. More specifically, a group invariant signal signature is obtained through cumulative distributions of group-transformed random projections. Our analysis bridges invariant feature learning with kernel methods, as we show that this feature map defines an expected Haar-integration kernel that is invariant to the specified group action. We show how this non-linear random feature map approximates this group invariant kernel uniformly on a set of N points. Moreover, we show that it defines a function space that is dense in the equivalent Invariant...

  6. How important is weight symmetry in backpropagation?

    Liao, Qianli; Leibo, Joel Z; Poggio, Tomaso A
    Gradient backpropagation (BP) requires symmetric feedforward and feedback connections-the same weights must be used for forward and backward passes. This "weight transport problem" (Grossberg 1987) is thought to be one of the main reasons to doubt BP's biologically plausibility. Using 15 different classification datasets, we systematically investigate to what extent BP really depends on weight symmetry. In a study that turned out to be surprisingly similar in spirit to Lillicrap et al.'s demonstration (Lillicrap et al. 2014) but orthogonal in its results, our experiments indicate that: (1) the magnitudes of feedback weights do not matter to performance (2) the signs...

  7. The TWA 3 Young Triple System: Orbits, Disks, Evolution

    Kellogg, Kendra; Prato, L.; Torres, Guillermo; Schaefer, G. H.; Avilez, I.; Ruíz-Rodríguez, D.; Wasserman, L. H.; Bonanos, Alceste Z.; Guenther, E. W.; Neuhäuser, R.; Morzinski, Katie M.; Close, Laird; Bailey, Vanessa; Hinz, Phil; Males, Jared R.; Levine, Stephen E.; Bosh, Amanda S.
    We have characterized the spectroscopic orbit of the TWA 3A binary and provide preliminary families of probable solutions for the TWA 3A visual orbit, as well as for the wide TWA 3A-B orbit. TWA 3 is a hierarchical triple located at 34 pc in the ∼10 Myr old TW Hya association. The wide component separation is 1.″55; the close pair was first identified as a possible binary almost 20 years ago. We initially identified the 35-day period orbital solution using high-resolution infrared spectroscopy that angularly resolved the A and B components. We then refined the preliminary orbit by combining the...

  8. RAVE J203843.2–002333: The First Highly R-process-enhanced Star Identified in the RAVE Survey

    Placco, Vinicius M.; Holmbeck, Erika M.; Beers, Timothy C.; Surman, Rebecca A.; Points, Sean D.; Kaleida, Catherine C.; Hansen, Terese T.; Sakari, Charli M.; Casey, Andrew R.; Frebel, Anna L.; Ji, Alexander Pung; Ezzeddine, Rana
    We report the discovery of RAVE J203843.2-002333, a bright (V = 12.73), very metal-poor ([Fe/H] = -2.91), r-process-enhanced ([Ba/Eu] = +1.64 and = -0.81) star selected from the RAVE survey. This star was identified as a metal-poor candidate based on its medium-resolution (R ∼ 1600) spectrum obtained with the KPNO/Mayall Telescope, and followed up with high-resolution (R ∼ 66,000) spectroscopy with the Magellan/Clay Telescope, allowing for the determination of elemental abundances for 24 neutron-capture elements, including thorium and uranium. RAVE J2038-0023 is only the fourth metal-poor star with a clearly measured U abundance. The derived chemical abundance pattern exhibits good...

  9. iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

    Pasham, Dheeraj Ranga Reddy
    We present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute mag M[subscript g] = -17.2. The maximum bolometric luminosity (from optical and UV) was L[subscript p] ≃ (1.0 ± 0.15) × 10[superscript 43] erg s[superscript -1], an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with L ∝ e [superscript -(t-t0)/τ], where t[subscript 0] = 57631.0 (MJD)...

  10. Study of Jet Quenching with Z + jet Correlations in Pb-Pb and pp Collisions at √s[subscript NN] = 5.02 TeV

    Abercrombie, Daniel Robert; Allen, Brandon Leigh; Apyan, Aram; Azzolini, Virginia; Barbieri, Richard Alexander; Baty, Austin Alan; Bi, Ran; Bierwagen, Katharina; Brandt, Stephanie Akemi; Busza, Wit; Cali, Ivan Amos; D'Alfonso, Mariarosaria; Demiragli, Zeynep; Di Matteo, Leonardo; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Hsu, Dylan George; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Krajczar, Krisztian F.; Lai, Yue Shi; Lee, Yen-Jie; Levin, Amy Elizabeth; Luckey Jr, P David; Maier, Benedikt; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Siddharth Madhavan; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Tatar, Kaya; Varma, Mukund Madhav; Velicanu, Dragos Alexandru; Wang, J.; Wang, Ta-Wei; Wyslouch, Boleslaw; Yang, Mingming
    The production of jets in association with Z bosons, reconstructed via the μ[superscript +]μ[superscript -] and e[superscript +]e[superscript -] decay channels, is studied in pp and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The Pb-Pb collisions were analyzed in the 0%-30% centrality range. The back-to-back azimuthal alignment was studied in both pp and Pb-Pb collisions for Z bosons with transverse momentum p[superscript Z][subscript T] > 60 GeV/c and a recoiling jet with p[superscript jet][subscript T] > 30 GeV/c. The p[subscript...

