Recursos de colección

Caltech Authors (132,782 recursos)

Repository of works by Caltech published authors.

Type = Article

Mostrando recursos 481 - 500 de 506

  1. Planktonic and sediment-associated aerobic methanotrophs in two seep systems along the North American margin

    Tavormina, Patricia L.; Ussler, William, III; Orphan, Victoria J.
    Methane vents are of significant geochemical and ecological importance. Notable progress has been made towards understanding anaerobic methane oxidation in marine sediments, however, the diversity and distribution of aerobic methanotrophs in the water column are poorly characterized. Both environments play an essential role in regulating methane release from the oceans to the atmosphere. In this study, the diversity of particulate methane monooxygenase (pmoA) and 16S rRNA genes from two methane vent environments along the California continental margin was characterized. The pmoA phylotypes recovered from methane-rich sediments and the overlying water column differed. Sediments harbored the greatest number of unique pmoA...

  2. DNA sequence of the mouse H-2Dd transplantation antigen gene

    Sher, Beverly Taylor; Nairn, Roderick; Coligan, John E.; Hood, Leroy E.
    The inbred BALB/c mouse has three transplantation antigens, H2-Kd, H2-Ld, and H2-Dd. We present the complete nucleotide sequence of the H2-Dd gene as well as 777 residues of previously unpublished H-2Dd protein sequence. These data complete the sequences of all the BALB/c transplantation antigen genes and permit detailed comparison with each other and with their counterparts from the inbred C57BL/10 mouse. Transplantation antigens may differ from one another by as much as 5%-15% of their amino acid sequence for the external domains. These extensive differences may arise by gene conversion. The H-2D region of the BALB/c mouse encodes the H2-Dd...

  3. Electron emission into dielectric liquids

    LePage, Wilbur R.; DuBridge, L. A.
    The current between polished nickel electrodes immersed in pure toluene has been measured as a function of electric field (over the range 0 to 250,000 volts/cm) and of temperature (from - 15 to 70°C). The Richardson lines are straight but show a very small slope (0.05 to 0.4 ev) and a small value of the constant A (10^-9 to 10^-11 amp./cm^2 deg.^2). The logi vs. E1 / 2 curves show a slope about twice the value e3 / 2 / D1 / 2kT predicted by the simple Schottky theory, but in agreement with the theory of Baker and Boltz. It...

  4. Evidence for multiple structural genes for the γ chain of human fetal hemoglobin

    Schroeder, W. A.; Huisman, T. H. J.; Shelton, J. Roger; Shelton, Joan Balog; Kleihauer, Enno F.; Dozy, Andrée M.; Robberson, Barbara
    A sequence with a specific residue at each position was proposed for the γ chain of human fetal hemoglobin by Schroeder et al. (1) after a study in which hemoglobin from a number of individual infants was used. We have now examined in part the fetal hemoglobin components of 17 additional infants and have observed that position 136 of the γ chain may be occupied not only by a glycyl residue, as previously reported, but also by an alanyl residue.

  5. dc readout experiment at the Caltech 40m prototype interferometer

    Ward, R. L.; Adhikari, Rana X.; Abbott, B.; Abbott, R.; Barron, D.; Bork, R.; Fricke, T.; Frolov, V.; Heefner, J.; Ivanov, A.; Miyakawa, O.; McKenzie, K.; Slagmolen, B.; Smith, M.; Taylor, R.; Vass, S.; Waldman, S.; Weinstein, Alan J.
    The Laser Interferometer Gravitational Wave Observatory (LIGO) operates a 40m prototype interferometer on the Caltech campus. The primary mission of the prototype is to serve as an experimental testbed for upgrades to the LIGO interferometers and for gaining experience with advanced interferometric techniques, including detuned resonant sideband extraction (i.e. signal recycling) and dc readout (optical homodyne detection). The former technique will be employed in Advanced LIGO, and the latter in both Enhanced and Advanced LIGO. Using dc readout for gravitational wave signal extraction has several technical advantages, including reduced laser and oscillator noise couplings as well as reduced shot noise,...

  6. Operational status of TAMA300 with the seismic attenuation system (SAS)

    Takahashi, R.; Arai, K.; Tatsumi, D.; Fukushima, M.; Yamazaki, T.; Fujimoto, M.-K.; Agatsuma, K.; Arase, Y.; Nakagawa, N.; Takamori, A.; Tsubono, K.; DeSalvo, R.; Bertolini, A.; Márka, S.; Saninbale, V.
    TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by seismic activities, we installed a new seismic isolation system —- the TAMA seismic attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled Fabry–Perot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS.

