ScholarWorks@UMBC

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Now showing 1 - 20 of 11454

Reproducible and Portable Big Data Analytics in the Cloud
(IEEE, 02-15-2023) Wang, Xin; Guo, Pei; Li, Xingyan; Wang, Jianwu; Gangopadhyay, Aryya; Busart, Carl E.; Freeman, Jade
Cloud computing has become a major approach to help reproduce computational experiments. Yet there are still two main difficulties in reproducing batch based Big Data analytics (including descriptive and predictive analytics) in the cloud. The first is how to automate end-to-end scalable execution of analytics including distributed environment provisioning, analytics pipeline description, parallel execution, and resource termination. The second is that an application developed for one cloud is difficult to be reproduced in another cloud, a.k.a. vendor lock-in problem. To tackle these problems, we leverage serverless computing and containerization techniques for automated scalable execution and reproducibility, and utilize the adapter design pattern to enable application portability and reproducibility across different clouds. We propose and develop an open-source toolkit that supports 1) fully automated end-to-end execution and reproduction via a single command, 2) automated data and configuration storage for each execution, 3) flexible client modes based on user preferences, 4) execution history query, and 5) simple reproduction of existing executions in the same environment or a different environment. We did extensive experiments on both AWS and Azure using four Big Data analytics applications that run on virtual CPU/GPU clusters. The experiments show our toolkit can achieve good execution performance, scalability, and efficient reproducibility for cloud-based Big Data analytics.
Topside Ionosphere of Venus and its Interaction with the Solar Wind
(Nature, 1970-02-07) Bauer, S. J.; Hartle, R. E.; Herman, Jay
THE abrupt termination of the daytime ionosphere of Venus at about 500 km observed with the Mariner V two-frequency occultation experiment provides an extremely interesting picture of the direct interaction of the solar wind with a planetary ionosphere1,2. It has been suggested that a pseudo-magnetopause is formed by magnetic fields carried along by the solar wind and forced to pile up on the topside of the highly conducting planetary ionosphere3,4. This magnetic obstacle then interacts with the superalfvénic and supersonic solar wind to form a bow shock; evidence for such a bow shock has been obtained by experiments on Mariner V and Venera IV (refs. 2 and 5).
Interstellar Cosmic Ray Spectra from the Nonthermal Radio Background from 0.4 to 400 MHz
(APS, 1970-05-25) Goldstein, Melvyn; Ramaty, R.; Fisk, L. A.
We deduce the interstellar electron spectrum from the nonthermal radio background. From 200 MeV to a few GeV the spectral index is 1.8 and there is evidence for residual solar modulation. Above a few GeV, the spectrum is steeper and the intensity is similar to that observed at earth. A consistent modulation for electrons and protons of the same rigidity can be obtained by using the complete diffusion-convection energy-loss theory of solar modulation.
Energy Loss of Cosmic Rays in the Interplanetary Medium
(APS, 1970-09-21) Goldstein, Melvyn; Fisk, L. A.; Ramaty, R.
The expansion of the solar wind is likely to cause low-energy cosmic-ray particles to lose a significant fraction of their energy in the interplanetary medium. It is shown that because of this effect, most of the protons observed below ∼100 MeV and alpha particles below ∼60 MeV/nucleon originate at higher energies, making it impossible to sample directly the interstellar spectra at these energies.
The Theory of Inverse Compton Scattering in a Cold Plasma
(AAS, 1971-02) Goldstein, Melvyn; Lenchek, Allen M.
