RF microelectronics for W-CDMA mobile communication systems

Third generation (3G) mobile communication systems are now just starting to be introduced. With a maximum data rate of 2 Mbit/s they will make wireless access to broadband data services like the Internet or video applications feasible. Most of the different physical layer technologies summarised under the acronym 3G are based on wideband-CDMA (W-CDMA), in contrast to existing second generation systems, which mostly use TDMA and FDMA. This has severe consequences for the design of the transceiver front-ends. During standardisation these were assumed to have an adequate RF performance yet they still present a performance bottleneck for the system. Starting with a short introduction to UMTS (Universal Mobile Telecommunications System)-the 3G standard to be deployed in Europe and already operating in Japan-this paper describes by way of example some of the test cases specified for UMTS and their impact on the analogue front-end. It is shown that accurate simulation of all the analogue and digital signal processing is necessary in order to predict the RF performance needed of today's commercial RFICs. The paper then presents and reviews some actual design examples. Finally, possible technologies and techniques for application in future mobile terminals are discussed     

Action of chelators on solid iron in phosphate-containing aqueous solutions

To study the effect of strong iron-ligands on steel corrosion, mild steel electrodes were immersed in solutions containing 20 mM phosphate buffer (pH=7.2) and between 0.01 mM and 1 M of either the iron(II)-chelators 2,2^′-bipyridine or FerroZine, or the iron(III)-chelators citrate or acetylacetonate. Resulting surface reactions were investigated by quantifying the electrochemical potential (E), the electrochemical polarization resistance (R_p), the corrosion current (I_corr) and the release of iron into solution. The surface was further analyzed by scanning electron microscopy (SEM/SEM-EDAX) and atomic force microscopy. Concentrations of 0.1 mM of any of the chelators led to slight, temporary changes in E, I_corr and R_p. Concentrations of 10 mM resulted in characteristic changes of E, which were the same for all chelators and in the precipitation of FePO₄ in the case of citrate and acetylacetonate, or vivianite [Fe₃(PO₄)₂ · 8H₂O] in the case of bipyridine and FerroZine. Concentrations of 1 mM of both iron(III)-chelators led to a temporary drop of E similar to that found with 0.1 mM chelator. With iron(II)-chelators, E dropped to about −500 mV before oscillating for several days. The amplitudes of the oscillations were up to 200 mV with periods of 30 and 20-25 min for bipyridine and FerroZine, respectively.     

Gunn effect in MESFET-like structures

The performance of planar field-effect controlled transferred electron oscillators with different combinations of layer thickness and doping concentration has been investigated. A negative differential resistance has even been obtained with 0.29 mu m thick 1.6*10/sup 17/ cm/sup -3/ n-doped samples. This is the first time a MESFET-like active layer has exhibited the Gunn effect and has successfully been operated as a TEO at 36 GHz.<>     

Microwave and millimeterwave oscillator developments at the Johannes Kepler University

This contribution reviews the research work performed at the Johannes Kepler University of Linz, Austria, on the development of oscillators for the microwave and millimeter wave frequency range. This work, performed by the Microelectronics Institute and the Institute for Communications and Information Engineering, covers the range from low GHz frequencies up to 61 GHz and is devoted to applications like mobile communications and sensing. The active devices are based on gallium arsenide (GaAs), silicon germanium (SiGe), and Silicon (Si) and include Gunn-devices, bipolar transistors, and CMOS-technology.     

