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1998

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Articles 1 - 30 of 2339

Full-Text Articles in Physical Sciences and Mathematics

Estimating The Usle - Soil Erodibility Factor In Developing Tropical Countries:A Case Study In Tanzania, Metthew Mulengeral Dec 1998

Estimating The Usle - Soil Erodibility Factor In Developing Tropical Countries:A Case Study In Tanzania, Metthew Mulengeral

Tanzania Journal of Engineering and Technology (TJET)

Developing countries in the tropics are facing more soil erosion problems than the developed temperate countries. These developing countries have no accurate locally applicable equation(s) for predicting soil erosion or for planning and implementation of soil conservation measures. Furthermore, These countries do not have the necessary resources to develop the soil loss prediction equation(s). Existing empirical equations like the Universal Soil Loss Equation (USLE) if modified to suit tropical conditions can be useful a tool in soil erosion control in the region for a foreseeable future. In this paper equations'for estimating the soil erodibility factor in the USLE for tropical …

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A Comparison Of Three Numerical Methods Of Solutions Of Equations Describing Unsteady Gas Flow At Pipe Boundaries In Reciprocating Compressor Systems, M Mkumbwa Dec 1998

A Comparison Of Three Numerical Methods Of Solutions Of Equations Describing Unsteady Gas Flow At Pipe Boundaries In Reciprocating Compressor Systems, M Mkumbwa

Tanzania Journal of Engineering and Technology (TJET)

A number of finite difference schemes are available to study pressure fluctuation effects in unsteady pipe flows. This paper presents a comparison Of the predictions made by three such schemes of unsteadyjlow effects in a number of reciprocating compressor pipe-work systems. The finite difference schemes considered were;- a first order scheme known as the method Of characteristics, two second order schemes which were the Leapfrog method and MacCormacVs method. A reciprocating compressor simulation computer program was coupled with equations describing the cylinder thermodynamic processes with the pipe flow equations for steady non-homentropicflow. The comparison presented takes into account both the …

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Electronic Data Interchange : Its Benefits In Trade Activities For Developing Countries, Luis E. Nova [Morel] Dec 1998

Electronic Data Interchange : Its Benefits In Trade Activities For Developing Countries, Luis E. Nova [Morel]

World Maritime University Dissertations

No abstract provided.

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Absorption Efficiencies And Biochemical Fractionation Of Assimilated Compounds In The Cold Water Appendicularian Oikopleura Vanhoeffeni, Alexander B. Bochdansky, Don Deibel, Richard B. Rivkin Dec 1998

Absorption Efficiencies And Biochemical Fractionation Of Assimilated Compounds In The Cold Water Appendicularian Oikopleura Vanhoeffeni, Alexander B. Bochdansky, Don Deibel, Richard B. Rivkin

OES Faculty Publications

Using Ge-68:C-14 dual-labeling, we investigated the absorption efficiency of diatom carbon for the cold water appendicularian Oikopleura vanhoeffeni. The absorption efficiency of bulk carbon (mean = 67%) was not influenced by body size or ingestion rate. For the first time for a pelagic tunicate, food and feces were fractionated into their major biochemical constituents (i.e., low-molecular-weight compounds, lipid, protein, and polysaccharide), allowing calculation of absorption efficiencies for each fraction. Low-molecular-weight compounds and proteins were preferentially absorbed over lipids and polysaccharides. However, predicted C:N ratios of the fecal pellets of O. vanhoeffeni were in the lower range of C:N ratios …

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Turbulent Burning Model For Premixed Gaseous Mixtures, E Mushi Dec 1998

Turbulent Burning Model For Premixed Gaseous Mixtures, E Mushi

Tanzania Journal of Engineering and Technology (TJET)

A turbulent burning model for premixed gaseous mixtures has been successfully developed. The model assumes instant burning of vortex Tubes of the order of Kolmogorov scale followed by burning of larger eddies of the order of Taylor micro scale. These eddies burn ar a rate dependent On the stretch rate. The influence of turbulence on the burning rate is introduced in the form of probability density function which gives the probability that a given mixture under turbulence will undergo burning rather than being quenched. The model has been validated againsi experiments involving turbulent explosions in a fan stirred bomb. Model …