  7. Stabilized lasers for advanced gravitational wave detectors

    Willke, B.; Danzmann, K.; Frede, M.; King, P.; Kracht, D.; Kwee, P. K.; Puncken, O.; Savage, R. L., Jr.; Schulz, B.; Seifert, F.; Veltkamp, C.; Wagner, S.; Weßels, P.; Winkelmann, L.
    Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The...

  8. Demonstration of displacement-noise-free interferometry using bi-directional Mach–Zehnder interferometers

    Sato, S.; Kokeyama, K.; Kawamura, S.; Ward, R. L.; Nishizawa, A.; Chen, Yanbei; Pai, A.; Somiya, K.
    We have demonstrated displacement- and frequency-noise-free laser interferometry (DFI) by partially implementing a recently proposed optical configuration using bi-directional Mach–Zehnder interferometers (MZIs). This partial implementation, the minimum necessary to be called DFI, has confirmed the essential feature of DFI: the combination of two MZI signals can be carried out in a way that cancels the displacement noise of the mirrors and beam splitters while maintaining gravitational-wave signals. The attained maximum displacement noise suppression was 45 dB.

  9. Robust Bayesian detection of unmodelled bursts

    Searle, Antony C.; Sutton, Patrick J.; Tinto, Massimo; Woan, Graham
    We develop a Bayesian treatment of the problem of detecting unmodelled gravitational wave bursts using the new global network of interferometric detectors. We also compare this Bayesian treatment with existing coherent methods, and demonstrate that the existing methods make implicit assumptions on the distribution of signals that make them sub-optimal for realistic signal populations.

  10. Ground-based gravitational-wave detection: now and future

    Whitcomb, Stanley E.
    In the past three years, the first generation of large gravitational-wave interferometers has begun operation near their design sensitivities, taking up the mantle from the bar detectors that pioneered the search for the first direct detection of gravitational waves. Even as the current ground-based interferometers were reaching their design sensitivities, plans were being laid for the future. Advances in technology and lessons learned from the first generation devices have pointed the way to an order of magnitude improvement in sensitivity, as well as expanded frequency ranges and the capability to tailor the sensitivity band to address particular astrophysical sources. Advanced...

  11. Transmission Electron Microscope Studies of LiNi1/3Mn1/3Co1/3O2 before and after Long-Term Aging at 70°C

    Gabrisch, Heike; Yi, Tanghong; Yazami, Rachid
    LiNi1/3Mn1/3Co1/3O2 is a potential cathode material for high-power applications in lithium-ion batteries. While cation ordering on a sqrt(3)×sqrt(3) R30° in-plane superlattice was proposed for the layered structure, the experimental data do not fully support this model. Here, we present a systematic electron diffraction study of LiNi1/3Mn1/3Co1/3O2 in the pristine state and after aging. Our results show that a mixture of different phases in the starting material transforms to the O3-type phase and the cubic spinel phase after aging, accompanied by an increase in the percentage of polycrystals.

  12. Vibrational overtone initiated unimolecular dissociation of HOCH2OOH and HOCD2OOH: Evidence for mode selective behavior

    Matthews, Jamie; Fry, Julie L.; Roehl, Coleen M.; Wennberg, Paul O.; Sinha, Amitabha
    The vibrational overtone induced unimolecular dissociation of HMHP (HOCH2OOH) and HMHP-d2 (HOCD2OOH) into OH and HOCH2O (HOCD2O) fragments is investigated in the region of the 4nuOH and 5nuOH bands. The unimolecular dissociation rates in the threshold region, corresponding to the 4nuOH band, exhibit measurable differences associated with excitation of the OH stretch of the alcohol versus the peroxide functional group, with the higher energy alcohol OH stretching state exhibiting a slower dissociation rate compared to the lower energy peroxide OH stretch in both HMHP and HMHP-d2. Predictions using the Rice–Ramsperger–Kassel–Marcus theory give rates that are in reasonably good agreement with...

  13. Belief propagation algorithm for computing correlation functions in finite-temperature quantum many-body systems on loopy graphs

    Poulin, David; Bilgin, Ersen
    Belief propagation —- a powerful heuristic method to solve inference problems involving a large number of random variables—was recently generalized to quantum theory. Like its classical counterpart, this algorithm is exact on trees when the appropriate independence conditions are met and is expected to provide reliable approximations when operated on loopy graphs. In this paper, we benchmark the performances of loopy quantum belief propagation (QBP) in the context of finite-temperature quantum many-body physics. Our results indicate that QBP provides reliable estimates of the high-temperature correlation function when the typical loop size in the graph is large. As such, it is...

