Recursos de colección

Books by Caltech Authors (234 recursos)

This site is an institutional repository providing access to the book (monograph) publication output of Caltech. As is the nature of the institute whiles these books cover many different subjects, the majority are concerned with issues of the applied scientific disciplines. Part of the Caltech Online Digital Archives (CODA) project.

Type = Article

Mostrando recursos 1 - 14 de 14

  1. Homeostatic cytokines orchestrate the segregation of CD4 and CD8 memory T-cell reservoirs in mice

    Yang, Lili; Yu, Yang; Kalwani, Manorama; Tseng, Tai-Wei Joy; Baltimore, David
    Memory T cells (T_Ms) have been detected in many tissues but their quantitative distribution remains largely undefined. We show that in mice there is a remarkably biased accumulation of long-term CD4 T_Ms into mucosal sites (mainly gut, especially Peyer patches), and CD8 T_Ms into lymph nodes and spleen (in particular, peripheral lymph nodes [PLNs]). This distinction correlates with their differentiated expression of PLN- and gut-homing markers. CD8 and CD4 T_Ms selectively require the expression of PLN-homing marker CCR7 or gut-homing marker α4β7 for maintenance. PLNs and gut supply CD8 and CD4 T_Ms with their individually favored homeostatic cytokine, IL-15, or...

  2. MicroRNA function in myeloid biology

    O'Connell, Ryan M.; Zhao, Jimmy L.; Rao, Dinesh S.
    The past 5 years have seen an explosion of knowledge about miRNAs and their roles in hematopoiesis, cancer, and other diseases. In myeloid development, there is a growing appreciation for both the importance of particular miRNAs and the unique features of myelopoiesis that are being uncovered by experimental manipulation of miRNAs. Here, we review in detail the roles played by 4 miRNAs, miR-125, miR-146, miR-155, and miR-223 in myeloid development and activation, and correlate these roles with their dysregulation in disease. All 4 miRNAs demonstrate effects on myelopoiesis, and their loss of function or overexpression leads to pathologic phenotypes in the myeloid...

  3. Steady-state invariant genetics: probing the role of morphogen gradient dynamics in developmental patterning

    Nahmad, Marcos
    Morphogen-mediated patterning is the predominant mechanism by which positional information is established during animal development. In the classical view, the interpretation of positional signals depends on the equilibrium distribution of a morphogen, regardless of the dynamics of gradient formation. The problem of whether or not morphogen dynamics contribute to developmental patterning has not been explored in detail, partly because genetic experiments, which selectively affect signalling dynamics while maintaining unchanged the steady-state morphogen profile, are difficult to design and interpret. Here, I present a modelling-based approach to identify genetic mutations in developmental patterning that may affect the transient, but leave invariant the steady-state...

  4. Average crack-front velocity during subcritical fracture propagation in a heterogeneous medium

    Lengliné, Olivier; Toussaint, Renaud; Schmittbuhl, Jean; Elkhoury, Jean E.; Ampuero, J. P.; Tallakstad, Ken Tore; Santucci, Stéphane; Måløy, Knut Jørgen
    We study the average velocity of crack fronts during stable interfacial fracture experiments in a heterogeneous quasibrittle material under constant loading rates and during long relaxation tests. The transparency of the material (polymethylmethacrylate) allows continuous tracking of the front position and relation of its evolution to the energy release rate. Despite significant velocity fluctuations at local scales, we show that a model of independent thermally activated sites successfully reproduces the large-scale behavior of the crack front for several loading conditions.

  5. Exploring the Galaxy Mass-Metallicity Relations at z ~ 3-5

    Laskar, Tanmoy; Berger, Edo; Chary, Ranga-Ram
    Long-duration gamma-ray bursts (GRBs) provide a premier tool for studying high-redshift star-forming galaxies thanks to their extreme brightness and association with massive stars. Here we use GRBs to study the galaxy stellar mass-metallicity (M_*-Z) relation at z ~ 3-5, where conventional direct metallicity measurements are extremely challenging. We use the interstellar medium metallicities of long GRB hosts derived from afterglow absorption spectroscopy, in conjunction with host galaxy stellar masses determined from deep Spitzer 3.6 μm observations of 20 GRB hosts. We detect about 1/4 of the hosts with M_(AB)(I) ≈ –21.5 to –22.5 mag and place a limit of M_(AB)(I)...

  6. The Origin of [O II] Emission in Recently Quenched Active Galaxy Nucleus Hosts

    Kocevski, Dale D.; Lemaux, Brian C.; Lubin, Lori M.; Shapley, Alice E.; Gal, Roy R.; Squires, Gordon K.
    We have employed emission-line diagnostics derived from DEIMOS and NIRSPEC spectroscopy to determine the origin of the [O II] emission line observed in six active galactic nucleus (AGN) hosts at z ~ 0.9. These galaxies are a subsample of AGN hosts detected in the Cl1604 supercluster that exhibit strong Balmer absorption lines in their spectra and appear to be in a post-starburst or post-quenched phase, if not for their [O II] emission. Examining the flux ratio of the [N II] to Hα lines, we find that in five of the six hosts the dominant source of ionizing flux is AGN...

