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Caltech Authors (91,796 recursos)
Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 40,443

1. Relationship between seismicity and geologic structure in western Japan - Allen, Clarence R.; Matsuda, Tokihiko; Okada, Atsumasa
Most large on-shore shallow earthquakes in western Japan have been associated with faults having a previous history of Quaternary displacements. However, the number of such Quaternary faults is very great and their average length is short, so that identification of the most active and dangerous faults is more difficult than in areas such as California or New Zealand that are dominated by obvious master faults. Physiographic features of Quaternary faulting are far more abundant in western Japan than has usually been thought by geologists. Difficulty in recognition has been caused by heavy vegetation, a long history of agricultural modifications, recent volcanism, and numerous massive landslides. The most active-appearing faults...

2. Considerations for design of source apportionment studies - Gordon, Glen E.; Pierson, William R.; Daisey, Joan M.; Lioy, Paul J.; Cooper, John A.; Watson, John G., Jr.; Cass, Glen R.
This report recommends procedures for source and ambient sampling and analysis in source apportionment studies. The recommendations are based on the results of receptor model studies of atmospheric particles in urban areas, especially a recent study of Houston, TX, undertaken as part of the Mathematical and Empirical Receptor Models Workshop (Quail Roost II). The recommendations are presented at three levels of increasing cost and detail of information obtained. Existing mass emissions inventories combined with chemically resolved test data from similar sources (not necessarily in the same locale) can be used to initially estimate the sources of elements present on ambient...

3. Fixation of Nitrogen in the Prebiotic Atmosphere - Yung, Y. L.; McElroy, M. B.
Reactions between nitrogen and water in the air surrounding lightning discharges can provide an important source of nitric oxide even under conditions where oxygen is a minor atmospheric constituent. Estimates are given for the associated source of soluble nitrite and nitrate. It is shown that lightning and subsequent atmospheric chemistry can provide a source of nitrate for the primitive ocean as large as 106 tons of nitrogen per year, sufficient to fill the ocean to its present level of nitrate in less than 10^6 years.

4. Evidence for primary aragonite precipitation, lower Proterozoic (1.9 Ga) Rocknest dolomite, Wopmay orogen, northwest Canada - Grotzinger, J. P.; Reed, J. F.
Abundant precipitation of aragonite is suggested by well-preserved fabrics in dolostones of the lower Proterozoic (1.9 Ga) Rocknest Formation. Fabrics include dolomite and silica after botryoidal aragonite in tepee structures and seafloor cement fans, and cement crusts in cryptalgal tufas. Aragonite was common on the 1.9-Ga Rocknest shelf, as it is on modern tropical shelves. A search for similar marine cement fabrics in other Precambrian carbonates should help resolve whether aragonite was an important precipitate from Precambrian tropical seas (implying an ocean carbonate chemistry similar to today), or if aragonite precipitation was restricted to rare times in the past, calcite...

5. Particle Wall Loss Rates in Vessels - Crump, James G.; Flagan, Richard C.; Seinfeld, John H.
Aerosol particle wall loss rates were determined experimentally in a spherical continuous stirred tank reactor. Tbe particle size and mixing rate dependences are shown to agree with β=12k_eD/Rπvʃ^nv/2√k_2D_0 te^t/e^t-1dt+v/4R3 the theoretical result of Crump and Seinfeld, in which the particle loss coefficient β is related to particle diffusivity D, particle settling velocity r, the coefficient of the eddy diffusivity k_e, and vessel radius R. For the vessel used in these experiments, k_e was found to be proportional to the 3/2 power of the volumetric now rate, in accordance with theoretical expectations. Results of a similar nature may be expected to hold in vessels of...

6. An experimental study of the oxidation of sulfur dioxide in aqueous manganese sulfate aerosols - Crump, James G.; Flagan, Richard C.; Seinfeld, John H.
A continuous stirred tank reactor is used to study growth of manganese sulfate (MnSO_4) aerosols due to catalytic oxidation of SO_2 in humid air. Humidities ranged from 91–97% and SO_2 concentrations from 0 to 92 ppm. The results of the growth studies are consistent with the rate expression for production of sulfuric acid: d[H_2SO_4]/dt=(8.3±2.5)x10^(-5)/[H^+]Ms^(-1). This expression is estimated to hold for [Mn^(2+)] ⩾ 0.O1 M and [SO_2] ⩾ 10 ppm.

