Porphyrins with metal, metalloid or phosphorus atoms directly bonded to the carbon periphery

Organometallic porphyrins with a metal, metalloid or phosphorus fragment directly attached to their carbon framework emerged for the first time in 1976, and these macrocycles have been intensively investigated in the past decade. The present review summarises for the first time all reported examples as well as applications of these systems.

Elite Bargaining and the Evolution of Centre-Periphery Relations in Post-Soviet Russia : A Comparative Analysis

This work is concerned with presenting a modified theoretical approach to the study of centre-periphery relations in the Russian Federation. In the widely accepted scientific discourse, the Russian federal system under the Yeltsin Administration (1991-2000) was asymmetrical; largely owing to the varying amount of structural autonomy distributed among the federation s 89 constituent units. While providing an improved understanding as to which political and socio-economic structures contributed to federal asymmetry, it is felt that associated large N-studies have underemphasised the role played by actor agency in re-shaping Russian federal institutions. It is the main task of this thesis to reintroduce /re-emphasise the importance of actor agency as a major contributing element of institutional change in the Russian federal system. By focusing on the strategic agency of regional elites simultaneously within regional and federal contexts, the thesis adopts the position that political, ethnic and socio-economic structural factors alone cannot fully determine the extent to which regional leaders were successful in their pursuit of economic and political pay-offs from the institutionally weakened federal centre. Furthermore, this work hypothesises that under conditions of federal institutional uncertainty, it is the ability of regional leaders to simultaneously interpret various mutable structural conditions then translate them into plausible strategies which accounts for the regions ability to extract variable amounts of economic and political pay-offs from the Russian federal system. The thesis finds that while the hypothesis is accurate in its theoretical assumptions, several key conclusions provide paths for further inquiry posed by the initial research question. First, without reliable information or stable institutions to guide their actions, both regional and federal elites were forced into ad-hoc decision-making in order to maintain their core strategic focus: political survival. Second, instead of attributing asymmetry to either actor agency or structural factors exclusively, the empirical data shows that both agency and structures interact symbiotically in the strategic formulation process, thus accounting for the sub-optimal nature of several of the actions taken in the adopted cases. Third, as actor agency and structural factors mutate over time, so, too do the perceived payoffs from elite competition. In the case of the Russian federal system, the stronger the federal centre became, the less likely it was that regional leaders could extract the high degree of economic and political pay-offs that they clamoured for earlier in the Yeltsin period. Finally, traditional approaches to the study of federal systems which focus on institutions as measures of federalism are not fully applicable in the Russian case precisely because the institutions themselves were a secondary point of contention between competing elites. Institutional equilibriums between the regions and Moscow were struck only when highly personalised elite preferences were satisfied. Therefore the Russian federal system is the product of short-term, institutional solutions suited to elite survival strategies developed under conditions of economic, political and social uncertainty.

Wave digital filter model of the entire auditory periphery

A model of the auditory periphery assembled from analog network submodels of all the relevant anatomical structures is described. There is bidirectional coupling between networks representing the outer ear, middle ear and cochlea. A simple voltage source representation of the outer hair cells provides level-dependent basilar membrane curves. The networks are translated into efficient computational modules by means of wave digital filtering. A feedback unit regulates the average firing rate at the output of an inner hair cell module via a simplified modelling of the dynamics of the descending paths to the peripheral ear. This leads to a digital model of the entire auditory periphery with applications to both speech and hearing research.

1-mm gate periphery AlGaN/AIN/GaN HEMTs on SiC with output power of 9.39 W at 8 GHz

AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with high mobility GaN channel layer were grown on 50 min diameter semi-insulating (SI) 6H-SiC substrates by metalorganic chemical vapor deposition and large periphery HEMT devices were fabricated and characterized. High two-dimensional electron gas mobility of 2215 cm(2)/V s at room temperature with sheet electron concentration of 1.044 x 10(13)/cm(2) was achieved. The 50 mm diameter HEMT wafer exhibited a low average sheet resistance of 251.0 Omega/square, with the resistance uniformity of 2.02%. Atomic force microscopy measurements revealed a smooth AlGaN surface with a root-mean-square roughness of 0.27 nm for a scan area of 5 mu mi x 5 pm. The 1-mm gate width devices fabricated using the materials demonstrated a very high continuous wave output power of 9.39 W at 8 GHz, with a power added efficiency of 46.2% and power gain of 7.54 dB. A maximum drain current density of 1300 mA/mm, an extrinsic transconductance of 382 mS/mm, a current gain cutoff frequency of 31 GHz and a maximum frequency of oscillation 60 GHz were also achieved in the same devices. (C) 2007 Elsevier Ltd. All rights reserved.

Study on a carbosilane liquid crystalline (LC) dendrimer of the first generation - Containing twelve 4-butoxyazobenzene mesogenic groups in periphery

The divergent synthesis of a new carbosilane liquid-crystalline (LC) dendrimer of the first generation (D1) is described. Twelve 4-butoxyazobenzene groups are used as mesogenic fragments and attached in the periphery of the molecule. Structure and properties of D1 were characterized by element analysis, H-1 NMR, MALDI-TOF-MS, IR, UV-Vis, polarizing optical micrograph, DSC and WAXD. It is argued that mesophase of nematic type is realized. It is shown that the mesophase type of the dendrimer essentially depends on the chemical nature of the mesogenic groups. Phase behavior of D1 is K82N1331132N67K. The melting point of D1 is 30similar to43 degreesC lower than that of M5, its clearing temperature is 9 similar to 11 degreesC higher than that of M5 and its mesophase region is enlarged by 39 similar to 54 degreesC compared to that of M5. Eight extinguished brushes emanating from a stationary point are observed, corresponding to the high-strength disclination of S = + 2 of dendrimer. The clearing enthalpy of D1 is smaller than the value that is commonly found for phase transition n-i in LC and LC polymers. This may be due to the presence of branched dendrimer cores which cannot be easily deformed to fit into the anisotropic LC phase structure.

Models of core/periphery structures

A common but informal notion in social network analysis and other fields is the concept of a core/periphery structure. The intuitive conception entails a dense, cohesive core and a sparse, unconnected periphery. This paper seeks to formalize the intuitive notion of a core/periphery structure and suggests algorithms for detecting this structure, along with statistical tests for testing a priori hypotheses. Different models are presented for different kinds of graphs (directed and undirected, valued and nonvalued). In addition, the close relation of the continuous models developed to certain centrality measures is discussed.