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991.
The non-linear current-voltage characteristic of thermally enhanced field emission is proposed to explain the operation of a metal-metal point contact diode used for laser harmonic frequency generation and frequency mixing in the infrared region. This mechanism can explain several experimental observations which appear inconsistent with the previous analysis based on a planar metal-oxide-metal tunneling geometry. 相似文献
992.
W. F. Lucas 《Probability Theory and Related Fields》1966,6(4):287-292
A symmetric solution is presented for any von Neumann-Morgenstern n-person game when the only coalitions that are not completely defeated contain n– 1 or n players.Portions of this research were supported by a National Science Foundation grant at the University of Michigan and by a Fulbright grant at the Middle East Technical University, Ankara.Mathematics Research Center, The University of Wisconsin, Madison. 相似文献
993.
Angela Pezic Anne‐Louise Ponsonby Fergus J Cameron Christine Rodda Justine A Ellis Jane Halliday William Siero Robyn M Lucas Terence Dwyer 《Photochemistry and photobiology》2013,89(3):714-723
Our aim was to examine the association between ethnicity, phenotype, sun behavior and other characteristics, and constitutive and relative facultative skin pigmentation. A total of 191 participants were recruited, with a mean age of 7.6 years (SD 3.4), during 2009–2011 from Maternal and Child Health Centres (MCHC) and schools in Melbourne, Australia. Parental questionnaire data were obtained on sun behavior and examination consisted of noting the child's natural skin, hair and eye color, ethnicity, nevi count and spectrophotometric melanin density (MD). Constitutive skin pigmentation was estimated from buttock MD. Relative facultative skin pigmentation was estimated by hand compared with buttock absorption. Ethnicity, hair color and skin color were associated with constitutive and facultative skin pigmentation on univariate analysis. Higher ambient ultraviolet radiation (UVR) in the past month, greater freckling, greater nevi and increased sun exposure over the past year were related to darker facultative skin pigmentation. Sun exposure over the life course was not. The two skin charts accounted for 39.7% and 21.4% of buttock MD, respectively. Relative facultative skin pigmentation is associated with recent UVR levels, not life‐course sun exposure. Relative facultative skin pigmentation may not be a useful measure of sun exposure over the early life course. Skin color charts can be used to assess constitutive skin pigmentation if spectrophotometry is not available. 相似文献
994.
Lucas Montero de Espinosa Michael A.R. Meier Author vitae 《European Polymer Journal》2011,(5):837-852
Already for a long time, plant oils and their derivatives have been used by polymer chemists due to their renewable nature, world wide availability, relatively low price, and their rich application possibilities. Although many different synthetic approaches have been used, more recent examples are pointing in the direction of catalytic transformations and other efficient reactions to achieve a more sustainable production of polymers from these renewable resources. In this context, olefin metathesis, thiol–ene additions, and other processes can contribute not only to a more efficient synthesis of plant oil based polymers, but also to broaden the application possibilities of plant oils. This feature article provides an overview of the present situation with special attention to the use of olefin metathesis and thiol–ene chemistry as synthetic methods and as polymerization techniques. 相似文献
995.
Lucas Montero de Espinosa Juan C. Ronda Marina Galià Virginia Cádiz 《Journal of polymer science. Part A, Polymer chemistry》2010,48(4):869-878
The crosslinking reaction of a triglyceride derivative containing α,β‐unsaturated ketones with diaminodiphenylmethane via aza‐Michael addition has been extensively studied. First, a model study with monofunctional compounds showed that the conjugated addition product undergoes a series of transformations leading to formation of a substituted quinoline. The proposed reaction pathway is presented as a variation of the Skraup‐Doebner‐Von Miller quinoline synthesis. The presence of quinolines as crosslinking points in the cured materials has been proved by means of different characterization techniques, and the properties derived from this aromatization process have been described. This new crosslinking approach has been successfully applied to an aldehyde‐containing triglyceride to obtain quinoline‐containing thermosets. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 869–878, 2010 相似文献
996.
