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Caltech Authors (132.208 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 49.765

  1. Measurement of tt production with additional jet activity, including b quark jets, in the dilepton decay channel using pp collisions at √s = 8 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Pierini, M.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    Jet multiplicity distributions in top quark pair (tt) events are measured in pp collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC using a data set corresponding to an integrated luminosity of 19.7fb^(-1). The measurement is performed in the dilepton decay channels (e^+e^−, μ^+μ^−, and e^±μ^∓). The absolute and normalized differential cross sections for tt production are measured as a function of the jet multiplicity in the event for different jet transverse momentum thresholds and the kinematic properties of the leading additional jets. The differential ttb and ttbb cross sections are presented for the...

  2. Visual statistical learning produces implicit and explicit knowledge about temporal order information and scene chunks: Evidence from direct and indirect measures

    Otsuka, Sachio; Koch, Christof; Saiki, Jun
    We examined whether visual statistical learning (VSL) produced implicit and/or explicit knowledge about temporal order information and scene chunks, using a rapid serial visual presentation target detection task and a two-alternative forced-choice (2AFC) familiarity test as indirect and direct measures of VSL, respectively. In the familiarization phase, participants viewed a visual stream of natural scenes consisting of four triplets (i.e., three images that always appeared in the same order). In the subsequent target detection task, participants were required to detect target items embedded in a stream of 12 images or 12 words representing each natural scene. In the final 2AFC...

  3. Connecting Automatic Generation Control and Economic Dispatch From an Optimization View

    Li, Na; Zhao, Changhong; Chen, Lijun
    Automatic generation control (AGC) regulates mechanical power generation in response to load changes through local measurements. Its main objective is to maintain system frequency and keep energy balanced within each control area in order to maintain the scheduled net interchanges between control areas. The scheduled interchanges as well as some other factors of AGC are determined at a slower time scale by considering a centralized economic dispatch (ED) problem among different generators. However, how to make AGC more economically efficient is less studied. In this paper, we study the connections between AGC and ED by reverse engineering AGC from an...

  4. Measurement of inclusive jet production and nuclear modifications in pPb collisions at √sNN = 5.02 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.
    Inclusive jet production in pPb collisions at a nucleon–nucleon (NN) center-of-mass energy of √sNN = 5.02 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 30.1 nb^(−1) is analyzed. The jet transverse momentum spectra are studied in seven pseudorapidity intervals covering the range −2.0 < ηCM < 1.5 in the NN center-of-mass frame. The jet production yields at forward and backward pseudorapidity are compared and no significant asymmetry about η CM = 0 is observed in the measured kinematic range. The measurements in the pPb system are compared to reference...

  5. A model for regulation by SynGAP-α1 of binding of synaptic proteins to PDZ-domain 'Slots' in the postsynaptic density

    Walkup, Ward G., IV; Mastro, Tara L.; Schenker, Leslie T.; Vielmetter, Jost; Hu, Rebecca; Iancu, Ariella; Reghunathan, Meera; Bannon, B. Dylan; Kennedy, Mary B.
    SynGAP is a Ras/Rap GTPase-activating protein (GAP) that is a major constituent of postsynaptic densities (PSDs) from mammalian forebrain. Its α1 isoform binds to all three PDZ (PSD-95, Discs-large, ZO-1) domains of PSD-95, the principal PSD scaffold, and can occupy as many as 15% of these PDZ domains. We present evidence that synGAP-α1 regulates the composition of the PSD by restricting binding to the PDZ domains of PSD-95. We show that phosphorylation by Ca^(2+)/calmodulin-dependent protein kinase II (CaMKII) and Polo-like kinase-2 (PLK2) decreases its affinity for the PDZ domains by several fold, which would free PDZ domains for occupancy by...