  11. Search for supersymmetry in multijet events with missing transverse momentum in proton-proton collisions at 13 TeV

    Abercrombie, Daniel Robert; Allen, Brandon Leigh; Azzolini, Virginia; Barbieri, Richard Alexander; Baty, Austin Alan; Bi, Ran; Brandt, Stephanie Akemi; Busza, Wit; Cali, Ivan Amos; D'Alfonso, Mariarosaria; Demiragli, Zeynep; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Hsu, Dylan George; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Lai, Yue Shi; Lee, Yen-Jie; Levin, Andrew Michael; Luckey Jr, P David; Maier, Benedikt; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Siddharth Madhavan; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Tatar, Kaya; Velicanu, Dragos Alexandru; Wang, Ta-Wei; Wyslouch, Boleslaw
    A search for supersymmetry is presented based on multijet events with large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of √s=13 TeV. The data, corresponding to an integrated luminosity of 35.9 fb[superscript −1], were collected with the CMS detector at the CERN LHC in 2016. The analysis utilizes four-dimensional exclusive search regions defined in terms of the number of jets, the number of tagged bottom quark jets, the scalar sum of jet transverse momenta, and the magnitude of the vector sum of jet transverse momenta. No evidence for a significant excess of events is observed relative...

  12. Measurement of the B± Meson Nuclear Modification Factor in Pb-Pb Collisions at √s[subscript NN] =5.02  TeV

    CMS Collaboration; Abercrombie, Daniel Robert; Allen, Brandon Leigh; Azzolini, Virginia; Barbieri, Richard Alexander; Baty, Austin Alan; Bi, Ran; Bierwagen, Katharina; Brandt, Stephanie Akemi; Busza, Wit; Cali, Ivan Amos; D'Alfonso, Mariarosaria; Demiragli, Zeynep; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Hsu, Dylan George; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Lai, Yue Shi; Lee, Yen-Jie; Levin, Andrew Michael; Luckey Jr, P David; Maier, Benedikt; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Sruthi A.; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Tatar, Kaya; Turner, Andrew Patrick; Velicanu, Dragos Alexandru; Wang, Jing; Wang, Ta-Wei; Wyslouch, Boleslaw
    Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. The differential production cross sections of B± mesons are measured via the exclusive decay channels B±→J/ψK±→μ+μ-K± as a function of transverse momentum in pp and Pb-Pb collisions at a center-of-mass energy sNN=5.02 TeV per nucleon pair with the CMS detector at the LHC. The pp(Pb-Pb) data set used for this analysis corresponds to an integrated luminosity of 28.0 pb-1 (351 μb-1). The measurement is performed in the B± meson transverse momentum range of 7 to 50 GeV/c, in the rapidity...

  13. Search for Supersymmetry in pp Collisions at √s = 13  TeV in the Single-Lepton Final State Using the Sum of Masses of Large-Radius Jets

    CMS Collaboration; Abercrombie, Daniel Robert; Allen, Brandon Leigh; Azzolini, Virginia; Barbieri, Richard Alexander; Baty, Austin Alan; Bi, R.; Brandt, Stephanie Akemi; Busza, Wit; Cali, Ivan Amos; D'Alfonso, Mariarosaria; Demiragli, Zeynep; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Hsu, Dylan George; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Lai, Yue Shi; Lee, Yen-Jie; Levin, Andrew Michael; Luckey Jr, P David; Maier, Benedikt; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Siddharth Madhavan; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Tatar, Kaya; Velicanu, Dragos Alexandru; Wang, Jing; Wang, Ta-Wei; Wyslouch, Boleslaw
    Results are reported from a search for supersymmetric particles in proton-proton collisions in the final state with a single lepton, multiple jets, including at least one b-tagged jet, and large missing transverse momentum. The search uses a sample of proton-proton collision data at s=13 TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb⁻¹. The observed event yields in the signal regions are consistent with those expected from standard model backgrounds. The results are interpreted in the context of simplified models of supersymmetry involving gluino pair production, with gluino decay into either on-...

  14. Into the fourth dimension

    Des Marais, David Lee
    The influence of time on the drought response of Brassica rapa, an agriculturally important species of plant, has been clarified.

