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  • Computer Systems  (9)
  • Computer Operations and Hardware  (5)
  • Chemistry  (4)
  • Physics
  • 2000-2004  (14)
  • 1965-1969  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Ultrasonic degradation of macromolecules in solution. Study of degradation kinetics by estimation of free-radical scavenger DPPH and solution viscosity measurementsProd. No. 1357 (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1089-1098 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of degradation of butyl rubber in two solvents, cyclohexane and toluene, was studied by two independent techniques: viscosity measurements and free-radical estimation as a function of DPPH consumed. The general shape of the rate curves in the two cases is similar, but not identical. The rate given by estimation of DPPH is faster than that obtained from solution viscosity data. This has been attributed to the inherent limitations of the two methods for the quantitative determination of the number of breaks occurring in the polymer molecules. The rate is also reduced as the viscosity of the solution medium is increased, which may be correlated with the reduction of the cavitation effect responsible for degradation. The degradation rates in two solvent media initially having the same viscosity were unequal. This may be due to different solvent-solute characteristics, which means that the viscosity and cavitation change to different extents in the two cases throughout the course of degradation. The limiting degree of Polymerization (DP)∞ obtained after prolonged irradiation has been found to be dependent on parameters such as intensity of irradiation, solution viscosity, and initial DP of the molecules.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070100801
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Rapid analysis of some coinage, jewellery, aluminium bronze and ternary alloys by the ring oven technique (1965)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 28 (1965), S. 137-140 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Schemes have been worked out for the quantitative separation and subsequent determination of the constituents in a number of alloys containing Au—Cu, Cu—Al, Fe—Au and Fe—Cu—Al by the ring oven technique. Gold is migrated to the ring zone by extraction with n-butanol at pH = 1.5 and iron or copper with acetylacetone. Aluminium is moved to the ring zone by acidified ethanol.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19650280306
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  • 3
    Electronic Resource
    Electronic Resource
    Polymerization of N-vinylearbazole with vanadium compounds. Part I. Polymerization with vanadium pentoxide and metal vanadates (1969)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 124 (1969), S. 263-273 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In Gegenwart von Vanadiumpentoxid als heterogenern Katalysator Wurde N-Vinylcarbazol (NVC) in Substanz polymerisiert. Die Polymerisationsgeschwindigkeit hängt vom Verhältnis des Katalysators zum Monomeren ab. Es wurde ein kationischer Reaktionsmechanismus vorgeschlagen, und es wurde versucht, die Rolle der V2O5-Oberfläche bei der Polymerisation aufzuklären. Es wird vermutet, daß die π-Säureeigenschaft des V5⊕-Ions bei der Initiierung der Polymerisation miteinbezogen werden muß.Die Wirkung einer Anzahl von Zusätzen auf die Polymerisationsgeschwindigkeit wurde untersucht; das Ergebnis bekräftigt die Annahme eines kationischen Verlaufs.Es wurde auch die katalytische Wirksamkeit einer Anzahl von Metallvanadaten bei der Polymerisation von NVC untersucht. Es ergab sich eine hinreichend gute Bezichung zwischen der katalytischen Wirksamkeit und dem elektronegativen Charakter des metallischen Bestandteils.
    Notes: Bulk polymerization of N-Vinylcarbazole (NVC) has been carried out using vanadium pentoxide as the contact catalyst. The rate of polymerizatlon has been found to depend upon catalyst to monomer ratio. A cationic mechanism has been suggested and the role of V2O5 surface in the polymerization has been tentatively analyzed. The π-acid characteristies of V5⊕ ion is believed to be involved in initiating the polymerization. The effect of a number of additives on the polymerization rate has been studied, which endorses the cationic mechanism. The catalytic efficiency of a number of metal vanadates for the polymerization of NVC has also been studied. A fairly good correlation between the activity and electronegativity of the metallic moiety has been established.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1969.021240127
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction of polylysine with phosvitin and nucleic acids (1969)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 124 (1969), S. 113-117 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die DNS-abhängige RNS-Synthese wird durch basische Proteine, wie Histone oder Polylysin, gehmmt: es wurde gefunden, daß dieser Hemmungseffekt durch Phosvitin, ein phosphoprotein, aufgehoben wird. Turbidimetrische Untersuchungen ergaben, daß Polylysin mit DNS iind RNS in stöchiometrischem Verhältnis reagiert.Es wird angenommen, daß diese Reaktion mit DNS die Ursache des Hemmungseffektes ist. Noch wirksamer als DNS reagiert Phosvitin mit Polylysin. Phosvitin kann in viel geringerer als der stöchiometrischen Menge mit DNS um Polylysin konkurrieren, also DNS freisetzen und als Matrize für die RNS-Synthese verfügbar machen. Phosphoserin ist, im Gegensatz zu Phosvitin, unwirksam bei der Aufhebung des Hemmungseffektes von Polylysin.