  14. Neurophysiological defects in temperature-sensitive paralytic mutants of Drosophila melanogaster

    Siddiqi, Obaid; Benzer, Seymour
    A new temperature-sensitive paralytic mutant of Drosophila, comatose, is compared behaviorally and physiologically with the previously known types, para and shi. All three have different properties with respect to kinetics of paralysis at high temperature and recovery from paralysis; com is hypersensitive to paralysis by cooling. Neurophysiological experiments indicate different mechanisms for paralysis in each of the mutants.

  15. Models of earth structure inferred from neodymium and strontium isotopic abundances

    Wasserburg, G. J.; DePaolo, D. J.
    A simplified model of earth structure based on the Nd and Sr isotopic characteristics of oceanic and continental tholeiitic flood basalts is presented, taking into account the motion of crustal plates and a chemical balance for trace elements. The resulting structure that is inferred consists of a lower mantle that is still essentially undifferentiated, overlain by an upper mantle that is the residue of the original source from which the continents were derived.

  16. Synthesis of immunoglobulin µ chain gene products precedes synthesis of light chains during B-lymphocyte development

    Siden, E.; Alt, F. W.; Shinefeld, L.; Sato, V.; Baltimore, D.
    Immunoglobulin (Ig) gene expression has been followed during the later stages of development of the murine fetal liver. Biosynthetic labeling and immunoprecipitation were used to isolate Ig-related polypeptides from fetal and neonatal livers. By examination of the specific immune precipitates, the earliest detectable Ig was shown to consist only of µ heavy chain. At about the time of birth, when light chain synthesis became evident, separation of surface Ig-positive cells from surface Ig-negative cells by using anti-Ig-coated dishes showed that cells lacking surface Ig (pre-B lymphocytes) synthesized only µ chains. Thus, commencement of light chain synthesis was closely coordinated with...

  17. Galactic substructure and direct detection of dark matter

    Kamionkowski, Marc; Koushiappas, Savvas M.
    We study the effects of substructure in the Galactic halo on direct detection of dark matter, on searches for energetic neutrinos from weakly interacting massive particles (WIMP) annihilation in the Sun and Earth, and on the enhancement in the WIMP annihilation rate in the halo. Our central result is a probability distribution function (PDF) P(rho) for the local dark-matter density. This distribution must be taken into account when using null dark-matter searches to constrain the properties of dark-matter candidates. We take two approaches to calculating the PDF. The first is an analytic model that capitalizes on the scale-invariant nature of...

  18. Quantum reference frames and deformed symmetries

    Girelli, Florian; Poulin, David
    In the context of constrained quantum mechanics, reference systems are used to construct relational observables that are invariant under the action of the symmetry group. Upon measurement of a relational observable, the reference system undergoes an unavoidable measurement “back-action” that modifies its properties. In a quantum-gravitational setting, it has been argued that such a back-action may produce effects that are described at an effective level as a form of deformed (or doubly) special relativity. We examine this possibility using a simple constrained system that has been extensively studied in the context of quantum information. While our conclusions support the idea...

  19. Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces

    Enami, Shinichi; Hoffmann, M. R.; Colussi, A. J.
    The pulmonary epithelium, like most aerial biosurfaces, is naturally protected against atmospheric ozone (O3) by fluid films that contain ascorbic acid (AH2) and related scavengers. This mechanism of protection will fail, however, if specific copollutants redirect AH2 and O3(g) to produce species that can transduce oxidative damage to underlying tissues. Here, the possibility that the synergistic adverse health effects of atmospheric O3(g) and acidic particulate matter revealed by epidemiological studies could be mediated by hitherto unidentified species is investigated by electrospray mass spectrometry of aqueous AH2 droplets exposed to O3(g). The products of AH2 ozonolysis at the relevant air–water interface...

  20. Numerical Analysis at the National Bureau of Standards

    Todd, John
    In 1946/47, Dr. E. U. Condon (1902–1974), the fourth director of the National Bureau of Standards, arranged for the organization of a Division of Applied Mathematics, under the leadership of Dr. John H. Curtiss. A principal objective of this division was the development of the mathematics appropriate for the automatic digital computing machines then being constructed. An account is given here of some of the activities in numerical analysis carried out by that division in its first 25 years.

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.