PCM-FDM System for Existing Microwave Radio Baseband

Digital transmission over the empty lower baseband of an existing microwave radio system has the advantages of economical and easy construction. A 1.544 Mbit/s PCM-FDM converter (PF-B1) has been developed. Field test results show that the error-rate per bit is less than 10^-8over 840 km with 3 basebands.     

Quantitative Estimate Index for Early-Stage Screening of Compounds Targeting Protein-Protein Interactions

Drug-likeness quantification is useful for screening drug candidates. Quantitative estimates of drug-likeness (QED) are commonly used to assess quantitative drug efficacy but are not suitable for screening compounds targeting protein-protein interactions (PPIs), which have recently gained attention. Therefore, we developed a quantitative estimate index for compounds targeting PPIs (QEPPI), specifically for early-stage screening of PPI-targeting compounds. QEPPI is an extension of the QED method for PPI-targeting drugs that models physicochemical properties based on the information available for drugs/compounds, specifically those reported to act on PPIs. FDA-approved drugs and compounds in iPPI-DB, which comprise PPI inhibitors and stabilizers, were evaluated using QEPPI. The results showed that QEPPI is more suitable than QED for early screening of PPI-targeting compounds. QEPPI was also considered an extended concept of the “Rule-of-Four” (RO4), a PPI inhibitor index. We evaluated the discriminatory performance of QEPPI and RO4 for datasets of PPI-target compounds and FDA-approved drugs using F-score and other indices. The F-scores of RO4 and QEPPI were 0.451 and 0.501, respectively. QEPPI showed better performance and enabled quantification of drug-likeness for early-stage PPI drug discovery. Hence, it can be used as an initial filter to efficiently screen PPI-targeting compounds.     

Millimeter-Wave over Fiber Systems Using Hybrid OCDM/WDM Transmission

In this paper, we propose and simulate 2 OCDM × 4 WDM transmission system for a millimeter-wave (60 GHz) over fiber system to be used in broadband wireless access networks (BWANs). The general system setup is devised and the necessary building blocks identified. Results gathered (for a 155 Mbit/s per user system) under worst case parameter specifications and settings suggest indicate that system performance is severely limited by optical multiuser interference (OMUI) penalties. Several methods to reduce the OMUI limitations are described. These methods should ensure that this transmission scheme possible wavelength-reuse option for future MMW BWANs.     

Hygroscopic Growth of an (NH 4 ) 2 SO 4 Aqueous Solution Droplet Measured Using an Environmental Scanning Electron Microscope (ESEM)

The contact angle, θ, and volume equivalent diameter of an (NH₄)₂SO₄ aqueous droplet was measured using an environmental scanning electric microscope (ESEM), showing the hygroscopic growth of the solution droplet as the relative humidity (RH) increased from 80% to 98%. (NH₄)₂SO₄ particles with diameters in the range 1–2 μ m were produced by an atomization technique, and collected onto a copper substrate that had been treated with polytetrafluoroethylene. To observe the hygroscope growth, the sample chamber of the ESEM was filled with water vapor at a pressure of 600 Pa, and the sample temperature was adjusted using a cooling stage to control the relative humidity inside the chamber. Before the observation of the hygroscopic growth, we determined the value of θ from overhead views of droplets on the stage at a tilted angle of 45°. The average value of θ was 96 ± 10°, and this value was used to estimate the droplet diameter. We measured the diameter of the (NH₄)₂SO₄ droplets at different RH, and observed that the growth factor, G, increased with increasing RH. The experimental value of G was consistent with the theoretically estimated value. This shows that our method for determining the value of θ was valid, and that the ESEM technique can be used to measure the diameters of droplets of aqueous solutions.     

Preparation of endohedral metallofullerene nanowhiskers and nanosheets

Endohedral metallofullerene nanowhiskers and nanosheets were prepared using pristine Sc₃N@C₈₀ by liquid-liquid interfacial precipitation. This means that it is possible to prepare endohedral metallofullerene structures without using chemical derivatization techniques. They were characterized using scanning and transmission electron microscopy and atomic force microscopy. The morphology of the prepared Sc₃N@C₈₀ structures could be tailored by merely changing the solvent used for the interfacial precipitation.     

Micro-raman characterization of molecular-beam epitaxial ge heterolayers on Si substrates

Molecular-beam epitaxial germanium heterolayers on silicon are characterized by micro-Raman spectroscopy. The samples are angle-lapped to probe the near-interface region. A small positive shift in the germanium phonon frequency is observed near the interface compared with the surface of the 1 μm thick layer. This indicates that the misfit stress is not relaxed completely in the as-grown layers. The samples are annealed at 700°C, a temperature higher than the growth temperature, and then the germanium peak shifts toward lower frequency near the interface. This would be due to both thermal stress and formation of an interfacial alloy layer by the interdiffusion. After annealing at 850°C, the germanium peak shifts downward further because of the interdiffusion, and the peak due to the Si−Ge vibration is clearly observed near the interface.     

Escort: an environment for specifying communication requirements

A prototype specification support system, Escort, is described that incorporates novel validation, verification, and simplification methods for telecommunications software specifications. Unix was adapted as the operating system for Escort, and many of Escort's tools were designed and implemented by making full use of the Unix facilities. Escort identifies three kinds of specification errors: errors in the grammar of the specification language, called syntax errors; those that degrade consistency and completeness, called logical errors; and those that degrade correctness, called semantic errors. It detects these errors using syntax analysis, validation, and verification, respectively     

Spectroscopic study on the centrifugal fractionation of soluble single-walled carbon nanotubes

Optical absorption and resonant Raman spectra are proven to be convenient and effective to monitor the centrifugal fractionation and to evaluate the quality of soluble single-walled carbon nanotubes (SWNTs) achieved by inorganic oxidation and organic functionalization. Through a systemic study of a series of centrifuged solutions, we confirmed that heavily functionalized amorphous carbon was fractionated into the early centrifuged solutions, whereas lightly functionalized graphite fragments as well as polyhedral carbon and metal catalysts particles were fractionated into the late centrifuged solutions and centrifuged residue, and then highly pure and well dispersed SWNTs were collected from the middle centrifuged solutions. It is proposed that the purity, dispersibility, and aggregation state of SWNTs can be qualitatively estimated by the relative intensity of their absorption features, the fine structure and slope of their absorption curves. The Raman features of centrifuged SWNTs are found systematically up-shifted except the disorder-induced D band in comparison with those of as-prepared material, indicating that the SWNTs in centrifuged solutions are individual or in thin bundles. Two new features were identified at 1428 and 941 cm⁻¹ in the Raman spectrum of thermally annealed centrifuged SWNTs, which were assigned to achiral nanotubes and combined mode, respectively.