    Notes: DNA dependent RNA asynthesis in inhibited by basic proteins like histones or polylysine This inhibitory effect is found to be suppressed by phosvitin, which is a phosphoprotein. Turbidometric studies indicate that polylysine interacts with DNA and RNA stoichiometrically. This interaction with DNA has been thought to be the cause of this inhibitory effect. Phovitin also interacts with polylysine more effectively than DNA. Phosvitin in quantities much less than the stoichionietric amount can compete with DNA for the polylysine and can thus make DNA free and available as template for the RNA synthesis. Phosphoserine, unlike pbosvitin, is ineffective in suppressing the inhibitory effect of polylysine.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1969.021240112
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  • 5
    Electronic Resource
    Electronic Resource
    Redox-initiated vinyl polymerization with thiourea as the reductant (1967)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 5 (1967), S. 135-149 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A few redox systems containing thiourea as reductant have been found to be quite effective in initiating vinyl polymerization in aqueous media and polymers obtained in the process have all been found to contain amino endgroups to various extents by the application of dye techniques. Quite a few oxidants have so far been utilized for this purpose; among them are ferric chloride (Fe3+), ethylene dibiguanide complex salts of tripositive silver (Ag3+), hydrogen peroxide (H2O2), persulfate (S2O82-), bromate (BrO3-) + hydrochloric acid (HCl). In case of oxidants Fe3+ and Ag3+, amino endgroups are mainly incorporated in polymers; but in case of oxidants H2O2 and S2O82-, fragments of oxidants are also incorporated as hydroxyl and sulfate endgroups. BrO3-, however, forms a very efficient redox-initiating system with thiourea, as is evidenced by its capability of polymerizing even hydroquinone-stabilized water-soluble vinyl monomers at very low temperature (∼0°C.) and at a quite rapid rate. Besides amino endgroups, sulfonate endgroups have also been detected in polymers in this case, and the relative extents of these two types of endgroups depend generally on the acid concentration of the system. Evidences so far collected indicate the generation of S—C(=NH)NH2 radicals in the system by oxidation of isothiourea, HS—C(=NH)NH2, and these are incorporated in polymers as endgroups. Sulfonate endgroups may be generated by oxidation of these amino-bearing endgroups. Suitable initiation mechanisms have been suggested in each case.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1967.150050112
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  • 6
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    High End Computing Technologies for Earth Science Applications: Trends, Challenges, and Innovations (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Earth science applications of the future will stress the capabilities of even the highest performance supercomputers in the areas of raw compute power, mass storage management, and software environments. These NASA mission critical problems demand usable multi-petaflops and exabyte-scale systems to fully realize their science goals. With an exciting vision of the technologies needed, NASA has established a comprehensive program of advanced research in computer architecture, software tools, and device technology to ensure that, in partnership with US industry, it can meet these demanding requirements with reliable, cost effective, and usable ultra-scale systems. NASA will exploit, explore, and influence emerging high end computing architectures and technologies to accelerate the next generation of engineering, operations, and discovery processes for NASA Enterprises. This article captures this vision and describes the concepts, accomplishments, and the potential payoff of the key thrusts that will help meet the computational challenges in Earth science applications.
