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42 results on '"Wong, T.P."'

2. A wide bandwidth and wide beamwidth CDMA/GSM base station antenna array with low backlobe radiation

Author

Wong, T.P. and Luk, K.M.

Subjects
Antenna arrays -- Design and construction, GSM (Global System for Mobile Communications) -- Analysis, CDMA technology -- Analysis, GSM, Code Division Multiple Access technology, Business, Electronics, Electronics and electrical industries, Transportation industry
Abstract

A wide bandwidth and wide beamwidth L-probe-fed patch antenna array with a novel design of grounded structure is proposed and tested. The antenna is made of stacked patches supported by plastic screws. The patches are proximity fed via L-shaped probe. By cutting slots in two vertical side walls of a box-shaped grounded structure, an impedance bandwidth larger than 20% (SWR < 1.5), an H-plane beamwidth over 90[degrees], and much reduction in backlobe radiation can be obtained. Details of the proposed antenna, simulation, and experimental results are presented and discussed. Index Terms--Backlobe reduction, base station, L-probe-fed, wideband, wide beamwidth.

Published
2005

8. A wideband L-Probe patch antenna array with wide beamwidth

Author

Wong, T.P. and Luk, K.M.

Subjects
Antennas (Electronics) -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

The design and characteristics of a wide-beamwidth, wide-bandwidth patch antenna fed by an L-shaped probe is presented. The novelty in this design is the incorporation of a folded patch with a U-shaped cross section, the dimensions of which can be optimized to achieve an impedance bandwidth of 20% (SWR < 1.5) and a H-plane beamwidth of 103[degrees]. The antenna finds application as a cellular base station antenna covering both CDMA and GSM bands from 824-9611 MHz. Index Terms--L-Probe, wide beamwidth, wide hand.

Published
2003

27. Activation of PI3-Kinase Is Required for AMPA Receptor Insertion during LTP of mEPSCs in Cultured Hippocampal Neurons

Author

Man, Heng-Ye, primary, Wang, Qinhua, additional, Lu, Wei-Yang, additional, Ju, William, additional, Ahmadian, Gholamreza, additional, Liu, Lidong, additional, D'Souza, Sandra, additional, Wong, T.P, additional, Taghibiglou, C, additional, Lu, Jie, additional, Becker, Larry E, additional, Pei, Lin, additional, Liu, Fang, additional, Wymann, Matthias P, additional, MacDonald, John F, additional, and Wang, Yu Tian, additional

Published
2003
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34. Expression of sperm Ca2+‐activated K+channels in Xenopusoocytes and their modulation by extracellular ATP

Author

Chan, H.C, Wu, W.L, Sun, Y.P, Leung, P.S, Wong, T.P, Chung, Y.W, So, S.C, Zhou, T.S, and Yan, Y.C

Abstract

Ionic fluxes across the sperm membrane have been shown to be important in the initiating process of sperm activation and gamete interaction; however, electrophysiological investigation of the ion channels involved has been precluded by the small size of the sperm, especially in mammalian species. In the present study sperm ion channels were expressed in Xenopusoocytes by injection of RNAs of spermatogenic cells isolated from the rat testes. The RNA‐injected oocytes responded to ATP, a factor known to regulate sperm activation, with the activation of an outwardly rectifying whole‐cell current which was dependent on K+concentrations and inhibitable by K+channel blockers, charybdotoxin (CTX) and tetraethylammonium (TEA). The ATP‐induced current could be mimicked by a Ca2+ionophore but suppressed by a Ca2+chelator applied intracellularly, indicating a Ca2+dependence of the current. Single‐channel measurements on RNA‐injected oocytes revealed channels of large conductance which could be blocked by CTX and TEA. Co‐injection of germ cell RNAs with the antisense RNA for a mouse gene encoding slowpoke‘Maxi’ Ca2+‐activated K+channels resulted in significant reduction of the ATP‐ and ionomycin‐induced current. The expression of the ‘Maxi’ Ca2+‐activated K+channels in sperm collected from the rat epididymis was also confirmed by Western blot analysis. These results suggest that sperm possess Ca2+‐activated K+channels which may be involved in the process of sperm activation.

Published
1998
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36. LOCALIZATION AND DISTRIBUTION OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE IN THE RAT EPIDIDYMIS

Author

LEUNG, P.S, WONG, T.P, WONG, P.Y.D, and CHAN, H.C

Abstract

Previous investigation has provided evidence for the control of electrogenic chloride secretion by pituitary adenylate cyclase-activating polypeptide (PACAP) across the rat epididymal epithelium using electrophysiological measurement of transepithelial transport in cultured epididymal system. Hence, it suggests that epididymal and sperm functions are subject to control by a local PACAP system in the rat epididymis. In the present study, localization and distribution of PACAP in the rat epididymal duct was studied by an indirect immunofluorescence technique in conjunction with confocal laser scanning microscopy. Immunoreactivity for PACAP was found in all regions of the epididymal duct. However, the intensity of immunoreactivity for PACAP was stronger in the caput and corpus regions when compared to that of the cauda epididymidis. Much weaker immunostaining for PACAP, as compared to those found in other regions, was observed in the cauda epididymidal tubules which are in close proximity to the vas deferens. No immunoreactivity for PACAP was found in epididymal spermatozoa. Together with the previous finding, the present results suggest that PACAP may exhibit a regional difference in its expression along the epididymal duct and it may act in a paracrine or autocrine fashion in the regulation of epididymal chloride secretion and hence fluid secretion, thus regulating epididymal and sperm functions along the epididymal duct.

Published
1998
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