2-Cyano-2-butylazoformamidoethyl 4-t-butylazo-4-cyanopentanoate synthesis and its behaviour in methyl methacrylate polymerization

Synopsis In the present paper the synthesis of a new bis-azo initiator, 2-cyano-2-butylazo-formamidoethyl 4-t-butylazo-4-cyanopentanoate, is reported. The structures of the intermediates and of the initiator were confirmed by the IR and ¹H-NMR spectral measurements. The polymerization of methyl methacrylate (MMA) in the presence of this initiator was studied and the conversion-time dependence followed with different concentrations of the initiator and of the monomer.     

L'eliminazione delle oscillazioni spurie negli amplificatori e oscillatori a diodo IMPATT (Elimination of the low-frequency spurious oscillations in IMPATT amplifiers and oscillators)

Le oscillazioni spurie in bassa frequenza dei diodi IMPATT possono essere evitate mediante I'impiego di una nuova soluzione. Essa é basata sull'uso di una ferrite a microonde (nonpolarizzata magneticamente) in prossimità del diodo. Essa si comporta come un dielettrico nello spettro delle microonde e come un materiale magnetico ad alte perdite nell'intervallo delle frequenze spurie (basse frequenze). IMPATT-diode low-frequency spurious oscillations can be avoided by using a magnetically unbiased microwave ferrite close to the diode. It behaves as a low-loss dielectric in the microwave spectrum and a high-loss material in the spurious (low-frequency) range.     

A preliminary macroinvertebrate Index of Biotic Integrity for bioassessment of the Kipkaren and Sosiani Rivers,Nzoia River basin,Kenya

Management efforts for the Lake Victoria Basin have been hampered by a lack of clear standards against which to judge the degree of environmental degradation, highlighting the need for a multi‐metric approach for this purpose. Indeed, management priorities for the Lake Victoria catchment must be based on reliable assessments of the biological integrity of the inflowing rivers that can potentially influence the ecological functioning of the lake. Accordingly, macroinvertebrate metrics were evaluated for their responsiveness to human impacts, utilizing Pearson’s correlations with physico‐chemical parameters. The resultant 9 metrics that provided the best discrimination between physico‐chemical samples, using the separation power of Mann–Whitney U and Kolmogorov–Smirnov tests (P < 0.05) from the 21 sampling sites utilized in this study were the: (i) abundances of Ephemeroptera, Plecoptera and Trichoptera; (ii) relative abundances of Diptera; (iii) Ephemeroptera, Plecoptera and Trichoptera:Diptera ratio; (iv) Oligochaeta, Mollusca, Hemiptera, Odonata and the proportions of tolerance taxa; (v) dominant taxa; and (vi) the relative proportions of invertebrates that fall into the gatherer and predator feeding groups, based on the variability they exhibited across the sampling sites. Using the inter‐quartile ranges to establish the scoring criteria, the index was able to delineate impacted from less‐impacted sites along the rivers, providing preliminary evidence of responses to changes in the ecosystem integrity exhibited by resident macroinvertebrate assemblages in both rivers.     

Force-velocity properties and myosin light chain isoform composition of an identified type of skinned fibres from rat skeletal muscle

Force-velocity relations, myosin heavy chain (MHC) and myosin light chain (MLC) isoform composition of single skinned fibres from rat plantaris muscle were determined. In fibres containing the same (2X) isoform of myosin heavy chain, several parameters derived from the force-velocity relation and isometric force (Po) were tested for relation with the fibre content in alkali myosin light chain (MLC) isoforms. Whereas maximum shortening velocity was found to be proportional to the relative content in the 3f isoform of alkali MLC, velocity of shortening at 5% relative load, maximum power output, and Po were not. These results strengthen the idea that, in mammalian skeletal fibres, alkali MLC isoforms modulate shortening velocity at zero load, but suggest that they do not control the contractile behaviour at loads higher than zero.     

QoS Routing for Mesh-Based Wireless LANs

Wireless LANs with their increased data rate become an attractive technology for connecting mobile users to the Internet. Efficient deployment of wireless LANs will require the ability to extend the wireless LANs coverage without the need to deploy a very large number of access points. Mesh-based wireless LANs are an attractive solution to this problem. These networks extend wireless LAN coverage by using each node in the network as a router, resulting in a multihop topology. In this paper we introduce a novel routing algorithm, wireless mesh routing (WMR), that provides quality-of-service (QoS) support and accounts for the characteristics of both infrastructure-based wireless LANs and ad hoc networks. The algorithm is validated using the OPNET modeler. The simulation results show that the mesh network using WMR protocol can provide QoS support and react dynamically to the network status changes with low control overheads. Using the proposed software architecture the proposed routing protocol can be implemented with any MAC protocol, resulting in easy implementation in existing wireless nodes.     