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Extracting Consistent Weight Ratio Matrices From Inconsistent Judgement Matrices., Christian Alphonce Dec 1998

Extracting Consistent Weight Ratio Matrices From Inconsistent Judgement Matrices., Christian Alphonce

Tanzania Journal of Engineering and Technology (TJET)

The Analy,'ic Hierarchy Process (AHP) developed by Saaty Inore (han a decade ago has been widely applied in diverse decision making problenls ranging from socio-economic planning to engineering designs. One of the basic steps of this popular decision support tool is concerned with estimating a ratio scale of a set of entities from their inconsistent pairwise comparison judgement matrix. A number of estimation procedures for this purpose have been proposed. These include Saaty's eigenvector meihod, various geometric means methods, and methods using logarithmic least squares, least squares. and means Transformanons, amongst O,'hers. One Thing conunon to all these Inethods is …

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Analysis Of The Analytic Hierarchy Process Methodologies, C B Alphonce, C M. Brugha Dec 1998

Analysis Of The Analytic Hierarchy Process Methodologies, C B Alphonce, C M. Brugha

Tanzania Journal of Science

We review various methodologies for estimating the impact scores of alternatives on criteria within the Analytic Hierarchy Process (AHP). The results show that the geometric mean method for retrieving impact scores from judgment matrices and the weighted geometric mean aggregation rule provide a best fit to the underlying structure of the problem.

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A Universal Space Group Code In The Natural Science, M E Kamwaya Dec 1998

A Universal Space Group Code In The Natural Science, M E Kamwaya

Tanzania Journal of Science

A more systematic and universal cell-edge rule is proposed, in which the criterion in the determination of space groups (except for the cubic and trigonal systems) should be a ˃ b ˃ c. This leads to having two setting in the tetragonal and hexagonal systems, while in the monoclinic a third setting is added based on when angle a ≠ 90o.

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On Intamolecular Hydrogen Bonding Of O- Hydroxyaromatic Schef Bases And Related Molectules: Structre Of N-P- Chlorobenzylidene -2- Hydroxyaniline, Me Kamwaya Dec 1998

On Intamolecular Hydrogen Bonding Of O- Hydroxyaromatic Schef Bases And Related Molectules: Structre Of N-P- Chlorobenzylidene -2- Hydroxyaniline, Me Kamwaya

Tanzania Journal of Science

C13H10NOCl, Mr = 231.682, F(000) = 480, Z = 4, Dc = 1.387, Dm = 1.385 mgm-3, V = 1109. 53A, is monoclinic, space group P21/n with a = 13.033(4), b = 5.869(7), = 14.77 (4) A, and ß = 78.9(2)0. Least squares refinement led to a final R-value of 0.0539 for 520 reflexions. The presence of a five-membered intramolecular hydrogen bond in N-p-chlorobenzylidene-2-hydroxyaniline is established.

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Ocean Energy : Ocean Thermal Energy Conservation (Otec) As Additional Electricity Source For Nigeria, Haruna Abdu Zailani Dec 1998

Ocean Energy : Ocean Thermal Energy Conservation (Otec) As Additional Electricity Source For Nigeria, Haruna Abdu Zailani

World Maritime University Dissertations

Oceans cover more than 70% of the total surface of the earth and are vast resources of energy. Ocean energy can be retrieved by using adequate ocean energy systems that work on either temperature gradients, salinity gradients, density gradients, the flow of ocean winds, currents, waves, or tidal energy, all of which are renewable. They are never exhausted. The further the ocean energy systems are tested the more prosperous ocean energy becomes. It is certainly the energy for the future, especially when man finishes all the reserves of fossil fuels. Nigeria being the leading African nation, endowed with resources and …

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Heavy Metal Pollution In Lake Victoria, J. W. A. Kandoro, M. H. Mikidadi Dec 1998

Heavy Metal Pollution In Lake Victoria, J. W. A. Kandoro, M. H. Mikidadi

Tanzania Journal of Science

This work presents the Energy dispersive x-ray flouorences (EDXRF) analysis of water and plant samplesfrom Lake Victoria at Mwanza for heavy metal pollution. Water and plant (Water hyacinth) samples were collected from Lake Victoria around Mwanza municipality from twenty seven locations. There were varying elemental concentrations from different locations reflecting the activities carried out in the vicinity of the lake. Maximum concentration values of up to 1640 mg/L for Pb, 23.3 mg/L for Mn, 42.8 mg/L for Cr, 15.1mg/L for Pb, 23.3mg/L for Cu, and 742.5 mg/L for Zn, were observed. Possible sources of the elements are discussed, from which …