Crystal structure of ICAM-2 reveals a distinctive integrin recognition surface

Recognition by integrin proteins on the cell surface regulates the adhesive interactions between cells and their surroundings. The structure of the 'I' domain that is found in some but not all integrins, has been determined. However, the only integrin ligands for which structures are known, namely fibronectin and VCAM-1, are recognized by integrins that lack I domains. The intercellular adhesion molecules ICAM-1, 2 and 3 are, like VCAM-1, members of the immunoglobulin superfamily (IgSF), but they are recognized by an I domain-containing integrin, lymphocyte-function-associated antigen 1 (LFA-1, or CD11a/CD18). Here we present the crystal structure of the extracellular region of ICAM-2. The glutamic acid residue at position 37 is critical for LFA-1 binding and is proposed to coordinate the Mg2+ ion in the I domain; this Glu 37 is surrounded by a relatively flat recognition surface and lies in a beta-strand, whereas the critical aspartic acid residue in VCAM-1 and fibronectin lie in protruding loops. This finding suggests that there are differences in the architecture of recognition sites between integrins that contain or lack I domains. A bend between domains 1 and 2 of ICAM-2 and a tripod-like arrangement of N-linked glycans in the membrane-proximal region of domain 2 may be important for presenting the recognition surface to LFA-1. A model of ICAM-1 based on the ICAM-2 structure provides a framework for understanding its recognition by pathogens.     

Pharmacies during the transformation of health care. IV. Sociologic study of pharmacy service

In Slovakia, similarly as in the Czech Republic, marked changes in the pharmaceutical services have gradually been taking place since 1990. Principal legal and organizational changes have been connected also with the extent and standard of provided pharmaceutical services. The present paper reports the results of a questionnaire research regarding the evaluation of the standard of pharmaceutical services in the year 1995 where there existed both state-owned and private public pharmacies. The questionnaire research was carried out in 20 pharmacies of the Region of West Slovakia, 407 questionnaires were evaluated. The questionnaires were evaluated from the viewpoint of sociological classification of respondents (economically active persons, old-age pensioners) as well as the sex of pharmacy customers. The results confirmed relatively little significant differences between the satisfaction with pharmaceutical services either according to the sex or the social position of the respondents. A relatively significant proportion of the respondents have expressed critical views about the participation of the patient in covering the costs of drugs and slow execution of order of drugs.     

Two-laboratory collaborative study on identification of mycobacteria: molecular versus phenotypic methods

Previous studies have indicated that the conventional tests used for the identification of mycobacteria may (i) frequently result in erroneous identification and (ii) underestimate the diversity within the genus Mycobacterium. To address this issue in a more systematic fashion, a study comparing phenotypic and molecular methods for the identification of mycobacteria was initiated. Focus was given to isolates which were difficult to identify to species level and which yielded inconclusive results by conventional tests performed under day-to-day routine laboratory conditions. Traditional methods included growth rate, colonial morphology, pigmentation, biochemical profiles, and gas-liquid chromatography of short-chain fatty acids. Molecular identification was done by PCR-mediated partial sequence analysis of the gene encoding the 16S rRNA. A total of 34 isolates was included in this study; 13 of the isolates corresponded to established species, and 21 isolates corresponded to previously uncharacterized taxa. For five isolates, phenotypic and molecular analyses gave identical results. For five isolates, minor discrepancies were present; four isolates remained unidentified after biochemical testing. For 20 isolates, major discrepancies between traditional and molecular typing methods were observed. Retrospective analysis of the data revealed that the discrepant results were without exception due to erroneous biochemical test results or interpretations. In particular, phenotypic identification schemes were compromised with regard to the recognition of previously undescribed taxa. We conclude that molecular typing by 16S rRNA sequence determination is not only more rapid (12 to 36 h versus 4 to 8 weeks) but also more accurate than traditional typing.     

The mechanical properties of laminated microscale composites of Al/Al2O3

The tensile properties, at both room and elevated temperatures, of laminated thin films containing alternate layers of aluminium and aluminium oxide were investigated. At room temperature the strength of the films followed a Hall-Petch type relationship dependent on the interlamellar spacing, and the strength could be extrapolated from data for conventional grain size aluminium. At the finest interlayer spacing of 50 nm, the strength was equivalent to/70, where is the shear strength of aluminium and the samples exhibited very extensive ductility. At elevated temperatures, cavitation became an important deformation mechanism but it occurred preferentially at Al/Al rather than Al/Al₂O₃ boundaries. The microstructure of the films was probed using transmission electron microscopy and fractography was used to investigate deformation and fracture mechanisms.