Effects of High-κ (HfO2) Gate Dielectrics in Double-Gate and Cylindrical-Nanowire FETs Scaled to the Ultimate Technology Nodes

In this work we investigate the performance of double-gate and cylindrical nanowire FETs with high-kappa gate dielectrics at their extreme miniaturization limits. The model fully accounts for quantum electrostatics; current transport is simulated by an improved quantum drift-diffusion approach supported by a new thickness-dependent mobility model which nicely fits the available measurements for both SiO₂ and HfO₂ gate dielectrics. The on-current is simulated using both the quantum drift-diffusion model and a full-quantum transport approach based on the quantum transmitting boundary method, which assumes a purely ballistic transport. The performance comparison between SiO₂ and HfO₂ insulated-gate FETs with the same electrical oxide thickness demonstrates that the latter provides a slight degradation of the short-channel effect compared with the former but, at the same time, gives an improved on-current due to lateral capacitive-coupling effects, despite the inherent degradation of the low-field mobility     

Accessibility and Network Structures in the German Commuting

A great deal of attention has recently been paid to the analysis of the structure and evolution of (complex) networks, starting from pioneering contributions in the physical and social sciences—and more recently in the regional and transportation sciences—mainly concerning the relevance of highly connected nodes (hubs). The presence of hubs identifies a network as Scale-Free (SF), because of its intrinsic characteristic of exhibiting power-law distributions in its connectivity structure, and thus highly heterogeneous patterns. The focus of this paper is to explore the homogeneous vs. heterogeneous characteristics of the German commuting network, by focusing on the role of accessibility. The concept of accessibility has a long tradition in the transport economics literature, starting with the fundamental works by Hansen in the 1950’s and later on by Weibull in the 1980’s. These authors defined accessibility as the potential of opportunities for spatial interaction. Accessibility conceived in this manner should also capture spatial structure effects and thus the network configuration properties, such as connectivity. This conventional accessibility function—in the light of the related economic activities—is be used as a suitable instrument to identify the major German hub/attraction nodes. As the functional form in this potential accessibility, the power-decay function will be considered—in addition to the negative exponential function—in order to explore the spatial configuration patterns, i.e. whether people perceive commuting cost in log-like way. The connectivity network analysis will then be developed as a benchmark to testing the results emerging from the spatial-economic analysis. In our application we consider home-to-work commuters travelling between 439 German districts, for the year 2002. The final results seem to highlight the tendency, in Germany, towards a multi-nodality network, where accessibility can play a fundamental role.     

Risk assessment for organochlorines and organophosphates pesticide residues in water and Sediments from lower Nyando/Sondu‐Miriu river within Lake Victoria Basin,Kenya

The objective of this study was to survey and document pesticide residue levels in the lower Nyando/Sondu‐Miriu catchment areas of Lake Victoria, Kenya, during the dry and rainy seasons of 2009. Water and sediment samples from the Nyando/Sondu‐Miriu Basin were analysed for selected pesticide residues, using gas chromatography equipped with Ni⁶³ and CP‐SIL 8CB‐15m and TSD detectors for organochlorine and organophosphorus pesticide residues, respectively. The findings indicated that banned organochlorines are still being used in the catchment. Dieldrin and p,p′‐DDD were notably higher (P < 0.05) in concentrations than their metabolically formed analogues of aldrin and DDT, respectively. Notably, organophosphorus was below detection levels in water samples, whereas diazinon and malathion were at higher levels in sediment samples. The total residues of DDT, HCH, methoxychlor and endrin generally were below WHO drinking water limits of 2, 2, 20 and 0.01 μg L^?1, respectively, whereas aldrin and dieldrin were above the recommended values of 0.03 μg L^?1. Agricultural activities in the Lake Victoria Basin are influencing accumulation of the pesticide residues in the basin rivers and the lake. The study recommends creation of buffer zones around the natural water bodies to reduce the inflow of pesticides into water bodies. An integrated pest management approach that encourages reduced usage of chemical compounds also should be encouraged.