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  • Chemistry  (2,113)
  • Cell & Developmental Biology  (205)
  • FLUID MECHANICS AND HEAT TRANSFER  (180)
  • GENERAL
  • 1975-1979  (1,987)
  • 1955-1959  (542)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 1335-1335 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    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: A study has been made of the structure and properties of alternating equimolar and random copolymers of vinylcyclohexanne and α-methylvinylcyclohexane with acrylonitrile using infrared and 1H-NMR spectroscopy methods, as well as x-ray diffraction and differential thermal analyses. The spectral methods allowed an estimation of the composition and distribution of comonomer units in the copolymer macrochains. The thermal stability of alternating copolymers was found to be higher than that of polyacrylonitrile. Alternating and random copolymers are amorphous products with various dimensions of crystallites. Information on the molecular motion intensity and temperatures of structural transitions in copolymer macrochains was obtained by the spin-probe technique.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eine thermische (a) und eine reduktive (b) Methode zur Herstellung von Mikanez-Estern wird beschrieben. Bei der ersten gelang der Nachweis des monomeren Vorläufers, 1,3-Butadien-2-carboxylester. (a)trans/cis-Gemische von Methyl resp. Äthyl 2-Brom-1-methylcyclopropancarboxylat (14/15 resp. 16/17), mit Tri-n-butylzinnhydrid aus den entsprechenden 2,2-Dibrom-1-methylcyclopropancarboxylaten 12 resp. 13 hergestellt, wurden bei 480°/1,7 Torr pyrolysiert. Die bei -78° daraus abgefangenen Kondensate bestanden aus den 1,3-Butadien-2-carboxylaten 5 und 6, im Falle des Äthylesters 6 durch seine 1H-NMR.-Signale charakterisiert und als Addukt (19) mit 4-Phenyl-1,2,4-triazolin-3,5-dion (18) abgefangen (55%). Beim Erwärmen der Kondensate dimerisierten die Dienester 5 resp. 6, so dass sich Dimethyl resp. Diäthyl Mikanezat (9 resp. 10) isolieren liess (67 resp. 100%).(b)Behandlung von Methyl 2(E)-2-Methyl-2-butenoat (20) mit 2 Äquivalenten N-Bromsuccinimid gab (25%) Methyl 2(Z)-4-Brom-2-brommethyl-2-butenoat (21). (Mit 3 Äquivalenten entstand ein Stereomerengemisch 2(Z)- und 2(E)-4,4-Dibrom-2-brommethyl-2-butenoat (22 und 23)). Reduktion des Dibromesters 21 mit Zink in Tetrahydrofuran, Methanol oder Eisessig ergab (50%) Dimethyl Mikanezat (9). Von einer Iodolaktonisierung der aus 9 durch Verseifung hergestellten Mikanezsäure (8) erhielt man 4-Iodo-7-oxo-1-vinyl-6-oxabicyclo[3.2.1]octan-4endo-carbonsäure (24), dessen Bildungsleichtigkeit und IR.-Bande bei 1780 cm eine unabhängige Bestätigung dafür liefert, dass Mikanezsäure (8) durch Kopf-zu-Kopf-Diels-Alder-Dimerisierung von 1,3-Butadien-2-carbonsäure (4) entsteht.Aus Methyl (E)-2-Methyl-2-pentenoat (25) wurde auf gleiche Weise, d.h. über Dibromierung zu 27 und Reduktion mit Zink in Äther, Dimethyl 3,2′-Dimethylmikanezat (29) gewonnen. Die Multiplizität des 1H-NMR.-Signals von H—C(3) in 29 bestätigt, wiederum unabhängig, dass die Dimerisierung des Dienesters (in diesem Fall 28) in Kopf-zu-Kopf-Diels-Alder-Weise stattfindet.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A low-energy spectrometer for the X-ray analysis of plutonium and plutonium-containing materials has been built. We use ultra-thin window to maintain different pressures and contamination level in the spectrometers's sample and crystal chambers. Ultra-thin windows are also used on the X-ray tube and detector. Methods have been developed by which the spectrometer can analyze both metal and loose-powder samples. Representative calibration spectra are presented for the fluorine band in polyfluoroethylene, the oxygen band in α-Al2 O3, and the carbon band in graphite. Experimental spectra are presented for the fluorine band in PuF3 and for the oxygen ban in PuO2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 354-356 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 77Se n.m.r. spectra of twenty-six organoselenium compounds, including some with an endocyclic selenium atom, have been recorded. Our measurements complete the scale of chemical shifts previously established by McFarlane. It seems difficult to define a range of chemical shifts which is characteristic of the valency state of selenium or of its endo- or exocyclic position. Some results are discussed qualitatively. In the case of selenolo[2,3-b]thiophene, evidence has been obtained for a 4J[Se, H] coupling across the sulphur atom.