7. Sodium Emission from Io: Implications - McElroy, Michael B.; Yung, Yuk Ling; Brown, Robert A.
The surface of lo may be covered with a layer of ammonia ice containing trace amounts of sodium potassium, and calcium; and atmospheric nitrogen could be formed as a photochemical product of ammonia photolysis. Intense sporadic sodium emission from Io can be excited by collisions involving vibrationally excited nitrogen molecules. These metastable molecules may be formed by electron impact, with electrons energized by an auroral mechanism. In order to account for the intensity ratio of the sodium doublet, it is necessary to invoke scattering in a thick gaseous envelope ejected by Io.

8. Further Results on Inversion of Aerosol Size Distribution Data: Higher-Order Sobolev Spaces and Constraints - Crump, James G.; Seinfeld, John H.
The aerosol size distribution inversion algorithm of Crump and Seinfeld, based on the concept of regularization with generalized cross-validation, is extended to Sobolev spaces of order m. The use of the cross-validation function for choice of an appropriate value of m in a particular application is discussed. An inversion algorithm that constrains the size distribution to be nonnegative is introduced and shown to be of value for sharply peaked distributions.

9. Search for Jovian auroral hot spots - Atreya, S. K.; Yung, Y. L.; Donahue, T. M.; Barker, E. S.
Auroral emission originating at the foot of the Io-associated flux tube at Jupiter has been detected with a high-resolution spectrometer/telescope on board the Orbiting Astronomical Observatory Copernicus. The emission intensity at Ly-alpha is found to be greater than 100 kR, and the emission is located at zenographic latitudes greater than 65°.

10. Thermodynamic prediction of the water activity, NH_4NO_3 dissociation constant, density and refractive index for the NH_4NO_3-(NH_4)_2SO_4-H_2O system at 25°C - Stelson, A. W.; Seinfeld, J. H.
The thermodynamic properties, water activity, density and refractive index of NH_4NO_3-(NH_4)_2SO_4-H_2O aerosols are estimated from binary solution data and existing mixing rules. Particle growth is shown to be predictable from the particle composition, the NH_4NO_3-(NH_4)_2SO_4-H_2O phase diagram and the water activity calculation technique of C.L. Kusik and H.P. Meissner (1978, A.I.Ch. E. Symp. 173, 14–20). Good agreement between the theoretical predictions and the experimental measurements of I.N. Tang et al. (1981, Atmospheric Environment15, 2463–2471), J. Thudium (1978,Pageoph. 116, 130–148) and H.H. Emons and W. Hahn (1970, Wiss Z.12, 129–132) is shown. Also, the effect of (NH_4)_2SO_4 on the relative humidity...

11. Seismological investigations - Allen, Clarence R.
The San Fernando earthquake of 9 February 1971, now assigned a magnitude of 6.4 by the Pasadena Network, occurred in an area of low to moderate seismic activity in the years preceding 1971. There were no known reasons to suspect a major earthquake in this area more than in many other geologically and seismologically similar areas in Southern California, and there were no recognized events precursory to the main shock. It is assigned an epicenter at 34°24.7 min. N., 118°24.0 min. W., and a depth of about 8 1/2 km. The seismic and geologic field data are in good agreement in pointing to a major N-dipping thrust fault...

12. Collision efficiencies of diffusing spherical particles: hydrodynamic, van der Waals and electrostatic forces - Valioulis, Iraklis A.; List, E. John
A practical limitation of the application of Smoluchowski's classical estimate for the collisions probability of two diffusing spherical particles in Brownian motion is the non-consideration of interparticle forcves. For suspended particles in water such forces can arise from the disturbance the particle causes in the fluid (hydrodynamic forces), from the cloud of ions which surround an electrically charged particle (double layer forces) or they can be of molecular origin (van der Waals forces). In this paper corrections to Smoluckhowski's collision probability are computed when such forces operate Scoluchowski's collision probability are computed when such forces operate between two approaching particles...

13. The Nitrogen Cycle: Perturbations Due to Man and Their Impact on Atmospheric N_2O and O_3 - McElroy, M. B.; Wofsy, S. C.; Yung, Y. L.
Features of the global cycle of fixed nitrogen are reviewed with an emphasis on perturbations due to man. It is argued that agricultural practices and combustion may lead to an increase in the concentration of atmospheric N2_O with consequent effects on O_3. The level of O_3 may drop by about 20% over the next 100 years if world population and the demand for food should continue to grow at anything like rates which prevailed in the recent past. Uncertainties in the model are highlighted and note is taken of areas where there is need for additional data.

