83,907 research outputs found
Aluminum ion-containing polyimide adhesives
A meta-oriented aromatic diamine is reacted with an aromatic dianhydride and an aluminum compound in the presence of a water or lower alkanol miscible ether solvent to produce an intermediate polyamic acid. The polyamic acid is then converted to the thermally stable, metal ion-filled polyimide by heating in the temperature range of 300 C to produce a flexible, high temperature adhesive
The employment effect in retail trade of California's 1988 minimum wage increase
In this paper, the authors study the outcome of an unusually clean natural experiment--California's large minimum wage increase of 1988. Two different approaches to evaluating the experiment result in the same conclusion: the textbook analysis of minimum wages holds true. In particular, the authors find that employment growth in California's low-wage retail trade industry was slowed by the minimum wage increase.
Mechanical and spectroscopic properties of metal-containing polyimides
The incorporation of specific metal ions into polyimides is described. Detailed studies have included various compounds of copper, lithium, and palladium as dopants. Addition of the metal during polymerization or after formation of the polyamic acid precedes the thermal imidization step. With many dianhydride-diamine-dopant combinations high quality variously colored films are produced. Many metal doped films exhibit (1) improved high temperature adhesive properties, (2) increased electrical conductivity, (3) excellent thermal stability, (4) improved acid/base resistance, (5) increased modulus in flexible films and (6) excellent high temperature tensile strength. X-ray photo-electron spectroscopic study of these films suggests that many of the additives undergo chemical modification during thermal imidization. Palladium dopants appear to be partially reduced to the metallic state, while lithium and copper dopants are probably converted to their oxides. Ion etching experiments with Auger electron spectroscopy monitoring are discussed
Some transition metal complexes of 8-amino- quinoline
Transition metal complexes of 8-aminoquinolin
Time Variable Faraday Rotation Measures of 3C-273 and 3C-279
Multifrequency polarimetry with the VLBA confirms the previously reported
time-varying Faraday rotation measure (RM) in the quasar 3C-279. Variability in
the RM and electric vector position angle (EVPA) of the jet component (C4) is
seen making it an unreliable absolute EVPA calibrator. 3C-273 is also shown to
vary its RM structure on 1.5 year time-scales. Variation in the RM properties
of quasars may result from a Faraday screen which changes on time-scales of a
few years, or from the motion of jet components which sample spatial variations
in the screen. A new component emerging from the core of 3C-279 appears to be
starting to sample such a spatial variation. Future monitoring of this
component and its RM properties is suggested as a diagnostic of the narrow line
region in 3C-279. We also present a new method of EVPA calibration using the
VLA Monitoring Program.Comment: Accepted to ApJ Letters. 12 pages, 5 figure
Topological Insulator Magnetic Tunnel Junctions: Quantum Hall Effect and Fractional Charge via Folding
We provide a characterization of tunneling between coupled topological
insulators in 2D and 3D under the influence of a ferromagnetic layer. We
explore conditions for such systems to exhibit integer quantum Hall physics and
localized fractional charge, also taking into account interaction effects for
the 2D case. We show that the effects of tunneling are topologically equivalent
to a certain deformation or folding of the sample geometry. Our key advance is
the realization that the quantum Hall or fractional charge physics can appear
in the presence of only a \emph{single} magnet unlike previous proposals which
involve magnetic domain walls on the surface or edges of topological insulators
respectively. We give illustrative topological folding arguments to prove our
results and show that for the 2D case our results are robust even in the
presence of interactions.Comment: 5 pages, 2 figure
Mesomorphic properties of alkoxybenzylidene- aminoacetophenones
Liquid crystal phase transitions in compounds of alkoxybenzylidene-aminoacetophene serie
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