  6. Distortion-Power Trade-Offs in Quasi-Stationary Source Transmission over Delay and Buffer Limited Block Fading Channels

    Joda, Roghayeh; Lahouti, Farshad; Erkip, Elza
    This paper investigates distortion-power tradeoffs in transmission of quasi-stationary sources over delay and buffer limited block fading channels by studying encoder and decoder buffering techniques to smooth out the source and channel variations. Four source and channel coding schemes that consider buffer and power constraints are presented to minimize the reconstructed source distortion. The first one is a high performance scheme, which benefits from optimized source and channel rate adaptation. In the second scheme, the channel coding rate is fixed and optimized along with transmission power with respect to channel and source variations; hence this scheme enjoys simplicity of implementation....

  7. Regional glutamine deficiency in tumours promotes dedifferentiation through inhibition of histone demethylation

    Pan, Min; Reid, Michael A.; Lowman, Xazmin H.; Kulkarni, Rajan P.; Tran, Thai Q.; Liu, Xiaojing; Yang, Ying; Hernandez-Davies, Jenny E.; Rosales, Kimberly K.; Li, Haiqing; Hugo, Willy; Song, Chunying; Xu, Xiangdong; Schones, Dustin E.; Ann, David K.; Gradinaru, Viviana; Lo, Roger S.; Locasale, Jason W.; Kong, Mei
    Poorly organized tumour vasculature often results in areas of limited nutrient supply and hypoxia. Despite our understanding of solid tumour responses to hypoxia, how nutrient deprivation regionally affects tumour growth and therapeutic response is poorly understood. Here, we show that the core region of solid tumours displayed glutamine deficiency compared with other amino acids. Low glutamine in tumour core regions led to dramatic histone hypermethylation due to decreased α-ketoglutarate levels, a key cofactor for the Jumonji-domain-containing histone demethylases. Using patient-derived ^(V600E)BRAF melanoma cells, we found that low-glutamine-induced histone hypermethylation resulted in cancer cell dedifferentiation and resistance to BRAF inhibitor treatment,...

  8. Characterization of Ti-Beta zeolites and their reactivity for the photocatalytic reduction of CO_2 with H_2O

    Ikeue, Keita; Yamashita, Hiromi; Takewaki, Takahiko; Davis, Mark E.; Anpo, Masakazu
    A characterization of Ti-Beta zeolites synthesized under various conditions as well as an investigation of their photocatalytic properties for the reduction of CO_2 with H_2O at 323 K to produce CH_4 and CH_3OH were carried out. In situ XAFS spectra measurements indicated that a highly dispersed tetrahedral titanium oxide species was present in the zeolite framework and an increase in the coordination number of the titanium oxide species by the addition of H_2O and CO_2 molecules could be detected. The Ti-Beta zeolite having a hydrophilic property (Ti-Beta(OH)) exhibited a more dramatic increase in the coordination number than the Ti-Beta(F) zeolite...

  9. Mo K- and L-edge X-ray absorption spectroscopic study of the ADP·AlF_4^−-stabilized nitrogenase complex: comparison with MoFe protein in solution and single crystal

    Corbett, Mary C.; Tezcan, F. Akif; Einsle, Oliver; Walton, Mika Y.; Rees, Douglas C.; Latimer, Matthew J.; Hedman, Britt; Hodgson, Keith O.
    The utility of using X-ray absorption spectroscopy (XAS) to study metalloproteins and, specifically, the enzyme complex nitrogenase, is highlighted by this study comparing both the structural and Mo-localized electronic features of the iron-molybdenum cofactor (FeMoco) in isolated MoFe protein and in the ADP·AlF_4^--stabilized complex of the MoFe protein with the Fe protein. No major differences are found at Mo between the two protein forms. The excellent quality of the data at both the Mo K and L edges will provide a baseline for analysis of other intermediates in the nitrogenase cycle. A new capability to delineate various contributions in the...

  10. UHF Deployable Helical Antennas for CubeSats

    Costantine, Joseph; Tawk, Youssef; Maqueda, Ignacio; Sakovsky, Maria; Olson, Gina; Pellegrino, Sergio; Christodoulou, Christos G.
    The design process and the deployment mechanism of a quadrifilar helix antenna (QHA) and a conical log spiral antenna (CLSA) are presented. The two antennas are proposed to operate in the UHF frequency band. They are composed of conductors that are embedded and supported by innovative structural techniques. This allows efficient folding, packaging, and deployment once in space. The conductors in the QHA are composed of beryllium copper and are supported by helical arms of S_2 glass fiber reinforced epoxy. The CLSA, on the other hand, has conductors that are made out of a mesh of phosphor bronze and incorporated...

