Now showing items 3837-3856 of 18256

    • Direct Imaging of Human SWI/SNF-Remodeled Mono- and Polynucleosomes by Atomic Force Microscopy Employing Carbon Nanotube Tips 

      Schnitzler, Gavin R.; Cheung, Chin Li; Hafner, Jason H.; Saurin, Andrew J.; Kingston, Robert E.; Lieber, Charles (American Society for Microbiology, 2001)
      Chromatin-remodeling complexes alter chromatin structure to facilitate, or in some cases repress, gene expression. Recent studies have suggested two potential pathways by which such regulation might occur. In the first, ...
    • Direct imaging of repulsive and attractive colloidal glasses 

      Kaufman, Laura J.; Weitz, David A. (AIP Publishing, 2006)
      Coherent anti-Stokes Raman scattering microscopy is performed on glassy systems of poly(methylmethacrylate) colloidal particles in density- and refractive-index-matched solvents. Samples are prepared with varying amounts ...
    • Direct Injection Tunnel Spectroscopy of a p-n Junction 

      Likovich, Edward Michael; Russell, Kasey Joe; Narayanamurti, Venkatesh; Lu, Hong; Gossard, Arthur C. (American Institute of Physics, 2009)
      We demonstrate spectroscopic measurements on an InGaAs p-n junction using direct tunnel injection of electrons. In contrast to the metal-base transistor design of conventional ballistic electron emission spectroscopy (BEES), ...
    • Direct Interaction of FliX and FlbD is Required for Their Regulatory Activity in Caulobacter crescentus 

      Xu, Zhaohui; Dutton, Rachel Janelle; Gober, James W (BioMed Central, 2011)
      Background: The temporal and spatial expression of late flagellar genes in Caulobacter crescentus is activated by the transcription factor FlbD and its partner trans-acting factor FliX. The physical interaction of these ...
    • Direct Interfacial Y731 Oxidation in α2 by a Photoβ2 Subunit of E. Coli Class Ia Ribonucleotide Reductase 

      Song, David Y.; Pizano, Arturo A.; Holder, Patrick G.; Stubbe, JoAnne; Nocera, Daniel (Royal Society of Chemistry (RSC), 2015)
      Proton-coupled electron transfer (PCET) is a fundamental mechanism important in a wide range of biological processes including the universal reaction catalysed by ribonucleotide reductases (RNRs) in making de novo, the ...
    • Direct Measurement of Cosmological Parameters from the Cosmic Deceleration of Extragalactic Objects 

      Loeb, Abraham (American Astronomical Society, 1998)
      The redshift of all cosmological sources drifts by a systematic velocity of order a few meters per second over a century as a result of the deceleration of the universe. The specific functional dependence of the predicted ...
    • Direct measurement of crystal surface stress 

      Martinez, Robert; Augustyniak, Walter; Golovchenko, Jene Andrew (American Physical Society (APS), 1990)
      We have measured surface stresses on clean Si(111) 7×7 by comparing this surface to a reference surface on which gallium atoms are adsorbed under UHV conditions. Stresses are determined by optically measuring the macroscopic ...
    • Direct measurement of local oxygen concentration in the bone marrow of live animals 

      Spencer, Joel A.; Ferraro, Francesca; Roussakis, Emmanuel; Klein, Alyssa; Wu, Juwell; Runnels, Judith M.; Zaher, Walid; Mortensen, Luke J.; Alt, Clemens; Turcotte, Raphaël; Yusuf, Rushdia; Côté, Daniel; Vinogradov, Sergei A.; Scadden, David T.; Lin, Charles P. (2014)
      Characterizing how the microenvironment, or niche, regulates stem cell activity is central to understanding stem cell biology and to developing strategies for therapeutic manipulation of stem cells1. Low oxygen tension ...
    • Direct measurement of the Zak phase in topological Bloch bands 

      Atala, Marcos; Aidelsburger, Monika; Barreiro, Julio T.; Abanin, Dmitry; Kitagawa, Takuya; Demler, Eugene A.; Bloch, Immanuel (Nature Publishing Group, 2013)
      Geometric phases that characterize the topological properties of Bloch bands play a fundamental role in the band theory of solids. Here we report on the measurement of the geometric phase acquired by cold atoms moving in ...
    • Direct Observation of a Long-Lived Single-Atom Catalyst Chiseling Atomic Structures in Graphene 