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A Person Computer Programme For Fitting Of Moessbauer Spectra, J. W. A. Kandoro Dec 1998

A Person Computer Programme For Fitting Of Moessbauer Spectra, J. W. A. Kandoro

Tanzania Journal of Science

A Computer code for fitting spectra obtained in Moessbauer spectroscopy on a personal computer is described. The code is designed around a least-squares routine which fits the characteristics peaks in a Moessbauer spectrum with Lorentzian shaped peaks and the background of a spectrum with a polynomial function. The least squares routing is based on the Newton-Raphson algorithm. The method is implemented in a computer program written in quick basic for which prove that the program in quick basic for IBM compatible personal computer. Tests are described which prove that the program is able to provide reliable values for the parameters.

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Bottom Reflection In A Shallow Tidal Bay, S B. Mahongo Dec 1998

Bottom Reflection In A Shallow Tidal Bay, S B. Mahongo

Tanzania Journal of Science

Bottom reflection of short-wave radiation was investigated using measurements taken from a platform in a shallow tidal lagoon on the eastern coast of Zanzibar, the Chwaka bay. Measurements were taken from 18 January to 9 February, 1996. The investigation was facilitated using a simple model of shallow water reflectance. The presumption that bottom reflection plays a significant role in the heat budget of the bay has been found to be incorrect. The computed mean value of the flux due to bottom reflection during this period was only of the order of 2Wm-2, and it is unlikely that variations …

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Search For Higgs Bosons Produced In Association With A Vector Boson In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 1998

Search For Higgs Bosons Produced In Association With A Vector Boson In Pp̅ Collisions At √S = 1.8 Tev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We search for Higgs bosons produced in association with a massive vector boson in 91 ± 7 pb-1 of pp̅ collisions at √s =1.8 TeV recorded by the Collider Detector at Fermilab. We assume the Higgs scalar H0 decays to a bb̅ pair with branching ratio β, and we consider the hadronic decays of the vector boson V (W or Z). Observations are consistent with background expectations. We place 95% confidence level upper limits on σ (pp̅→H0V) β as a function of the scalar mass (MH0) …

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Search For The Decays BS0,BD0 → E±Μ± And Pati-Salam Leptoquarks, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 1998

Search For The Decays BS0,BD0 → E±Μ± And Pati-Salam Leptoquarks, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have searched for the decays Bs0→ e±μ± and Bd0 → e±μ± using a 102 pb-1 data sample of pp̅ collisions at √s =1.8 TeV collected with the Collider Detector at Fermilab. We set upper limits on the branching fractions of Ɓ(Bs0 → e±μ±) < 6.1(8.2) X 10-6 and Ɓ(Bd0 → e±μ±) < 3.5(4.5) X 10-6 at 90(95)% confidence level. Using these limits, we set lower bounds on the corresponding Pati-Salam leptoquark masses and find that MLQ(B …

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Density Of Zeros On The Lee-Yang Circle Obtained From Magnetization Data Of A Two-Dimensional Ising Ferromagnet, Christian Binek Dec 1998

Density Of Zeros On The Lee-Yang Circle Obtained From Magnetization Data Of A Two-Dimensional Ising Ferromagnet, Christian Binek

Christian Binek Publications

In order to provide experimental access to the statistical theory of Lee and Yang [Phys. Rev. 87, 410 (1952)] the density function g(θ) of zeros on the Lee-Yang circle has been determined for the first time by analyzing isothermal magnetization data m(H) of the Ising ferromagnet FeCl2 in axial magnetic fields H at temperatures 34≤T≤99 K. The validity of our approach is demonstrated by the perfect agreement of magnetic specific heat data as calculated from g(θ) and m(H) via Maxwell's relation. Moreover, the correct in-plane exchange constant of FeCl2 emerges from the …

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An Ab Initio Study Of The Mono- And Difluorides Of Krypton, Gerald J. Hoffman, Laura A. Swafford '97, Robert J. Cave Dec 1998