  11. Density Functional Theory Study of the Geometry, Energetics, and Reconstruction Process of Si(111) Surfaces

    Solares, Santiago D.; Dasgupta, Siddharth; Schultz, Peter A.; Kim, Yong-Hoon; Musgrave, Charles B.; Goddard, William A.
    We report the structures and energies from first principles density functional calculations of 12 different reconstructed (111) surfaces of silicon, including the 3 × 3 to 9 × 9 dimer−adatom−stacking fault (DAS) structures. These calculations used the Perdew−Burke−Ernzerhof generalized gradient approximation of density functional theory and Gaussian basis functions. We considered fully periodic slabs of various thicknesses. We find that the most stable surface is the DAS 7 × 7 structure, with a surface energy of 1.044 eV/1 × 1 cell (1310 dyn/cm). To analyze the origins of the stability of these systems and to predict energetics for more complex,...

  12. μ-p scattering and the glue fraction of the proton

    Politzer, H. David
    The QCD version of the energy-momentum sum rule is tested against SLAC electroproduction and FNAL muon-proton scattering data. While providing only a single number for each Q2, the energy momentum sum rule is significant because the scaling violations due to gluons can be well determined. In particular, gluons carry 30±8% of the proton's energy-momentum at Q2=3.5 GeV2 (which means 22% at 1 GeV2). The largest single corrections of previous estimates of the glue fraction is the inclusion of gluon bremsstrahlung effects. Agreement with experiment is within the uncertainties in the μ-p data. However, the sum rule does not give a...

  13. Gluon corrections to Drell-Yan processes

    Politzer, H. David
    Assuming that the Drell-Yan picture is approximately valid, I compute the O(g^2) gluon radiative corrections in QCD. The corrections are self-consistent, i.e. they satisfy several non-trivial constraints necessary for the validity of the whole picture. There are logarithmic scaling violations in the quark distribution functions, precisely equal to those found in electroproduction. Large transverse momenta (of order of the c.m. energy) are produced, balanced by radiation in the opposite direction. I compute the transverse momentum differential cross section for μ pairs as an example

  14. Measurement of the differential cross sections for top quark pair production as a function of kinematic event variables in pp collisions at √s = 7 and 8 TeV

    Khachatryan, V.; Anderson, D.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Pierini, M.; Spiropulu, M.; Vlimant, J. R.; Xie, S.; Zhu, R. Y.; Dubinin, M.
    Measurements are reported of the normalized differential cross sections for top quark pair production with respect to four kinematic event variables: the missing transverse energy; the scalar sum of the jet transverse momentum (p_T); the scalar sum of the p_T of all objects in the event; and the p T of leptonically decaying W bosons from top quark decays. The data sample, collected using the CMS detector at the LHC, consists of 5.0  fb^(−1) of proton-proton collisions at √s=7  TeV and 19.7  fb^(−1) at √s=8  TeV. Top quark pair events containing one electron or muon are selected. The results are presented after correcting for...

  15. The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star-forming Galaxies from z ~ 1 to z ~ 3

    Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia
    Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in damped Lyα systems (DLAs) at z ~ 3 is more than 10 times lower than predicted by the Kennicutt–Schmidt (KS) relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z ~ 1, z ~ 2, and z ~ 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and...

  16. Neural mechanisms and personality correlates of the sunk cost effect

    Fujino, Junya; Fujimoto, Shinsuke; Kodaka, Fumitoshi; Camerer, Colin F.; Kawada, Ryosaku; Tsurumi, Kosuke; Tei, Shisei; Isobe, Masanori; Miyata, Jun; Sugihara, Genichi; Yamada, Makiko; Fukuyama, Hidenao; Murai, Toshiya; Takahashi, Hidehiko
    The sunk cost effect, an interesting and well-known maladaptive behavior, is pervasive in real life, and thus has been studied in various disciplines, including economics, psychology, organizational behavior, politics, and biology. However, the neural mechanisms underlying the sunk cost effect have not been clearly established, nor have their association with differences in individual susceptibility to the effect. Using functional magnetic resonance imaging, we investigated neural responses induced by sunk costs along with measures of core human personality. We found that individuals who tend to adhere to social rules and regulations (who are high in measured agreeableness and conscientiousness) are more...