997.
ABSTRACT : Aluminium films 2000 Å thick have been bombarded with various flu-ences of 5 keV He+ ions and the resulting bubble distribution observed by Transmission Electron Microscopy. Scanning Electron Microscopy of the films indicates an areal increase in the unsupported regions of the films, which, if it results from three dimensional swelling of the films, is two orders of magnitude larger than would be calculated from the total bubble volume as observed by T. E. M. In addition features closely resembling blisters observed in bulk materials, form on the supported regions of the film. These blisters like features are thought to result from lateral stresses in the films. 相似文献
998.
Ryan M. Bouldin Lucas Kyriazidis Allison Fidler Sethumadhavan Ravichandran Jayant Kumar Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):976-982
A one-pot, environmentally friendly enzymatic method is described for the synthesis a polypyrrole derivative, poly(3-methylpyrrole) (poly(3-MP)) in an aqueous solvent system. The enzyme, soybean peroxidase (SBP), was shown to successfully polymerize the beta functionalized pyrrole monomer. The resulting polymer was semiconducting, thermally stable, and exhibited bipolaron absorptions when synthesized in the presence of poly(sodium 4-styrenesulfonate) (PSS). Polymers synthesized in the presence of 10-camphor sulfonic acid (CSA) were found to exhibit slightly higher conductivity values, but were less thermally stable compared to poly(3-MP) polymerized in the presence of PSS. This work should stimulate further interest in expanding the use of enzymes as catalysts for the polymerization of other pyrrole derivatives, as well as other classes of conjugated polymers. 相似文献
999.
M. R. Ehrhardt T. O. Monz T. W. Root R. K. Connelly C. T. Scott D. J. Klingenberg 《Applied biochemistry and biotechnology》2010,160(4):1102-1115
The rheological properties of acid hydrolyzed corn stover at high solids concentration (20–35 wt.%) were investigated using
torque rheometry. These materials are yield stress fluids whose rheological properties can be well represented by the Bingham
model. Yield stresses increase with increasing solids concentration and decrease with increasing hydrolysis reaction temperature,
acid concentration, and rheometer temperature. Plastic viscosities increase with increasing solids concentration and tend
to decrease with increasing reaction temperature and acid concentration. The solids concentration dependence of the yield
stress is consistent with that reported for other fibrous systems. The changes in yield stress with reaction conditions are
consistent with observed changes in particle size. This study illustrates that torque rheometry can be used effectively to
measure rheological properties of concentrated biomass. 相似文献
1000.
Luciana S. Spinelli Genecy R. Neto Layla F.A. Freire Vitor Monteiro Rosana Lomba Ricardo Michel Elizabete Lucas 《Colloids and surfaces. A, Physicochemical and engineering aspects》2010,353(1):57-63
Aphrons fluids, because of their “noninvasive” characteristic, are indicated for drilling zones that have multiple intercalations of depleted formations adjacent to formations that require high-density fluids. Aphrons are colloidal dispersions containing microbubbles, with cores of gas, liquid or emulsion ranging from 10 to 100 μm in diameter, that are highly stable due to their high interfacial area and multiple surrounding surfactant layers. This paper presents results of physical–chemical properties, bubble size distribution and filtration of systems containing microbubbles. The aphrons were generated by applying a pressure differential under a high-pressure high-temperature (HPHT) filtration cell. Tests were also run with different types of surfactants, specific for generation of bubbles in an organic medium (ester). The surfactants were analyzed for their surface tension and the dispersions produced were photographed under an optical microscope at 60× magnification. The images obtained were digitized to enable determination of the bubble size distribution using an ImageJ program. The filtrate reduction performance of these fluids was determined by static filtration in synthetic porous media. There was a correlation between the filtration characteristics of the fluids, the bubble size distribution and number of bubbles produced in each base and for each surfactant tested. The results obtained served as a reference to formulate a light, non-water-based drilling fluid containing microbubbles with “noninvasive” characteristics. 相似文献