Peptide mimics of a conserved H5N1 avian influenza virus neutralization site

A panel of 52 murine monoclonal antibodies was found to recognize antigenic determinants that had been conserved among till major genetic subgroups of the I ON I avian influenza virus prevalent since 1997. We screened a phage display library for peptides recognized by one such antibody (8H5). We analysed the specificity of 8H5 for reactive peptides presented as fusion proteins of HBc (hepatitis B core protein) and HEV (hepatitis E virus) structural protein, p239. This was then related to the specificity of the native HA (haemagglutinin) molecule by virtue of the capacity of fusion proteins to compete for 8H5 binding with different strains of H5N1 virus and the reactivity of antisera generated against fusion proteins to bind native HA molecules, and to inhibit haemagglutination and arrest infection by the virus. Nine reactive peptides of different amino acid sequences were identified, six of which were also reactive with the antibody in association with HBc and four were in association with p239. Binding occurred with the dimeric form of the four p239-fusion proteins and one of the HBc-fusion proteins, but not with the monomeric form. The HBc-fusion proteins blocked 8H5 binding with four strains of H5N1 influenza virus. Mouse antisera generated against fusion proteins bound to HA molecules, but did not inhibit haemagglutination or arrest H5N1 infection. Our findings indicate that 8H5 recognizes discontinuous sites presented by secondary and possibly higher structural orders ol'the peptides in spatially favourable positions for binding with the antibody, and that the peptides partially mimic the native 8H5 epitopes oil file H5N1 virus.Science and Technology Foundation of Fujian Province [2008Y0059, F2006BA101B06]; Key Project of Chinese Ministry of Education [1081157]; Foundation front Ministry of Science and Technology [2005DC105006

Investigation of the Magnetic Circuit and Performance of Less-Rare-Earth Interior Permanent-Magnet Synchronous Machines Used for Electric Vehicles

The less-rare-earth interior permanent-magnet synchronous machines (LRE-IPMSMs), which have the advantages of high power density, high efficiency, and low cost, are promising candidates for electric vehicles (EVs). In this paper, the equivalent magnetic circuit (EMC) of LRE-IPMSM is established and analyzed to investigate the machine design principles, and then the performance of an optimized machine is analyzed. Firstly, the equivalent magnetic circuits of the LRE-IPMSM are established by taking the saturation effect into consideration. Secondly, the effects of geometric parameters, such as the permanent-magnet (PM) width, the PM thickness, the flux barrier thickness, the flux barrier span angle, and the bridge width, on no-load flux, q-axis flux, and d-axis flux are investigated, respectively. The results calculated by the EMC method and finite-element analysis (FEA) are analyzed and compared, which proves the effectiveness of the EMC method. Finally, an optimized design of LRE-IPMSM obtained by the magnetic circuit analyses is proposed. The electromagnetic performances and mechanical strength of the optimized LRE-IPMSM are analyzed and verified, respectively

Comparison and research on load characteristics of PM in different permanent magnet synchronous machines

PM enable PMSMs to have higher torque-density and power-density, however the machine performance is closely related to its load characteristics. When the armature excitation does not match the load characteristics of the PM and machine, it can lead to demagnetization and performance degradation. By comparing and studying the IPMSM’s and SPMSM’s load characteristics, a more reasonable machine topology of components such as PM can be obtained, and high-performance machines can be designed more efficiently. Based on the material characteristics of the PM, the armature reaction law of different machines and the demagnetization law of the PM at different current angles were analyzed. There are different magnetic field distribution patterns in IPMSM and SPMSM, and their different load characteristics are compared to study the methods for improving the anti-demagnetization ability of PMs based on different machine structures

A Novel Sensorless Control Strategy for Brushless Direct Current Motor Based on the Estimation of Line Back Electro-Motive Force

In this paper, a novel sensorless control strategy based on the estimation of line back electro-motive force (BEMF) is proposed. According to the phase relationship between the ideal commutation points of the brushless direct current motor (BLDCM) and the zero-crossing points (ZCPs) of the line BEMF, the calculation formula of line BEMF is simplified properly and the commutation rule for different positions of the rotor is presented. The estimation error of line BEMF caused by the freewheeling current of silent phase is analyzed, and the solution is given. With the phase shift of the low-pass filter considered, a compensation method using “60°-α” and “120°-α” is studied in this paper to eliminate the error. Finally, the simulation and experimental results show that the rotor-position-detection error is reduced effectively and the motor driven by the accurate commutation signal can work well at low and high speed