We have derived a theory for inverse Compton scattering in a cold collisionless plasma. In the absence of a magnetic field, the general shape of the scattered-photon spectrum is qualitatively similar to the vacuum spectrum The average rate of electron-energy loss is three-quarters of the vacuum value if the frequency of the incident photons is close to the plasma frequency In order for the plasma to have a large effect on the scattered-photon spectrum, the incident radiation must propagate below the plasma frequency, which is possible if a magnetic field is present As an example, we use gyrosynchrotron photons propagating in the ordinary mode below the plasma frequency as the source of incident photons When these photons are scattered, the spectrum is greatly suppressed compared with the vacuum results The total scattering cross-section is also sharply decreased in a magnetoactive plasma
The Plasma Physics of the Jovian Decameter Radiation
(AAS, 1972-07) Goldstein, Melvyn; Eviatar, Aharon
We have assumed that the decameter radiation from Jupiter is produced near the local electron gyrofrequency and is amplified as it propagates out of the Jovian magnetosphere. Using the VlasovMaxwell equations, which describe the propagation of radiation in hot collisionless plasmas, we have derived the growth rate for radiation that propagates almost perpendicular to the direction of the magnetic field. When the electrons are described by a loss-cone distribution function, the growth rate is large enough to lead to a large amplification factor over a source region of 100-4000 km, depending on the choice of parameters. Because we expect low-energy electrons to be trapped in the Jovian dipole field regardless of the position of the satellite lo, we maintain that this model provides a plausible mechanism for the decametric radiation not associated with lo.
Modulation of Low Energy Galactic Electrons
(1973) Fisk, L. A.; Forman, M. A.; Goldstein, Melvyn
Turbulent Heating of Colliding Streams in the Solar Wind
(AAS, 1973-01) Goldstein, Melvyn; Eviatar, Aharon
Turbulent heating of colliding plasma streams has previously been observed in the solar wind. The original data were interpreted in terms of a fluid model. We argue that a plasma-kinctic description is the more appropriate theoretical approach and is necessary in order to better understand the microscopic physical phenomena that underlie all fluid models. We used microscopic solar-wind parameters characteristic of conditions during the observations, together with the quasi-linear plasma-kinetic theory, to compute the expected magnetic field and temperature enhancements in the interaction region between two counterstreaming plasma beams. The physical mechanism of excitation is the electromagnetic two-stream instability in which Alfve'n waves are unstable. We compute a total field in the interaction region of B ∼ 8 γ (10-12 γ is observed) and a change in temperature of ΔT ∼ 1 x 10⁵ ° K is observed). Other features of the observations are discussed in terms of a plasma-kinetic theory.
On the theory of large amplitude Alfven waves
(NTRS, 1974-04-01) Goldstein, Melvyn; Klimas, A. J.; Barish, F. D.
Large amplitude Alfvenic disturbances of arbitrary spatial shape and polarization are described by MHD equations, without resort to the usual assumption of planarity. However, because of their nonplanar nature, the direction of propagation of these disturbances cannot, in general, be determined by looking for minima in a variance matrix constructed from observed field fluctuations. When such minima exist, one is observing that subset of interplanetary Alfven waves that is essentially planar.
Stabilization of Electron Streams in Type III Solar Radio Bursts
(AAS, 1974-05) Papadopoulos, Konstantinos; Goldstein, Melvyn; Smith, Robert A.
We show that the electron streams that give rise to type III solar radio bursts are stable and will not be decelerated while propagating out of the solar corona. The stabilization mechanism depends on the parametric oscillating two-stream instability. Radiation is produced near the fundamental and second harmonic of the local electron plasma frequency. Estimates of the emission at the second harmonic indicate that the wave spectra created by the oscillating two-stream instability can account for the observed intensities of type III bursts. Subject headings: corona, solar - plasmas - radio radiation, solar
The Fokker-Planck Coefficient for Pitch-Angle Scattering of Cosmic Rays
(AAS, 1974-06) Fisk, L. A.; Goldstein, Melvyn; Klimas, A. J.; Sandri, G.
For the case of homogeneous, isotropic magnetic field fluctuations, it is shown that most theories which are based on the quasi-linear and adiabatic approximations yield the same integral for the Fokker-Planck coefficient for the pitch-angle scattering of cosmic rays. For example, despite apparent differences, the theories due to Jokipii and to Klimas and Sandri yield the same integral. It is also shown, however, that this integral in most cases has been evaluated incorrectly in the past. For small pitch angles, the errors in previous evaluations are fortuitously of minor importance. For large pitch angles, however, these errors become more significant; and for pitch angles of 900, the actual Fokker-Planck coefficient contains a delta-function which has been overlooked in the past. The implications of these corrections on our ability to relate cosmic-ray diffusion coefficients to observed properties of the interplanetary magnetic field are discussed.
