Materials Literature
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We report the synthesis, film formation, protein resistance, and specific antigen binding capability of a carboxy-functionalized poly(ethylene glycol) alkanethiol [HOOC−CH 2 −(OCH 2 −CH 2 ) n −O−(CH 2 ) 11 −SH, n = 22−45]. Despite its polymeric character, the molecule is found to form a densely packed self-assembled m…
The spectroscopic properties and thermal stability of Er2O3 doped Bi2O3–B2O3–Na2O glasses are investigated experimentally. A close correlation is observed between the B2O3 content and the spectroscopic properties such as Judd–Ofelt intensity parameters Ωt (t=2,4,6), emission spectra, and lifetime of I13/24 level of Er…
This letter describes the electrical control of structure and lasing in the photonic bandgaps of cholesteric liquid crystals (CLCs). Photoexcitation of dye-doped CLC cells with a linearly polarized laser gives rise to laser emission at the edge(s) of the chiral photonic band gap. Applying voltages to the optically pum…
Tunable electronic lenses using gradient polymer network liquid crystal (PNLC) cells were demonstrated. By changing the photomask pattern, both positive and negative lenses were fabricated. The advantages of such a PNLC lens are low operation voltage, large aperture size, and simple electrode design. To overcome the p…
An electroactive pentathiophene surfactant containing a phosphonic acid head group was designed and shown to provide strong binding to the surface of a CdSe nanocrystal and facilitate charge transfer between the nanocrystal and an organic semiconducting matrix (see Figure). Incorporation into organic–inorganic heteroj…
The objective of the present investigation was to fabricate composite colloidal particles consisting of a sacrificial, decomposable template of biodegradable nature covered with biocompatible polyelectrolyte multilayers using the layer-by-layer sequential adsorption technique. Poly-dl-lactic acid and poly(dl-lactic-co…
A new set of wheels: Substituting a chromium ion in [Cr8F8(O2CCMe3)16] with one of a number of alternative transition metals has yielded an unprecedented family of heterometallic wheel complexes (see picture), supported at their centers by secondary ammonium ions. Both 3d (Mn, Fe, Co, Ni) and 4d (Cd) metals have been…
Co‐assembly of binary dispersions of monodisperse microspheres with large size ratios has been used to produce well‐ordered hexagonally close‐packed monolayers of large spheres with a superimposed pattern of small spheres (see Figure). The architectures obtained are determined by the size and concentration ratios of t…
A semicontinuum model is presented for nanostructured materials that possess a platelike geometry, such as ultra-thin films. In contrast to the classical continuum theory, the current model accounts for the discrete nature in the thickness direction. In-plane Young’s modulus, and in-plane and out-plane Poisson’s ratio…
Ultraviolet photoemission spectroscopy is used to determine the energy level alignment at interfaces between three electroactive conjugated organic molecular materials, i.e., N,N′-bis-(1-naphthyl)-N,N′-diphenyl1-1,1-biphenyl1-4,4′-diamine; para-sexiphenyl; pentacene, and two high work function electrode materials, i.e…
Rapid progress in the synthesis and processing of materials with structure on nanometer length scales has created a demand for greater scientific understanding of thermal transport in nanoscale devices, individual nanostructures, and nanostructured materials. This review emphasizes developments in experiment, theory,…
Worldwide experience with polymer concrete high-voltage insulators is surveyed. Particular attention is given to the Brazilian experience, the UK initiative, and the introduction of such insulation in India.>
In the classical partial discharge (PD) measuring circuit the current represents the signal that allows the detection of PDs in the tested sample. This current is converted into a voltage by the measuring impedance, amplified, and filtered. The integration process is essential. A standard calibrator for testing integr…
Fast dynamics and accurate control around zero speed are normally required from process technologies. It is from this perspective that the Ward Leonard field control system is described. Several industrial plants utilizing the Ward Leonard control scheme are in use in South Africa. Multiprocessor digital control syste…
An attempt is made to elucidate the mechanisms causing charge accumulation on and inside insulating spacers. The experiments were conducted inside a glass cruciform vessel which could be evacuated to 10/sup -2/ torr and had a maximum SF/sub 6/ working pressure of 2 bar. Cylindrical spacers of polytetrafluorethylene an…
HPAM (partially hydrolyzed polyacrylamide)/chromium acetate and HPAM/phenolic aldehyde colloidal dispersion gels (CDGs) were investigated microscopically using atomic force microscope. The results show that the colloidal dispersion gels eventually form self‐assembly branch‐like fractal structures over a scanning range…
The authors present results of experiments in which LDPE (low-density polyethylene) and/or XLPE (cross-linked polyethylene) specimens were subjected to mechanical vibrations in water or to mechanical vibrations and electric stress combined. Water tree growth experiments in stretched films of XLPE cable insulation are…
The effect of air density on the flashover voltage of polluted high-voltage insulators has been analyzed for AC, DC, and lightning-wave energizations. The findings, based on the physics of the flashover process and test data from representative models and actual insulators, are presented as an altitude scaling factor.…
An online partial discharge test for large steam turbine generators has been developed whereby partial discharges and noise are distinguished on the basis of pulse width. The pulse signals are detected by stator slot couplers (SSCs) which are permanently installed within the generator. Experiments have shown that part…
A series of experiments was conducted on polymeric insulators to examine the role of molecular bond motion in the recovery of hydrophobicity. The samples were also analyzed with characterization techniques which provided important information concerning surface topography, surface hydrophobicity level, and surface che…