  17. CLASH-VLT: Dissecting the Frontier Fields Galaxy Cluster MACS J0416.1-2403 with ∼800 Spectra of Member Galaxies

    Balestra, I.; Medezinski, E.; Zitrin, A.
    We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields cluster MACS J0416.1-2403 (z = 0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ~600 arcmin^2, including ~800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ~2.2 r _(200) (~4 Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster (M _(200) ~ 0.9 × 10^(15) M_⊙ and σ_(V,r200) ~ 1000 km s^(−1)) presenting...

  18. The COSMOS2015 Catalog: Exploring the 1 < z < 6 Universe with Half a Million Galaxies

    Laigle, C.; Capak, P.; Scoville, N.
    We present the COSMOS2015 catalog, which contains precise photometric redshifts and stellar masses for more than half a million objects over the 2deg^2 COSMOS field. Including new YJHK_s images from the UltraVISTA-DR2 survey, Y-band images from Subaru/Hyper-Suprime-Cam, and infrared data from the Spitzer Large Area Survey with the Hyper-Suprime-Cam Spitzer legacy program, this near-infrared-selected catalog is highly optimized for the study of galaxy evolution and environments in the early universe. To maximize catalog completeness for bluer objects and at higher redshifts, objects have been detected on a χ^2 sum of the YJHK_s and z^(++) images. The catalog contains ~6 x...

  19. The AllWISE Motion Survey, Part 2

    Kirkpatrick, J. Davy; Kellogg, Kendra; Schneider, Adam C.; Fajardo-Acosta, Sergio; Cushing, Michael C.; Greco, Jennifer; Mace, Gregory N.; Gelino, Christopher R.; Wright, Edward L.; Eisenhardt, Peter R. M.; Stern, Daniel; Faherty, Jacqueline K.; Sheppard, Scott S.; Lansbury, George B.; Logsdon, Sarah E.; Martin, Emily C.; McLean, Ian S.; Schurr, Steven D.; Cutri, Roc M.; Conrow, Tim
    We use the AllWISE Data Release to continue our search for Wide-field Infrared Survey Explorer (WISE)-detected motions. In this paper, we publish another 27,846 motion objects, bringing the total number to 48,000 when objects found during our original AllWISE motion survey are included. We use this list, along with the lists of confirmed WISE-based motion objects from the recent papers by Luhman and by Schneider et al., and candidate motion objects from the recent paper by Gagné et al., to search for widely separated, common-proper-motion systems. We identify 1039 such candidate systems. All 48,000 objects are further analyzed using color–color...

  20. Morphology and Molecular Gas Fractions of Local Luminous Infrared Galaxies as a Function of Infrared Luminosity and Merger Stage

    Larson, K. L.; Sanders, D. B.; Barnes, J. E.; Ishida, C. M.; Evans, A. S.; U, V.; Mazzarella, J. M.; Kim, D.-C.; Privon, G. C.; Mirabel, I. F.; Flewelling, H. A.
    We present a new, detailed analysis of the morphologies and molecular gas fractions (MGFs) for a complete sample of 65 local luminous infrared galaxies from Great Observatories All-Sky Luminous Infrared Galaxies (LIRG) Survey using high resolution I-band images from The Hubble Space Telescope, the University of Hawaii 2.2 m Telescope and the Pan-STARRS1 Survey. Our classification scheme includes single undisturbed galaxies, minor mergers, and major mergers, with the latter divided into five distinct stages from pre-first pericenter passage to final nuclear coalescence. We find that major mergers of molecular gas-rich spirals clearly play a major role for all sources with...

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