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Caltech Authors (92,886 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 36,158

1. The role played by fast electrons in heavy-ion-induced desorption and track formation - Tombrello, T. A.
We have substantial evidence that ion damage tracks and ion-induced desorption are consequences of the electronic excitation that is caused by the incident ion's impact on the target. This is shown by the correlation of the desorption yield/track damage with the energy loss of the ion to electrons during its slowing down process; the extended size of the desorbed molecules and the diameter of the tracks show that the transport of energy away from the ion's path is mediated by these secondary electrons. Experimental studies show that the distribution of damage along an ion track is not uniform, which suggests...

2. The rotation group in plate tectonics and the representation of uncertainties of plate reconstructions - Chang, T.; Stock, J.; Molnar, P.
The calculation of the uncertainty in an estimated rotation requires a parametrization of the rotation group; that is, a unique mapping of the rotation group to a point in 3-D Euclidean space, R^3. Numerous parametrizations of a rotation exist, including: (1) the latitude and longitude of the axis of rotation and the angle of rotation; (2) a representation as a Cartesian vector with length equal to the rotation angle and direction parallel to the rotation axis; (3) Euler angles; or (4) unit length quaternions (or, equivalently, Cayley-Klein parameters). The uncertainty in a rotation is determined by the effect of nearby...

3. Geomorphic evolution of a storm-dominated carbonate ramp (c. 549 Ma), Nama Group, Namibia - Dibenedetto, S.; Grotzinger, J.
The well-exposed Hoogland Member (c. 549 Ma) of the northern Nama Group (Kuibis Subgroup), Namibia, represents a storm-dominated carbonate ramp developed in a foreland basin of terminal Proterozoic age. The ramp displays facies gradients involving updip grainstones which pass downdip into broad, spatially extensive tracts of microbial laminites and finely laminated mudstones deposited above and below storm wave base. Trough cross-bedded, coarse grainstones are shown to transit downdip into finer-grained calcarenites, irregular microbial laminites and mottled laminites. Siliciclastic siltstones and shales were deposited further downdip. Platform growth was terminated through smothering by orogen-derived siliciclastic deposits. Ramp morphology was controlled by...

4. Design and characterization of structured protein linkers with differing flexibilities - Klein, Joshua S.; Jiang, Siduo; Galimidi, Rachel P.; Keeffe, Jennifer R.; Bjorkman, Pamela J.
Engineered fusion proteins containing two or more functional polypeptides joined by a peptide or protein linker are important for many fields of biological research. The separation distance between functional units can impact epitope access and the ability to bind with avidity; thus the availability of a variety of linkers with different lengths and degrees of rigidity would be valuable for protein design efforts. Here, we report a series of designed structured protein linkers incorporating naturally occurring protein domains and compare their properties to commonly used Gly_4Ser repeat linkers. When incorporated into the hinge region of an immunoglobulin G (IgG) molecule,...

5. Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing site to Backstay Rock in the Columbia Hills - Arvidson, R. E.; Grotzinger, J.
Spirit landed on the floor of Gusev Crater and conducted initial operations on soil-covered, rock-strewn cratered plains underlain by olivine-bearing basalts. Plains surface rocks are covered by wind-blown dust and show evidence for surface enrichment of soluble species as vein and void-filling materials and coatings. The surface enrichment is the result of a minor amount of transport and deposition by aqueous processes. Layered granular deposits were discovered in the Columbia Hills, with outcrops that tend to dip conformably with the topography. The granular rocks are interpreted to be volcanic ash and/or impact ejecta deposits that have been modified by aqueous...

6. Physical conditions of molecular gas in the Circinus galaxy Multi-J CO and Ci ^3P_1 →^3P_0 observations - Zhang, Zhi-Yu; Henkel, Christian; Gao, Yu; Güsten, Rolf; Menten, Karl M.; Papadopoulos, Padelis P.; Zhao, Yinghe; Ao, Yipin; Kaminski, Tomasz
We report mapping observations of the ^(12)CO J = 3 → 2, 4 → 3, 6 → 5, and 7 → 6 transitions and the Ci ^3P→^3P_0 (Ci) 492GHz transition toward the central 40" × 40" region of the Circinus galaxy, using the Atacama Pathfinder EXperiment (APEX) telescope. We also detected ^(13)COJ = 3 → 2 at the central position of Circinus. These observations are to date the highest CO transitions reported in Circinus. With large velocity gradient (LVG) modeling and likelihood analysis we try to obtain density, temperature, and column density of the molecular gas in three regions: the...