Specialized transducing phages for ribosomal protein genes of Escherichia coli
(National Academy of Sciences, 1975-01-01) Jaskunas, S. R.; Lindahl, L.; Nomura, M.
Specialized lambda transducing phages have been isolated carrying approximately half the ribosomal protein genes of E. coli. These phages carry regions of the bacterial chromosome between aroE and fus. The ribosomal protein genes on these phages have been identified by the stimulation of ribosomal protein synthesis in ultraviolet-irradiated bacteria following infection by the transducing phage, and by the in vitro synthesis of ribosomal proteins in a DNA-dependent protein synthesizing system. The results indicate lambdadspcl probably carries at least 22 ribosomal protein genes and lambdadspc2 at least 26 genes. All these genes are clustered between trkA and strA. At least 13 of them have not been previously mapped.
Mirroring in the Fokker-Planck coefficient for cosmic-ray pitch-angle scattering in homogeneous magnetic turbulence
(AAS, 1975-02) Goldstein, Melvyn; Klimas, A. J.; Sandri, G.
The Fokker-Planck coefficient for pitch-angle scattering, appropriate for cosmic rays in homogeneous stationary magnetic turbulence is computed without making any specific assumptions concerning the statistical symmetries of the random field. The Fokker-Planck coefficient obtained can be used to compute the parallel diffusion coefficient for high-energy cosmic rays propagating in the presence of strong turbulence, or for low-energy cosmic rays in the presence of weak turbulence. Because of the generality of magnetic turbulence allowed for in the analysis, special interplanetary magnetic field features, such as discontinuities or particular wave modes, can be included rigorously.
Cluster of genes in Escherichia coli for ribosomal proteins, ribosomal RNA, and RNA polymerase subunits
(National Academy of Sciences, 1975-07-01) Lindahl, L.; Jaskunas, S. R.; Dennis, P. P.; Nomura, M.
This work was supported in part by the College of Agriculture and Life Sciences, University of Wisconsin, and by grants from the National Science Foundation (GB31086) and the National Institute of General Medical Sciences (GM-20427). L.L. is a recipient of a Postdoctoral fellowship from the European Molecular Biology Organization.
Lunar magnetism
(Nature, 1975-11-13) Goldstein, Melvyn
On the theory of the type III burst exciter
(Springer Nature, 1976-02) Smith, Robert A.; Goldstein, Melvyn; Papadopoulos, Konstantinos
In situ satellite observations of type III burst exciters at 1 AU show that the beam does not evolve into a plateau in velocity space, contrary to the prediction quasilinear theory. The observations can be explained by a theory that includes mode coupling effects due to excitation of the parametric oscillating two-stream instability and its saturation by anomalous resistivity. The time evolution of the beam velocity distribution is included in the analysis.
A nonlinear theory of cosmic-ray pitch-angle diffusion in homogeneous magnetostatic turbulence
(AAS, 1976-03) Goldstein, Melvyn
A plasma strong turbulence, weak coupling, theory is applied to the problem of cosmic-ray pitch-angle scattering in magnetostatic turbulence. The theory used is a rigorous generalization of Weinstock's 'resonance broadening' theory and contains no ad hoc approximations. A detailed calculation is presented for a model of 'slab' turbulence with an exponential correlation function. The results agree well with numerical simulations. The rigidity dependence of the pitch-angle scattering coefficient differs from that found by previous researchers. The differences result from an inadequate treatment of particle trajectories near 90 deg pitch angle in earlier work.