14. Numerical Simulation of a Sedimentation Basin. 1. Model Development - Valioulis, Iraklis A.; List, E. John
A method for the numerical simulation of a rectangular sedimentation basin operating under steady or unsteady conditions is described. The computer model follows the spatial and temporal development of the influent particle size distribution toward the outlet of the tank. It is based on the fundamental mechanisms which govern particle motion and growth. The model accounts for the variability of the flow field and the particle size distribution in the tank and, from the local development of the particle size spectrum, predicts the overall performance of the settling basin.

15. Monte Carlo simulation of coagulation in discrete particle-size distributions. Part 2. Interparticle forces and the quasi-stationary equilibrium hypothesis - Valioulis, I. A.; List, E. J.; Pearson, H. J.
Hunt (1982) and Friedlander (1960a, b) used dimensional analysis to derive expressions for the steady-state particle-size distribution in aerosols and hydrosols. Their results were supported by the Monte Carlo simulation of a non-interacting coagulating population of suspended spherical particles developed by Pearson, Valioulis & List (1984). Here the realism of the Monte Carlo simulation is improved by accounting for the modification to the coagulation rate caused by van der Waals', electrostatic and hydrodynamic forces acting between particles. The results indicate that the major hypothesis underlying the dimensional reasoning, that is, collisions between particles of similar size are most important in...

16. Primitive atmosphere and implications for the formation of channels on Mars - Yung, Y. L.; Pinto, J. P.
The channels on Mars suggest that a flowing fluid has been present on the surface of the planet. It seems natural to assume that this fluid was water. The major difficulty, however, is that water freezes in climatic conditions like those now on Mars. It has been suggested that primitive Mars had a reducing atmosphere, composed mainly of methane. Such an atmosphere, as we show here, could be polymerised by solar ultraviolet radiation to produce higher hydrocarbons. These compounds are low viscosity liquids at today's temperature on Mars, and could contribute to the formation of channels.

17. Isotopic Composition of Nitrogen: Implications for the Past History of Mars' Atmosphere - McElroy, Michael B.; Yung, Yuk Ling; Nier, Alfred O.
Models are presented for the past history of nitrogen on Mars based on Viking measurements showing that the atmosphere is enriched in ^(15)N. The enrichment is attributed to selective escape, with fast atoms formed in the exosphere by electron impact dissociation of N_2 and by dissociative recombination of N_2+. The initial partial pressure of N_2 should have been at least as large as several millibars and could have been as large as 30 millibars if surface processes were to represent an important sink for atmospheric HNO_2 and HNO_3.

18. Sulfate accumulation in a sea breeze/land breeze circulation system - Cass, Glen R.; Shair, Frederick H.
An atmospheric tracer study using SF_6 was conducted on July 22, 1977, to examine the origin of the high particulate sulfate concentrations observed in coastal Los Angeles County. It was found that the sea breeze/land breeze circulation system in the Los Angeles Basin both increases the retention time for sulfate formation in the marine environment and causes individual air parcels to make multiple passes over large coastal emissions sources. Day-old sulfur oxides emissions advected out to sea by the land breeze at night were estimated to be the largest single contributor to 24-hour average sulfate air quality over land the...

19. Ozone and the deterioration of works of art - Shaver, Cynthia L.; Cass, Glen R.; Druzik, James R.
Seventeen artists' watercolor pigment samples and two Japanese woodblock prints were exposed to 0.40 ppm ozone in a controlled test chamber for three months. It was found that several artists' pigments when applied on paper will fade in the absence of light if exposed to an atmosphere containing ozone at the concentrations found in photochemical smog. Alizarin-based watercolors containing 1,2 dihydroxyanthraquinone lake pigments were shown to be particularly sensitive to ozone damage, as were the yellow pigments used in the Japanese woodblock prints tested. Indoor-outdoor ozone monitoring in a Pasadena, CA art gallery confirmed that ozone concentrations half as high as...

20. Aerosols from a Laboratory Pulverized Coal Combustor - Taylor, D. D.; Flagan, R. C.
A laboratory study has been undertaken to characterize the aerosol produced during pulverized coal combustion. The emphasis in this work has been on the particulate matter present in the flue gases at the inlet to the gas cleaning equipment rather than that leaving the stack. Coal is burned at conditions which simulate the combustion region of coal-fired utility boilers. The combustion products then pass through a series of convective heat exchangers which cool them to normal flue gas temperature. Samples extracted from the cool (400-500°K) combustion products are analyzed for major gaseous products and aerosol properties. The size distribution of...

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