7. Modeling regional aerosol and aerosol precursor variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns - Fast, J. D.; Craven, J.; Metcalf, A.; Seinfeld, J.
The performance of the Weather Research and Forecasting regional model with chemistry (WRF-Chem) in simulating the spatial and temporal variations in aerosol mass, composition, and size over California is quantified using the extensive meteorological, trace gas, and aerosol measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010. The overall objective of the field campaigns was to obtain data needed to better understand processes that affect both climate and air quality, including emission assessments, transport and chemical aging of aerosols, aerosol...

8. Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanet - Fraine, Jonathan; Deming, Drake; Benneke, Björn; Knutson, Heather; Jordán, Andrés; Espinoza, Néstor; Madhusudhan, Nikku; Wilkins, Ashlee; Todorov, Kamen
Transmission spectroscopy has so far detected atomic and molecular absorption in Jupiter-sized exoplanets, but intense efforts to measure molecular absorption in the atmospheres of smaller (Neptune-sized) planets during transits have revealed only featureless spectra. From this it was concluded that the majority of small, warm planets evolve to sustain atmospheres with high mean molecular weights (little hydrogen), opaque clouds or scattering hazes, reducing our ability to observe the composition of these atmospheres. Here we report observations of the transmission spectrum of the exoplanet HAT-P-11b (which has a radius about four times that of Earth) from the optical wavelength range to...

9. The applicability of far-infrared fine-structure lines as star formation rate tracers over wide ranges of metallicities and galaxy types - De Looze, Ilse; Cornier, Diane; Lebouteiller, Vianney; Madden, Suzanne; Baes, Marten; Bendo, George J.; Boquien, Médéric; Boselli, Alessandro; Clements, David L.; Cortese, Luca; Cooray, Asantha; Galametz, Maud; Galliano, Frédéric; Graciá-Carpio, Javier; Isaak, Kate; Karczewski, Oskar Ł.; Parkin, Tara J.; Pellegrini, Eric W.; Rémy-Ruyer, Aurélie; Spinoglio, Luigi; Smith, Matthew W. L.; Sturm, Eckhard
Aims. We analyze the applicability of far-infrared fine-structure lines [Cii] 158 μm, [Oi] 63 μm, and [Oiii] 88 μm to reliably trace the star formation rate (SFR) in a sample of low-metallicity dwarf galaxies from the Herschel Dwarf Galaxy Survey and, furthermore, extend the analysis to a broad sample of galaxies of various types and metallicities in the literature. Methods. We study the trends and scatter in the relation between the SFR (as traced by GALEX FUV and MIPS 24 μm) and far-infrared line emission, on spatially resolved and global galaxy scales, in dwarf galaxies. We assemble far-infrared line measurements from the literature and infer whether...

10. A time to find solutions - Bacher, Robert F.
Carroll Wilson's article, Nuclear Energy: What Went Wrong (Bulletin. June 1979), is both interesting and perceptive. He points out quite correctly that at least two of the most criticized areas at the back end of the fuel cycle--reprocessing and nuclear wastes--required much more attention than was given. Also he Points out that for nuclear power the whole cycle must work. His comments on control rooms are well taken in addition to his comparison to the vastly more complicated Boeing 747. The quality and training of operators have now been singled out for special criticism in the recent Kemeny Report on the Three Mile Island accident.

11. On the reduction of nuclear weapons - Bacher, Robert F.
The United States, in 1946, proposed that an international authority be formed to control the dangerous parts of atomic energy. The proposal met with very little success, except to lead to the conclusion that there was no apparent reason why it was not technically feasible. Discussions on nuclear weapons testing, initiated in 1958, reached some agreement on test restrictions in Subsequent years.

12. Seawater desalination plant for Southern California - Hammond, R. Philip; Eissenberg, David M.; Emmermann, Dieter K.; Jones, John E., Jr.; Sephton, Hugo H.; Standiford, Ferric C.; Scott, Ronald F.; Rider, William J.; Dean, David W.
The paper describes Metropolitan's $30 million demonstration program to develop a 75 million-gallon-per-day (mgd) seawater desalination plant coupled to a combined cycle steam turbine coastal power generating plant that produces water at $600 per acre foot. The plant is a multi-effect distillation process incorporating a thirty-effect, vertically stacked evaporator in a concrete pressure vessel using vertical aluminum double-fluted bundles.