    Notes: La résonance magnétique du 77Se a été observée dans vingt-six composés organiques dont certains contiennent un atome de sélénium endocyclique. Nous avons pu ainsi compléter l'échelle de déplacements chimiques établie par McFarlane. II apparaît difficile de définir une gamme de déplacement chimique du 77Se caractéristique de son état de valence ou de sa position endo- ou exocyclique. Certains résultats sont discutés qualitativement. Dans le cas du sélénolo [2,3-b]thiophène, des arguments en faveur d'un couplage 4J(Se, H) à travers l'atome de soufre ont été découverts.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 1 (1976), S. 85-89 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The chemical mechanisms for the action of flame retardants are often mentioned in the literature but the physical modes of action are seldom. Discussed. This article presents one way to quantify their efficiency. The technique is based on literature data for the physical and thermal properties of flams retardants for temperatures from 25°C up to 1000°C. The prolongation of the time to ignition by heat absorption by the retardant and the amount of inert gas evolved by the retardant are calculated at a given radiation for a material flame-proofed with a given amount of the flame retardant. The ability to form an insulating surface layer is considered but not quantified. It is assumed that a medium density wood fibre building boards is treated with 2 kg of flame retardant per m2. The flame retardants included are borates, boric acid, phosphates and silicates. The board is assumed to be irradiated with an intensity of 15 k W m-2. Under these conditions an untreated board ignites after 6-7 min. The time to ignition is prolonged by 1-5 min through heat absorption by the different retardants, and the amount of inert gases evolved may be as high as 2.6 m3 per m2 board. The formation of an insulating surface layer is more difficult to quantify. The results confirm the importance of the physical modes of action of flame retardants and the technique could form the basis for evaluating materials in simulated fire situations.
    Additional Material: 1 Ill.
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  • 7
    Publication Date: 2011-08-17
    Description: Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computers and Fluids; 6; June 197
    Format: text
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  • 8
    Publication Date: 2019-06-27
    Description: Results of engineering analyses assessing the conceptual feasibility of a large capacity heat pump for enhancing active cooling of hypersonic aircraft structure are presented. A unique heat pump arrangement which permits cooling the structure of a Mach 6 transport to aluminum temperatures without the aid of thermal shielding is described. The selected concept is compatible with the use of conventional refrigerants, with Freon R-11 selected as the preferred refrigerant. Condenser temperatures were limited to levels compatible with the use of conventional refrigerants by incorporating a unique multipass condenser design, which extracts mechanical energy from the hydrogen fuel, prior to each subsequent pass through the condenser. Results show that it is technically feasible to use a large capacity heat pump in lieu of external shielding. Additional analyses are required to optimally apply this concept.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-145301
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-27
    Description: A combined experimental and computational research program is described for testing and guiding turbulence modeling within regions of separation induced by shock waves incident in turbulent boundary layers. Specifically, studies are made of the separated flow the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include highfrequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-X-73157 , A-6690
    Format: application/pdf
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  • 10
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: New Investigations into Hydrogen Adsorption and Dissolved IronThe solution processes of iron in n HCl were investigated and a correlation was found between the quantity of hydrogen absorbed in the iron and the rate at which the metal dissolved. A dynamical saturation equilibrium was established in the interior of the metal. From this the significance of partial reactions can be derived and the action of inhibitors explained.
    Notes: Es wurden die Auflösungsvorgänge von Eisen in In-HCL untersucht und ein Zusammenhang zwischen der Menge des vom Eisen aufgenommenen Wasserstoffs und der Auflösungsgeschwindigkeit des Metalls gefunden. Es stellt sich dabei ein dynamisches Sättigungsgleichgewicht im Innern des Metalls ein. Daraus läßt sich die Bedeutung der Teil-Reaktionen ableiten und das Eingreifen von Inhibitoren erklären.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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