A region-specific microdissection library for human chromosome 2p23-->p21 and the analysis of an interstitial deletion of 2p21

A region-specific library of human chromosome 2p23-->p21 was constructed using microdissection and microcloning techniques. Analysis of 94 single-copy microclones from the library showed that 64% were derived from the dissected region. Ten microclones were further mapped to the 2p21 region using a patient with an interstitial deletion of 2p21 and displaying holoprosencephaly, an abnormal embryonic development in midbrain and midface.     

Phase dynamics and radiated power of dc SQUIDS

The time variation of the quantum phase difference and the radiated power of two resistively shunted junctions in a superconducting loop are analyzed using a first harmonic approximation method. It is shown explicitly that an output coupling impedance connected across the junctions plays an important role in determining the output power as well as the cutoff frequency in the radiation spectrum. The radiated power of an array of dc SQUIDs is compared with the power output of a synchronized series array in a resonant cavity. WithN superconducting weak links coupled to a fixed load, the SQUID array suffers an output power saturation for largeN; our analysis shows that it is very difficult to obtain radiated power higher than a few microwatts. On the other hand, a cavity-coupled large array gives an output power proportional toN with a narrow linewidth, suggesting that it could be very useful in practice.     

Signal light amplification by stimulated Raman scattering in anN-channel WDM optical fiber communication system

The use of forward and backward Raman amplification in an N -channel wavelength-division-multiplexing (WDM) optical-fiber communication system is analyzed. Analytical expressions for the signals, the pumps, and the amplified spontaneous scattered power (ASSP) are presented. The crosstalk among the signal channels is analyzed in terms of system parameters. It is found that the crosstalk is negligible while low pump power is used and becomes significant if high pump power is used. The signal-to-ASSP ratio can be improved by increasing pump power; however, the improvement is small when pump power is already high. A 300-km repeater spacing with more than 20-dB signal-to-ASSP ratio is calculated     

Positron trapping at phase interfaces and dislocations in pearlitic eutectoid steel

Positron annihilation studies of isothermally annealed eutectoid steel revealed that positrons prefer to trap and annihilate at discrete dislocations rather than phase interfaces. PO-WE KAO, formerly with the Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT.     

Fabrication and percolation behaviour of novel porous conductive polyblends of polyaniline and poly(methyl methacrylate)

The conductive polymer polyaniline is blended with conventional industrial thermoplastics in order to obtain an electrically conductive polymer blend with adequate mechanical properties. Processing these polyblends into foams yields a porous conductive material that exhibits immense application potential such as dynamic separation media and low-density electrostatic discharge protection. In the current study, the morphology of a thermally processable blend consisting of an electrically conductive polyaniline-dodecylbenzene sulfonic acid complex and poly(methyl methacrylate) is explored using a two-phase batch foaming setup. The effect of blend composition and processing parameters on the resulting porous morphology is investigated. The impact of the underlying microstructure and blend composition on the frequency dependent electrical conductivity is elucidated using multiple linear regression and a model is proposed. Finally, dielectric analysis is utilized to experimentally identify the critical dispersion frequency of an unfoamed blend composition near the percolation threshold.     

Improved electron injection into Alq3 based OLEDs using a thin lithium carbonate buffer layer

A cathode buffer layer of lithium carbonate (Li₂CO₃) we used to improve the electro-optical properties of organic light-emitting diodes (OLEDs). Li₂CO₃ layers with various thicknesses were prepared by thermally evaporating Li₂CO₃ powders. When a 1-nm-thick Li₂CO₃ layer was inserted between the aluminum (Al) cathodes and tris(8-hydroxyquinolinato)aluminum (Alq₃) electron-transporting layers, device properties such as the turn-on voltage, the maximum luminance, and the device efficiency were improved, becoming better than and comparable to those of devices with LiF and Cs₂CO₃ buffer layers. The surface of the Alq₃ film became smoother after the Li₂CO₃ layer was deposited. The reaction mechanisms between Li₂CO₃ and Alq₃ were also investigated. X-ray and ultraviolet photoelectron spectroscopy results show that some electrons transfer from Li₂CO₃ into Alq₃, which increases the electron concentration in Alq₃ films and moves the Fermi level close to the lowest unoccupied molecular orbital (LUMO) of Alq₃. Thus, the electron injection efficiency was enhanced due to a lower electron injection barrier, which improves the charge carrier balance in OLEDs and leads to better device efficiency.