    Keywords: Computer Operations and Hardware
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    A Hierarchical and Distributed Approach for Mapping Large Applications to Heterogeneous Grids using Genetic Algorithms (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, we propose a distributed approach for mapping a single large application to a heterogeneous grid environment. To minimize the execution time of the parallel application, we distribute the mapping overhead to the available nodes of the grid. This approach not only provides a fast mapping of tasks to resources but is also scalable. We adopt a hierarchical grid model and accomplish the job of mapping tasks to this topology using a scheduler tree. Results show that our three-phase algorithm provides high quality mappings, and is fast and scalable.
    Keywords: Computer Systems
    Type: IEEE 5th International Conference on Cluster Computing; Dec 01, 2003 - Dec 04, 2003; Hong Kong; China
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Unstructured Adaptive Meshes: Bad for Your Memory? (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This viewgraph presentation explores the need for a NASA Advanced Supercomputing (NAS) parallel benchmark for problems with irregular dynamical memory access. This benchmark is important and necessary because: 1) Problems with localized error source benefit from adaptive nonuniform meshes; 2) Certain machines perform poorly on such problems; 3) Parallel implementation may provide further performance improvement but is difficult. Some examples of problems which use irregular dynamical memory access include: 1) Heat transfer problem; 2) Heat source term; 3) Spectral element method; 4) Base functions; 5) Elemental discrete equations; 6) Global discrete equations. Nonconforming Mesh and Mortar Element Method are covered in greater detail in this presentation.
    Keywords: Computer Operations and Hardware
    Type: ADAPT03: Conference on Adaptive Methods for PDEs and Large-Scale Computation; Oct 11, 2003 - Oct 12, 2003; Troy, NY; United States
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  • 9
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    Ordering Unstructured Meshes for Sparse Matrix Computations on Leading Parallel Systems (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The ability of computers to solve hitherto intractable problems and simulate complex processes using mathematical models makes them an indispensable part of modern science and engineering. Computer simulations of large-scale realistic applications usually require solving a set of non-linear partial differential equations (PDES) over a finite region. For example, one thrust area in the DOE Grand Challenge projects is to design future accelerators such as the SpaHation Neutron Source (SNS). Our colleagues at SLAC need to model complex RFQ cavities with large aspect ratios. Unstructured grids are currently used to resolve the small features in a large computational domain; dynamic mesh adaptation will be added in the future for additional efficiency. The PDEs for electromagnetics are discretized by the FEM method, which leads to a generalized eigenvalue problem Kx = AMx, where K and M are the stiffness and mass matrices, and are very sparse. In a typical cavity model, the number of degrees of freedom is about one million. For such large eigenproblems, direct solution techniques quickly reach the memory limits. Instead, the most widely-used methods are Krylov subspace methods, such as Lanczos or Jacobi-Davidson. In all the Krylov-based algorithms, sparse matrix-vector multiplication (SPMV) must be performed repeatedly. Therefore, the efficiency of SPMV usually determines the eigensolver speed. SPMV is also one of the most heavily used kernels in large-scale numerical simulations.
    Keywords: Computer Systems
    Type: Irregular; May 01, 2000; Cancun; Mexico
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    NASA TECHNICAL REPORTS
  • 10
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    Memory-Intensive Benchmarks: IRAM vs. Cache-Based Machines (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The increasing gap between processor and memory performance has lead to new architectural models for memory-intensive applications. In this paper, we explore the performance of a set of memory-intensive benchmarks and use them to compare the performance of conventional cache-based microprocessors to a mixed logic and DRAM processor called VIRAM. The benchmarks are based on problem statements, rather than specific implementations, and in each case we explore the fundamental hardware requirements of the problem, as well as alternative algorithms and data structures that can help expose fine-grained parallelism or simplify memory access patterns. The benchmarks are characterized by their memory access patterns, their basic control structures, and the ratio of computation to memory operation.
    Keywords: Computer Operations and Hardware
    Type: IPDPS Conference; Apr 15, 2002 - Apr 19, 2002; Fort Lauderdale, FL; United States
    Format: text
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    NASA TECHNICAL REPORTS
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