An Ab Initio Study Of The Mono- And Difluorides Of Krypton, Gerald J. Hoffman, Laura A. Swafford '97, Robert J. Cave

All HMC Faculty Publications and Research

Results from ab initio calculations at the CCSD(T) level of theory are presented for krypton monofluoride (KrF), krypton monofluoride cation (KrF+), linear, ground-state krypton difluoride (KrF2), the triplet state of krypton difluoride, and the krypton–fluorine van der Waals complex (Kr–F2). These are the first calculations demonstrating that KrF is a bound molecule, in agreement with experimental observation. When corrected for basis-set superposition error, the calculated potential displays quantitative agreement with the attractive wall of the experimentally measured potential curve. Results are also presented for KrF+ and linear KrF2 which yield accurate values for their dissociation energies. The triplet state of …

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Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts Dec 1998

Gravitational Waves From Collapsing Vacuum Domains, Marcelo Gleiser, Ronald Roberts

Dartmouth Scholarship

The breaking of an approximate discrete symmetry, the final stages of a first order phase transition, or a postinflationary biased probability distribution for scalar fields are possible cosmological scenarios characterized by the presence of unstable domain wall networks. Combining analytical and numerical techniques, we show that the nonspherical collapse of these domains can be a powerful source of gravitational waves. We compute their contribution to the stochastic background of gravitational radiation and explore their observability by present and future gravitational wave detectors.

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Fundamental And Magnetic-Hardening Studies Of Nanocrystalline And Naaocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis Dec 1998

Fundamental And Magnetic-Hardening Studies Of Nanocrystalline And Naaocomposite Magnets, David J. Sellmyer, George C. Hadjipanayis

David Sellmyer Publications

In this project we study new nanocrystalline and nanocomposite structures that have high potential for permanent-magnet development. These materials, which can be synthesized to have either very high or intermediate coercivities, have many applications in electric power, transportation, and information-storage industries. There is great interest in further development of understanding and application of these materials. Following are brief discussions of recent research highlights for the present grant.

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Effect Of Temperature On Retention Of Enantiomers Of Β-Methyl Amino Acids On A Teicoplanin Chiral Stationary Phase, Antal Péter, Gabriella Török, Daniel W. Armstrong, Géza Tóth, Dirk Tourwé Dec 1998

Effect Of Temperature On Retention Of Enantiomers Of Β-Methyl Amino Acids On A Teicoplanin Chiral Stationary Phase, Antal Péter, Gabriella Török, Daniel W. Armstrong, Géza Tóth, Dirk Tourwé

Chemistry Faculty Research & Creative Works

The isocratic retention of enantiomers of β-methyl amino acids (β-methyltyrosine, β-methylphenylalanine, β-methyltryptophan and β-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) was studied on a teicoplanin-containing chiral stationary phase at different temperatures and at different mobile phase compositions, using the reversed-phase mode. With variation of both mobile phase composition and temperature, almost baseline separations could be achieved for all four enantiomers of sterically hindered amino acids. The retention factors and selectivity factors for the enantiomers of all investigated compounds decreased with increasing temperature. The natural logarithms of the retention factors (ln k) of the investigated compounds depended linearly on the inverse of temperature (1/T). van 't …

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Experimental Observation Of Relativistic Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter Dec 1998

Experimental Observation Of Relativistic Nonlinear Thomson Scattering, Szu-Yuan Chen, Anatoly Maksimchuk, Donald Umstadter

Donald Umstadter Publications

Classical Thomson scattering—the scattering of low-intensity light by electrons—is a linear process, in that it does not change the frequency of the radiation; moreover, the magnetic-field component of light is not involved. But if the light intensity is extremely high (~1018 Wcm–2), the electrons oscillate during the scattering process with velocities approaching the speed of light. In this relativistic regime, the effect of the magnetic and electric fields on the electron motion should become comparable, and the effective electron mass will increase. Consequently, electrons in such high fields are predicted to quiver nonlinearly, moving in figure-eight patterns …

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Relativistic Nonlinear Optics, Phillip F. Schewe, Ben Stein, Donald P. Umstadter Dec 1998

