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  • ELECTRONICS AND ELECTRICAL ENGINEERING  (4)
  • Polymer and Materials Science  (3)
  • Electron microscopy  (1)
  • 1
    ISSN: 1432-072X
    Keywords: Bradyrhizobium ; Electron microscopy ; Mutants ; Nitrogen fixation ; Nodulation ; Soybean ; Symbiosis ; Transposon Tn5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genome of the slow-growing Bradyrhizobium japonicum (strain 110) was mutagenized with transposon Tn5. A total of 1623 kanamycin/streptomycin resistant derivatives were screened in soybean infection tests for nodulation (Nod) and symbiotic nitrogen fixation (Fix). In this report we describe 14 strains possessing a stable, reproducible Nod+Fix- phenotype. These strains were also grown under microaerobic culture conditions to test them for free-living nitrogen fixation activity (Nif). In addition to strains having reduced Fix and Nif activities, there were also strains that had reduced symbiotic Fix activity but were Nif+ ex planta. Analysis of the genomic structure revealed that the majority of the strains had a single Tn5 insertion without any further apparent physical alteration. A few strains had additional insertions (by Tn5 or IS50), or a deletion, or had cointegrated part of the vector used for Tn5 mutagenesis. One of the insertions was found in a known nif gene (nifD) whereas all other mutations seem to affect different, hitherto unknown genes or operons. Several mutant strains had an altered nodulation phenotype, inducing numerous, small, widely distributed nodules. Light and electron microscopy revealed that most of these mutants were defective in different stages of bacteroid development and/or bacteroid persistence. The protein patterns of the mutants were inspected by two-dimensional gel electrophoresis after labelling microaerobic cultures with l-(35S)methionine. Of particular interest were mutants lacking a group of proteins the synthesis of which was known to be under oxygen control. Such strains can be regarded as potential regulatory mutants.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 42 (1960), S. 35-48 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular weight distributions have been found for fractions of polystyrene degraded ultrasonically in benzene solution at very low concentrations (0.002% w/v). The distributions show that little, if any, of the degradation products include molecules of molecular weight less than 50,000. The variation of the rate constant for the degradation of the molecules with molecular weight follows the theoretical relation being proportional to M2.82 derived in Part I up to molecular weights of 106. Beyond this value the rate constant increases at a slower rate. This is attributed to a change in the variation of the shock pressure and rear flank of the shock wave with distance from the cavity. The rate constant for a given fraction reaches a peak at a concentration of about 0.01% w/v after which it falls rapidly with increasing concentration. This is attributed to the formation of a network by the polymer which reduces the rate of the cavity collapse.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 36 (1959), S. 173-182 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reactivity ratios in the copolymerization of methacrylonitrile with styrene, methacrylic acid, and eleven alkyl methacrylates have been determined and the Alfrey-Price Q and e values calculated. Monomer reactivity in these systems is principally a function of resonance stabilization (Q), polar factors (e) playing a relatively minor role. With the exception of the stearyl ester, the changes in the Q and e values which occur on ascending the homologous series can be accounted for qualitatively in terms of the expected relative electronic displacements and of the steric effects caused by the various alkyl groups. Some correlation between monomer reactivity and the depolymerizability of the corresponding polymer has been noted.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 2 (1964), S. 2875-2882 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some graft copolymerizations of monomers with substrates previously irradiated in air to form polymeric peroxides have been studied at pressures up to 8000 atm. In the heterogeneous system styrene-irradiated polyethylene, the rate of grafting increases considerably with pressure up to about 3000 atm. At higher pressures the reaction is retarded, and this is attributed to diffusion control of the propagation reaction. The rate of homopolymerization increases exponentially with pressure over the range 1-4000 atm. Irreproducible results were obtained when methyl methacrylate was used in place of styrene, possibly because the substrate is not swollen by this monomer. No grafting was observed between five different chloro-substituted ethylenes and irradiated polyethylene at pressures up to 5000 atm. The rate of grafting in the homogeneous system vinyl acetate-irradiated polystyrene increases considerably with pressure up to 8000 atm., and there is no indication of diffusion control of the propagation reaction.
    Additional Material: 2 Ill.
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  • 5
    Publication Date: 2011-08-19
    Description: The use of the alpha-Ge(1-x):Al(x) and alpha-Ge(1-x):Cu(x) alloys and Pt/Al2O3 cermet thin films as resistive interconnects for binary synaptic memory arrays is evaluated. The fabrication of the 10-20 microns long, 10 microns wide, and 0.1 micron thick interconnects from the alloys and cermet is described. The current-voltage and switching characteristics of the as-deposited films and the patterned test structure are studied. The resistivity, uniformity, stability, and compatibility of the interconnects are examined. It is observed that alpha-Ge(1-x):Cu(x) alloys have a wide resistivity range and low temperature coefficients of resistance; however, their long-term stability is limited due to their low crystallization temperature. It is detected that the alpha-Ge(1-x):Al(x) alloys have higher crystallization temperatures and their resistivity is not greatly affected by large changes in metal content. The Pt/Al2O3 samples display excellent stability, easy fabrication, and control of resistivity with metal content.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 5; 1407-141
    Format: text
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  • 6
    Publication Date: 2011-08-19
    Description: Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Applied Electrochemistry (ISSN 0021-891X); 18; 410-416
    Format: text
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  • 7
    Publication Date: 2011-08-19
    Description: A scheme for nonvolatile associative electronic memory storage with high information storage density is proposed which is based on neural network models and which uses a matrix of two-terminal passive interconnections (synapses). It is noted that the massive parallelism in the architecture would require the ON state of a synaptic connection to be unusually weak (highly resistive). Memory switching using a-Si:H along with ballast resistors patterned from amorphous Ge-metal alloys is investigated for a binary programmable read only memory matrix. The fabrication of a 1600 synapse test array of uniform connection strengths and a-Si:H switching elements is discussed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 8
    Publication Date: 2019-07-13
    Description: A novel thin film approach to neural-network-based high-density associative memory is described. The information is stored locally in a memory matrix of passive, nonvolatile, binary connection elements with a potential to achieve a storage density of 10 to the 9th bits/sq cm. Microswitches based on memory switching in thin film hydrogenated amorphous silicon, and alternatively in manganese oxide, have been used as programmable read-only memory elements. Low-energy switching has been ascertained in both these materials. Fabrication and testing of memory matrix is described. High-speed associative recall approaching 10 to the 7th bits/sec and high storage capacity in such a connection matrix memory system is also described.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEDM - International Electron Devices Meeting; Dec 06, 1987 - Dec 09, 1987; Washington, DC; United States
    Format: text
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