  7. A Sunyaev-Zel'Dovich-Selected Sample of the Most Massive Galaxy Clusters in the 2500 deg^2 South Pole Telescope Survey

    Williamson, R.; Padin, S.; Vieira, J. D.
    The South Pole Telescope (SPT) is currently surveying 2500 deg^2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg^2 at the final SPT survey depth of 18 μK arcmin at 150 GHz and 1000 deg^2 at a depth of 54...

  8. Constraint on the Assembly and Dynamics of Galaxies. II. Properties of Kiloparsec-Scale Clumps in Rest-Frame Optical Emission of z ~ 2 Star-Forming Galaxies

    Förster Schreiber, N. M.; Shapley, A. E.; Genzel, R.; Bouché, N.; Cresci, G.; Davies, R.; Erb, D. K.; Genel, S.; Lutz, D.; Newman, S.; Shapiro, K. L.; Steidel, C. C.; Sternberg, A.; Tacconi, L. J.
    We study the properties of luminous stellar "clumps" identified in deep, high-resolution Hubble Space Telescope NIC2/F160W imaging at 1.6 μm of six z ~ 2 star-forming galaxies with existing near-infrared integral field spectroscopy from SINFONI at the Very Large Telescope. Individual clumps contribute ~0.5%-15% of the galaxy-integrated rest-frame ≈5000 Å emission, with median of ≈2%; the total contribution of clump light ranges from 10% to 25%. The median intrinsic clump size and stellar mass are ~1 kpc and ~10^9 M_☉, in the ranges for clumps identified in rest-UV or line emission in other studies. The clump sizes and masses in...

  9. Graphene Plasmonics: A Platform for Strong Light-Matter Interactions

    Koppens, Frank H. L.; Chang, Darrick E.; García de Abajo, F. Javier
    Graphene plasmons provide a suitable alternative to noble-metal plasmons because they exhibit much tighter confinement and relatively long propagation distances, with the advantage of being highly tunable via electrostatic gating. Here, we propose to use graphene plasmons as a platform for strongly enhanced light–matter interactions. Specifically, we predict unprecedented high decay rates of quantum emitters in the proximity of a carbon sheet, observable vacuum Rabi splittings, and extinction cross sections exceeding the geometrical area in graphene nanoribbons and nanodisks. Our theoretical results provide the basis for the emerging and potentially far-reaching field of graphene plasmonics, offering an ideal platform for...

  10. Synthesis and Characterization of Three-Coordinate Ni(III)-Imide Complexes

    Iluc, Vlad M.; Miller, Alexander J. M.; Anderson, John S.; Monreal, Marisa J.; Mehn, Mark P.; Hillhouse, Gregory L.
    A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the...

  11. Coupling backbone flexibility and amino acid sequence selection in protein design

    Su, Alyce; Mayo, Stephen L.
    Using a protein design algorithm that considers side-chain packing quantitatively, the effect of explicit backbone motion on the selection of amino acids in protein design was assessed in the core of the streptococcal protein G β1 domain (Gβ1). Concerted backbone motion was introduced by varying Gβ1's supersecondary structure parameter values. The stability and structural flexibility of seven of the redesigned proteins were determined experimentally and showed that core variants containing as many as 6 of 10 possible mutations retain native-like properties. This result demonstrates that backbone flexibility can be combined explicitly with amino acid side-chain selection and that the selection...

  12. Pairwise calculation of protein solvent-accessible surface areas

    Street, Arthur G.; Mayo, Stephen L.
    Background: The tractability of many algorithms for determining the energy state of a system depends on the pairwise nature of an energy expression. Some energy terms, such as the standard implementation of the van der Waals potential, satisfy this criterion whereas others do not. One class of important potentials that are not pairwise involves benefits and penalties for burying hydrophobic and/or polar surface areas. It has been found previously that, in some cases, a pairwise approximation to these surface areas correlates with the true surface areas. We set out to generalize the applicability of this approximation. Results: We develop a pairwise...

  13. De novo protein design: towards fully automated sequence selection

    Dahiyat, Bassil I.; Sarisky, Catherine A.; Mayo, Stephen L.
    Several groups have applied and experimentally tested systematic, quantitative methods to protein design with the goal of developing general design algorithms. We have sought to expand the range of computational protein design by developing quantitative design methods for residues of all parts of a protein: the buried core, the solvent exposed surface, and the boundary between core and surface. Our goal is an objective, quantitative design algorithm that is based on the physical properties that determine protein structure and stability and which is not limited to specific folds or motifs. We chose the ββα motif typified by the zinc finger...

  14. A designed apoplastocyanin variant that shows reversible folding

    Datta, Deepshikha; Mayo, Stephen L.
    Plastocyanin, like many other metalloproteins, does not undergo reversible folding, which is thought to be due to an irreversible conformational change in the copper-binding site. Moreover, apoplastocyanin's ability to adopt a native tertiary structure is highly salt-dependent, and even in high salt, it has an irreversible thermal denaturation. Here, we report a designed apoplastocyanin variant, PCV, that is well folded and has reversible folding in both high and low salt conditions. This variant provides a tractable model for understanding and designing protein β-sheets.

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