  15. NPTFit: A Code for Non-Poissonian Template Fitting

    Mishra-Sharma, Siddharth; Rodd, Nicholas Llewellyn; Safdi, Benjamin Ryan
    We present NPTFit, an open-source code package, written in Python and Cython, for performing non-Poissonian template fits (NPTFs). The NPTF is a recently developed statistical procedure for characterizing the contribution of unresolved point sources (PSs) to astrophysical data sets. The NPTF was first applied to Fermi gamma-ray data to provide evidence that the excess of ∼GeV gamma-rays observed in the inner regions of the Milky Way likely arises from a population of sub-threshold point sources, and the NPTF has since found additional applications studying sub-threshold extragalactic sources at high Galactic latitudes. The NPTF generalizes traditional astrophysical template fits to allow...

  16. Condition numbers of indefinite rank 2 ghost Wishart matrices

    Movassagh, Ramis; Edelman, Alan
    Abstract We define an indefinite Wishart matrix as a matrix of the form A= W[superscript T]WΣ, where Σ is an indefinite diagonal matrix and W is a matrix of independent standard normals. We focus on the case where W is L×2 which has engineering applications. We obtain the distribution of the ratio of the eigenvalues of A. This distribution can be "folded" to give the distribution of the condition number. We calculate formulas for W real (β=1), complex (β=2), quaternionic (β=4) or any ghost 0 < β < ∞. We then corroborate our work by comparing them against numerical experiments.

  17. Heteroepitaxial growth of In In[subscript 0.30]Ga[subscript 0.70]As high-electron mobility transistor on 200 mm silicon substrate using metamorphic graded buffer

    Kohen, David; Nguyen, Xuan Sang; Yadav, Sachin; Kumar, Annie; Made, Riko I; Gong, Xiao; Lee, Kwang Hong; Lee, Kenneth Eng Kian; Yeo, Yee Chia; Yoon, Soon Fatt; Fitzgerald, Eugene A.; Heidelberger, Christopher
    We report on the growth of an In[subscript 0.30]Ga[subscript 0.70]As channel high-electron mobility transistor (HEMT) on a 200 mm silicon wafer by metal organic vapor phase epitaxy. By using a 3 μm thick buffer comprising a Ge layer, a GaAs layer and an InAlAs compositionally graded strain relaxing buffer, we achieve threading dislocation density of (1.0 ± 0.3) × 10[superscript 7]cm[subscript -2] with a surface roughness of 10 nm RMS. No phase separation was observed during the InAlAs compositionally graded buffer layer growth. 1.4 μm long channel length transistors are fabricated from the wafer with I[subscript DS] of 70 μA/μm...

  18. Ten-month-old infants infer the value of goals from the costs of actions

    Liu, Shari; Spelke, Elizabeth S.; Ullman, Tomer David; Tenenbaum, Joshua B
    Infants understand that people pursue goals, but how do they learn which goals people prefer? We tested whether infants solve this problem by inverting a mental model of action planning, trading off the costs of acting against the rewards actions bring. After seeing an agent attain two goals equally often at varying costs, infants expected the agent to prefer the goal it attained through costlier actions. These expectations held across three experiments that conveyed cost through different physical path features (height, width, and incline angle), suggesting that an abstract variable—such as “force,” “work,” or “effort”—supported infants’ inferences. We modeled infants’...

  19. BLISS is a versatile and quantitative method for genome-wide profiling of DNA double-strand breaks

    Mirzazadeh, Reza; Garnerone, Silvano; Schneider, Martin W.; Kallas, Tomasz; Custodio, Joaquin; Wernersson, Erik; Bienko, Magda; Crosetto, Nicola; Yan, Winston Xia; Scott, David Arthur; Li, Yinqing; Gao, Linyi; Federova, Yana; Zetsche, Bernd; Zhang, Feng
    Precisely measuring the location and frequency of DNA double-strand breaks (DSBs) along the genome is instrumental to understanding genomic fragility, but current methods are limited in versatility, sensitivity or practicality. Here we present Breaks Labeling In Situ and Sequencing (BLISS), featuring the following: (1) direct labelling of DSBs in fixed cells or tissue sections on a solid surface; (2) low-input requirement by linear amplification of tagged DSBs by in vitro transcription; (3) quantification of DSBs through unique molecular identifiers; and (4) easy scalability and multiplexing. We apply BLISS to profile endogenous and exogenous DSBs in low-input samples of cancer cells,...

  20. Thinking about seeing: Perceptual sources of knowledge are encoded in the theory of mind brain regions of sighted and blind adults

    Bedny, Marina; Koster-Hale, Jorie; Saxe, Rebecca R
    Blind people's inferences about how other people see provide a window into fundamental questions about the human capacity to think about one another's thoughts. By working with blind individuals, we can ask both what kinds of representations people form about others' minds, and how much these representations depend on the observer having had similar mental states themselves. Thinking about others' mental states depends on a specific group of brain regions, including the right temporo-parietal junction (RTPJ). We investigated the representations of others' mental states in these brain regions, using multivoxel pattern analyses (MVPA). We found that, first, in the RTPJ...

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