13. President's Science Advisory Committee Revisited - Golden, William T.; Bacher, Robert F.; Bethe, Hans A.; Goodpaster, Andrew J.; Killian, James R., Jr.; Piore, Emanuel R.; Rabi, Isidore I.
On 30 March 1984, Hofstra University sponsored a panel discussion on the "President's Science Advisory Committee Revisited," during a university conference on the Eisenhower Presidency. Participants in the panel discussion were: Robert F. Bacher, Andrew J. Goodpaster, Emanuel R. Piore, Isidor I. Rabi, and William T. Golden, chairman. James R. Killian, Jr., and Hans A. Bethe were to have participated but were unable to do so at the last minute; both men have graciously written new commentaries especially for this issue. The messages contained in the following edited transcript are clear and timely. First, President Eisenhower recognized that he benefited...

14. Rapid expansion of a cylindrical cavity in a rate-type soil - Davis, R. O.; Scott, R. F.; Mullenger, G.
An analytical solution for rapid (undrained) expansion of a long cylindrical cavity from initially zero radius is presented. A simple rate-type soil model possessing the salient features of the modified Cambridge critical state model is used. Application of the solution to determination of the stress field surrounding a pile immediately after driving is discussed.

15. Rapid Shearing in a Rate-Type Soil Surrounding a Cylindrical Cavity - Mullenger, G.; Scott, R. F.; Davis, R. O.
The stress and deformation resulting from rapidly applied axial traction on the face of a cylindrical cavity in a saturated soil are analysed. A simple rate-type constitutive model is used for the effective stress response.

16. Finite element simulation of Wilmington oil field subsidence: I. Linear modelling - Kosloff, Dan; Scott, R. F.; Scranton, J.
The Wilmington oil field in Long Beach California has been a site of large ground subsidence since the onset of production. The cause of the subsidence has been attributed to the lowering of pore fluid pressures in the formations of the field. In this study the subsidence in the Wilmington field is simulated numerically by solving the equilibrium equations for a region of the earth's crust containing the oil field. The input parameters for the calculation include a linearly elastic rheological mode for the formations of the field and pore pressure values at the producing zones at specified times. It...

17. Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at √s=8TeV - Chatrchyan, S.; Apresyan, A.; Bornheim, A.; Bunn, J.; Chen, Y.; Di Marco, E.; Duarte, J.; Mott, A.; Newman, H. B.; Pena, C.; Rogan, C.; Spiropulu, M.; Timciuc, V.; Wilkinson, R.; Xie, S.; Zhu, R. Y.; Dias, F. A.; Dubinin, M.
A search for supersymmetry through the direct pair production of top squarks, with Higgs (H) or Z bosons in the decay chain, is performed using a data sample of proton–proton collisions at √s=8TeV collected in 2012 with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 19.5fb^(−1). The search is performed using a selection of events containing leptons and bottom-quark jets. No evidence for a significant excess of events over the standard model background prediction is observed. The results are interpreted in the context of simplified supersymmetric models with pair production of a heavier top-squark...

18. Finite element simulation of Wilmington oil field subsidence: II. Nonlinear modelling - Kosloff, D.; Scott, R. F.; Scranton, J.
The numerical modelling of the first part of this work is extended to include a nonlinear elastic—plastic material response. The parameters for the rheological model are deduced from published soil tests and from the behavior of the field during the rebound phase which is assumed to be purely elastic. Unlike the linear case, the response of the plastic model is highly dependent on the stresses in the field prior to production. When these stresses are purely lithostatic and horizontally uniform the fit to observations is not significantly improved over the linear models. When a flexural prestress which accounts for the...

19. The Baldwin Hills reservoir failure - Hoye, Walter; Leps, T. M.; Willis, Homer; Scott, R. F.; Leonards, G. A.; Muria, Juan
Walter Hoye, Los Angeles DWP: Let me tell you about my involvement at the time of the Baldwin Hills Reservoir failure. I was studying for my first promotional exam at the University of Southern California library. I was an entry level engineer at the Department of Water and Power. Well, here I am 22 years later, I am the Engineer of Design in charge of dam safety. I was concerned then and I am really concerned now. I am responsible for all of our dams in the city and all of the dams we have along the 300 miles of aqueduct that bring water from the Sierras to...

20. The Baldwin Hills reservoir failure - Scott, R. F.
I think it would be a good idea if I start by describing what my affiliation with Baldwin Hills was. The failure happened, as we know, in December 1963. Within a day or so after the failure the mayor of Los Angeles under (as you might understand) certain pressures formed what was called locally, "a blue-ribbon committee". It consisted of several professors from different universities around the Los Angeles area and was chaired by a retired judge. It had a lawyer in the group, and representatives of different areas among the professors: the seismic, soil mechanics (me), and geology areas, and a professor who was in the petroleum...

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