Relativistic Nonlinear Optics, Phillip F. Schewe, Ben Stein, Donald P. Umstadter

Donald Umstadter Publications

Laser light is a convenient way of transporting both electric and magnetic fields. When an electron encounters light, however, it is usually the electric field that does the talking; the magnetic part of light is less influential since its effect on the electron is proportional to the electron's speed as a fraction of the speed of light (c). In new experiments at the University of Michigan this is all changed since the intensity of the laser light used is so great (a terawatt of power, compared to a milliwatt for a laser in a CD player) that the electrons in …

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On The Basic Representation Theorem For Convex Domination Of Measures, J. Elton, Theodore P. Hill Dec 1998

On The Basic Representation Theorem For Convex Domination Of Measures, J. Elton, Theodore P. Hill

Research Scholars in Residence

A direct, constructive proof is given for the basic representation theorem for convex domination of measures. The proof is given in the finitistic case (purely atomic measures with a finite number of atoms), and a simple argument is then given to extend this result to the general case, including both probability measures and finite Borel measures on infinite-dimensional spaces. The infinite-dimensional case follows quickly from the finite-dimensional case with the use of the approximation property.

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Events With A Rapidity Gap Between Jets In P̅P Collisions At √S = 630 Gev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 1998

Events With A Rapidity Gap Between Jets In P̅P Collisions At √S = 630 Gev, F. Abe, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the fraction of dijet events with a rapidity gap between jets produced by color-singlet exchange in p̅p collisions at √s =630 GeV at the Fermilab Tevatron. In events with two jets of transverse energy ETjet > 8 GeV, pseudorapidity in the range 1.8 <|ηjet | < 3.5 and η1 η2 < 0, the color-singlet exchange fraction is found to be R=[2.7 ± 0.7(stat) ± 0.6(syst)]%. Comparisons are made with results obtained at √s =1800 GeV and with theoretical expectations.

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Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xiii. Ultraviolet Observations Of The Broad-Line Radio Galaxy 3c 390.3, Paul T. O'Brien, M. Dietrich, K. Leighly, D. Alloin, J. Clavel, D. Michael Crenshaw, K. Horne, G. A. Criss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, G. A. Reichert, P. M. Rodriguez-Pascual, W. Wamsteker, K. S.J. Anderson, N. G. Bochkarev, F.-Z. Cheng, A. V. Filippenko, C. Martin Gaskell, I. M. George, M. R. Goad, L. C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, G. Macalpine, D. Marlow, P. G. Martin, S. L. Morris, Richard William Pogge, B. C. Qian, M. C. Recondo-Gonzalez, J. M. Rodriguez Espinosa, M. Santos-Lleo, A. I. Shapovalova, J. M. Shull, G. M. Stirpe, W.-H. Sun, T. J. Turner, R. Vio, S. Wagner, I. Wanders, K. A. Wills, H. Wu, S. J. Xue, Z.-L. Zou Dec 1998

Steps Toward Determination Of The Size And Structure Of The Broad-Line Region In Active Galactic Nuclei. Xiii. Ultraviolet Observations Of The Broad-Line Radio Galaxy 3c 390.3, Paul T. O'Brien, M. Dietrich, K. Leighly, D. Alloin, J. Clavel, D. Michael Crenshaw, K. Horne, G. A. Criss, Julian Henry Krolik, Matthew A. Malkan, Hagai Netzer, Bradley M. Peterson, G. A. Reichert, P. M. Rodriguez-Pascual, W. Wamsteker, K. S.J. Anderson, N. G. Bochkarev, F.-Z. Cheng, A. V. Filippenko, C. Martin Gaskell, I. M. George, M. R. Goad, L. C. Ho, Shai Kaspi, W. Kollatschny, Kirk T. Korista, G. Macalpine, D. Marlow, P. G. Martin, S. L. Morris, Richard William Pogge, B. C. Qian, M. C. Recondo-Gonzalez, J. M. Rodriguez Espinosa, M. Santos-Lleo, A. I. Shapovalova, J. M. Shull, G. M. Stirpe, W.-H. Sun, T. J. Turner, R. Vio, S. Wagner, I. Wanders, K. A. Wills, H. Wu, S. J. Xue, Z.-L. Zou