Consequences of using nonlinear particle trajectories to compute spatial diffusion coefficients
(NTRS, 1976-09-01) Goldstein, Melvyn
The propagation of charged particles through interstellar and interplanetary space has often been described as a random process in which the particles are scattered by ambient electromagnetic turbulence. In general, this changes both the magnitude and direction of the particles' momentum. Some situations for which scattering in direction (pitch angle) is of primary interest were studied. A perturbed orbit, resonant scattering theory for pitch-angle diffusion in magnetostatic turbulence was slightly generalized and then utilized to compute the diffusion coefficient for spatial propagation parallel to the mean magnetic field, Kappa. All divergences inherent in the quasilinear formalism when the power spectrum of the fluctuation field falls off as K to the minus Q power (Q less than 2) were removed. Various methods of computing Kappa were compared and limits on the validity of the theory discussed. For Q less than 1 or 2, the various methods give roughly comparable values of Kappa, but use of perturbed orbits systematically results in a somewhat smaller Kappa than can be obtained from quasilinear theory.
Involuntary Community: Conscientious Objectors at Patapsco State Park During World War II
(Maryland Center for History and Culture, 1977) Orser, W. Edward
IN MAY 1941 TWENTY-SIX IDEALISTS RETREATED INTO THE WOODS OF PATAPSCO State Park near Baltimore to form a community of pacifists in a nation on the verge of war. While the camp they established resembled many experiments in intentional community, these men were conscientious objectors who had been assigned as draftees under the Selective Service Act of 1940 to do "work of national importance under civilian direction." The Patapsco camp, the first for conscientious objectors in American history, lasted for slightly over one year until it was transferred to the Maryland Eastern Shore in August 1942. By that time the Civilian Public Service system was in full operation, with other camps spread throughout the country. For its one year of existence the Patapsco camp (C.P.S. #3) represented an unusual experiment in cooperative pacifist living and service within the context of wartime compulsory service, a fascinating instance of involuntary community.
Mapping of ribosomal protein genes by in vitro protein synthesis using DNA fragments of lambda fus3 transducing phage DNA as templates
(1977-10-25) Lindahl, Lasse; Post, Leonard; Zengel, Janice; Gilbert, Scott F.; Strycharz, William A.; Nomura, Masayasu
hfus3 (or hfus2) transducing phage stimulates the synthesis of 27 ribosomal proteins, elongation factors EF-Tu and EF-G, and RNA polymerase subunit (Y in ultraviolet-irradiated Escherichia roli cells (see a preceding paper, Jaskunas, S. R., Fallon, A. M., and Nomura M. (1977) .I. Bid. Chem. 252, 7323-7336). The presence of the structural genes for these proteins on the hfus3 genome was proven by demonstrating the synthesis of these proteins in a DNA-dependent protein-synthesizing system using Afus3 DNA, or its restriction enzyme fragments, or both, as template. Proteins synthesized in the system were identified by a combination of techniques. including gel electrophoresis, immunochemical reactions, and tryptic peptide analysis. Restriction endonuclease-sensitive sites on kfus3 DNA were mapped, and genes were located using restriction endonuclease fragments of Afus3 DNA, isolated directly or cloned in phage or plasmid vectors, as templates for protein synthesis. Additional information about the locations of the genes was obtained using DNA from insertion and deletion mutants of hfux3. The results obtained in these in oilro experiments (rf. Fig. 2), and those obtained in the in uiuo experiments from preceding papers in this series, are in excellent agreement and map the essential genes on Afun and their promoters as follows (going counter-clockwise on the E. coli chromosome): R,,.. (S12, S7), EF-G, EF-Tu; k,,), SlO, LB, (1~4. L2. L23), (L22. S19), s3, (S17, L16, L29); hUC, L14, L34, L5, S14, S8, L6, LlR, S5, (130, L15); pa, S13, Sll, S4, IY, L17. Re-examination of the results of previous physiological experiments (Dennis, P. P. (1974) J. Mol. Biol. 89, 223- 232) using the present information on r-protein gene organization demonstrates that the increase in the differential synthesis rate of ribosomal proteins during the transition period following the nutritional shift-up is primarily due to the increase in the frequency of initiation of the transcription of ribosomal protein genes.

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