      Wang, Wei Li; Santos, Elton J. G.; Jiang, Bin; Cubuk, Ekin Dogus; Ophus, Colin; Centeno, Alba; Pesquera, Amaia; Zurutuza, Amaia; Ciston, Jim; Westervelt, Robert M.; Kaxiras, Efthimios (American Chemical Society (ACS), 2014)
      Fabricating stable functional devices at the atomic scale is an ultimate goal of nanotechnology. In biological processes, such high-precision operations are accomplished by enzymes. A counterpart molecular catalyst that ...
    • Direct Observation of a Sharp Transition to Coherence in Dense Cores 

      Pineda, Jaime Eduardo; Goodman, Alyssa; Arce, Hector G.; Caselli, Paola; Foster, Jonathan B.; Myers, Philip C.; Rosolowsky, Erik W. (American Astronomical Society, 2010)
      We present \(NH_3\) observations of the B5 region in Perseus obtained with the Green Bank Telescope. The map covers a region large enough \((\sim 11'×14')\) that it contains the entire dense core observed in previous dust ...
    • Direct Observation of Entropic Stabilization of bcc Crystals Near Melting 

      Sprakel, Joris; Zaccone, Alessio; Spaepen, Frans; Schall, Peter; Weitz, David A. (American Physical Society, 2017)
      Crystals with low latent heat are predicted to melt from an entropically stabilized body-centered cubic symmetry. At this weakly first-order transition, strongly correlated fluctuations are expected to emerge, which could ...
    • Direct observation of extension and retraction of type IV pili 

      Skerker, Jeffrey M.; Berg, Howard C. (National Academy of Sciences, 2001)
      Type IV pill are thin filaments that extend from the poles of a diverse group of bacteria, enabling them to move at speeds of a few tenths of a micrometer per second. They are required for twitching motility. e,g,, in ...
    • Direct parsing of ID/LP grammars 

      Shieber, Stuart (Springer, 1984)
      The Immediate Dominance/Linear Precedence (ID/LP) formalism is a recent extension of Generalized Phrase Structure Grammar (GPSG) designed to perform some of the tasks previously assigned to metarules--for example, modeling ...
    • Direct phase-sensitive identification of a d-form factor density wave in underdoped cuprates 

      Fujita, K.; Hamidian, M. H.; Edkins, S. D.; Kim, C. K.; Kohsaka, Y.; Azuma, M.; Takano, M.; Takagi, H.; Eisaki, H.; Uchida, S.-i.; Allais, Andrea; Lawler, M. J.; Kim, E.-A.; Sachdev, Subir; Davis, J. C. S. (Proceedings of the National Academy of Sciences, 2014)
      The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved. However, evidence has been accumulating that this state may be an unconventional density wave. Here we carry out site-specific ...
    • Direct Photon Production With Effective Field Theory 

      Becher, Thomas; Schwartz, Matthew D (Springer Verlag, 2010)
      The production of hard photons in hadronic collisions is studied using Soft-Collinear Effective Theory (SCET). This is the first application of SCET to a physical, observable cross section involving energetic partons in ...
    • Direct Realism and Perceptual Consciousness. 

      Siegel, Susanna (Wiley-Blackwell, 2006)
    • Direct Reciprocity on Graphs 

      Ohtsuki, Hisashi; Nowak, Martin A. (Elsevier, 2007)
      Direct reciprocity is a mechanism for the evolution of cooperation based on the idea of repeated encounters between the same two individuals. Here we examine direct reciprocity in structured populations, where individuals ...
    • Direct Reciprocity with Costly Punishment: Generous Tit-for-Tat Prevails 

      Rand, David Gertler; Ohtsuki, Hisashi; Nowak, Martin A. (Elsevier, 2009)
      The standard model for direct reciprocity is the repeated Prisoner's Dilemma, where in each round players choose between cooperation and defection. Here we extend the standard framework to include costly punishment. Now ...
    • Direct recognition of homology between double helices of DNA in Neurospora crassa 

      Gladyshev, Eugene; Kleckner, Nancy (2014)
      Chromosomal regions of identical or nearly identical DNA sequence can preferentially associate with one another in the apparent absence of DNA breakage. Molecular mechanism(s) underlying such homology-dependent pairing ...