C. Martin Gaskell Publications

As part of an extensive multi-wavelength monitoring campaign, the International Ultraviolet Explorer satellite was used to observe the broad-line radio galaxy 3C 390.3 during the period 1994 December 31-1996 March 5. Spectra were obtained every 6È10 days. The UV continuum varied by a factor of 7 through the campaign, while the broad emission lines varied by factors of 2È5. Unlike previously monitored Seyfert 1 galaxies, in which the X-ray continuum generally varies with a larger amplitude than the UV, in 3C 390.3 the UV continuum light curve is similar in both amplitude and shape to the X-ray light curve observed …

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Distribution Of Isolated Volcanoes On The Flanks Of The East Pacific Rise, 15.3°-20°S, Scott M. White, Ken C. Macdonald, Daniel S. Scheirer, Marie-Helene Cormier Dec 1998

Distribution Of Isolated Volcanoes On The Flanks Of The East Pacific Rise, 15.3°-20°S, Scott M. White, Ken C. Macdonald, Daniel S. Scheirer, Marie-Helene Cormier

Faculty Publications

Volcanic constructions, not associated with seamount (or volcano) chains, are abundant on the flanks of the East Pacific Rise (EPR) but are rare along the axial high. The distribution of isolated volcanoes, based on multibeam bathymetric maps, is approximately symmetric about the EPR axis. This symmetry contrasts with the asymmetries in the distribution of volcano chains (more abundant on the west flank), the seafloor subsidence rates (slower on the west flank), and the distribution of plate-motion-parallel gravity lineaments (more prominento nthe west flank). Most of the isolated volcanoes complete their growth within -14 km of the axis on crust younger …

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Measurement Of Three-Jet Distributions In Photoproduction At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi Dec 1998

Measurement Of Three-Jet Distributions In Photoproduction At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi

Faculty Publications

The cross section for the photoproduction of events containing three jets with a three-jet invariant mass of M31 > 50 GeV has been measured with the ZEUS detector at HERA. The three-jet angular distributions are inconsistent with a uniform population of the available phase space but are well described by parton shower models and script O sign(α α2s) pQCD calculations. Comparisons with the parton shower model indicate a strong contribution from initial state radiation as well as a sensitivity to the effects of colour coherence. © 1998 Elsevier Science B.V. All rights reserved.

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Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz Dec 1998

Snowflake: Spanning Administrative Domains, Jon Howell, David Kotz

Computer Science Technical Reports

Many distributed systems provide a ``single-system image'' to their users, so the user has the illusion that they are using a single system when in fact they are using many distributed resources. It is a powerful abstraction that helps users to manage the complexity of using distributed resources. The goal of the Snowflake project is to discover how single-system images can be made to span administrative domains. Our current prototype organizes resources in namespaces and distributes them using Java Remote Method Invocation. Challenging issues include how much flexibility should be built into the namespace interface, and how transparent the network …

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Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague Dec 1998

Hey, You Got Your Language In My Operating System!, Jon Howell, Mark Montague

Computer Science Technical Reports

Several projects in the operating systems research community suggest a trend of convergence among features once divided between operating systems and languages. We describe how partial evaluation and transformational programming systems apply to this trend by providing a general framework for application support, from compilation to run-time services. We contend that the community will no longer think of implementing a static collection of services and calling it an operating system; instead, this general framework will allow applications to be flexibly configured, and the ``operating system'' will simply be the application support that is supplied at run-time.

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Static-Electric-Field-Induced, High-Energy Plateau For Scattered X-Ray Photons In Laser-Assisted, X-Ray–Atom Scattering, Dejan B. Miloševic, Anthony F. Starace Dec 1998

Static-Electric-Field-Induced, High-Energy Plateau For Scattered X-Ray Photons In Laser-Assisted, X-Ray–Atom Scattering, Dejan B. Miloševic, Anthony F. Starace

Anthony F. Starace Publications

We consider scattering of x rays by H atoms in the presence of both a linearly polarized laser field and a static electric field. Results for the differential cross section as a function of the number of photons n exchanged with the laser field are presented. For x-ray–atom scattering in the presence of a 1014 W/cm2 laser field the differential cross section has a plateau only for emitted photons (n<0). Adding a static electric field gives rise to an extended plateau for absorbed photons (n>0), indicating a substantial increase of the scattered x-ray energies. We present a quasiclassical explanation of these results.

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