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Radiation Resistance (radiation + resistance)

Distribution by Scientific Domains

Engineering	70%
Medical Sciences	20%

Selected Abstracts

Radiation resistance of coax-fed rectangular microstrip patch antenna with the use of artificial neural networks

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2002
Shyam S. Pattnaik
Abstract A novel method of using artificial neural networks (ANNS) for the calculation of the radiation resistance of a coax-fed rectangular microstrip antenna is presented in this Letter. The network is trained with the results of three different antennas and tested for the fourth antenna. The tested results are in very good agreement. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 51,53, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10370 [source]

Results of flight demonstration of terrestrial solar cells in space

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2005
Mitsuru Imaizumi
Abstract Radiation resistance of six types of solar cells developed for terrestrial use has been demonstrated in space by the MDS-1 Tsubasa satellite which flew in a geostationary transfer orbit where the radiation environment is severe. Open-circuit voltage and short-circuit current of the cells were monitored for duration of about 400 days after launch. Super radiation tolerance of the CuInGaSe2 solar cell was demonstrated in actual space. Also, most of the cells were determined to have capability or applicability for space use. A comparison of the degradation trend of the flight data with that of ground irradiation test results using the displacement damage dose method demonstrated good agreement, indicating sufficient validity of ground-test techniques and accuracy of the end-of-life prediction. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Promising Functional Materials Based on Ladder Polysiloxanes,

ADVANCED MATERIALS, Issue 15 2008
Qilong Zhou
Abstract Preparation of real ladder polysiloxanes (LPSs), including both oxygen-bridged ladder polysilsesquioxanes (LPSQs) and organo-bridged ladder polysiloxanes (OLPSs), had been a great challenge to polymer chemists from 1960 until the successful synthesis of LPSs via the supramolecular architecture-directed stepwise coupling polymerization (SCP) in the early 1980s. This opened up a new field of LPS-based advanced materials. As key building blocks, LPSs are used to construct a variety of polysiloxanes with special steric configurations and functions, such as mesomorphic LPSs, tubular polysiloxanes (TPs), and pseudo-sieve-plate polysiloxanes (pseudo-SPSs). With excellent temperature and radiation resistance, good solubility, and fine optical and mechanical properties, all these polysiloxanes demonstrate very promising prospects in the advanced materials realm. Here, the synthesis of well-ordered LPSs is presented and features of fishbone-like and rowboat-like liquid crystalline polysiloxanes are discussed. Special emphasis is given to typical applications of LPSs, TPSs, and pseudo-SPSs in the areas of liquid crystal displays, microelectronics packaging, and nonlinear optical materials. [source]

Matching network design using non-Foster impedances

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2006
*Article first published online: 8 FEB 200, Stephen E. Sussman-Fort
Abstract Non-Foster synthesis bypasses the gain-bandwidth limitations of conventional LC matching and achieves superior broadband performance by employing negative circuit elements, which are realized via negative impedance converters. The idea is to construct a negative-image model of an antenna, which cancels the antenna's parasitic reactance and transforms its frequency-dependent radiation resistance to a constant value. Successful implementation of negative-image modeling requires the realization of stable, low-loss negative elements. After a discussion of the basic ideas of non-Foster matching, we present experimental results for broadband, stable, high- Q, grounded negative capacitance. Next, in the first experimental confirmation of non-Foster impedance matching for signal reception, we use a floating negative capacitor to cancel a substantial portion of the reactance of a 6-in. monopole antenna. Over 20,110 MHz, the signal-to-noise ratio improved by up to 6 dB as compared to the same antenna with no matching, or to a lossy-matched blade antenna of twice the size. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006. [source]

Characteristic analysis of reverse-L-shaped microstrip-fed large-bandwidth printed slot antenna

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2002
Yong-Woong Jang
Abstract The characteristics of a reverse-L-shaped microstrip-fed structure is analyzed using the finite difference time domain method, and the characteristics of the proposed antenna are compared with a conventional antenna. The return loss, radiation resistance, and voltage,standing wave ratio in the frequency domain are calculated by Fourier transforming the time domain results. When the proposed feed structure is used, the bandwidth is extended in proportion to the slot width and the radiation resistance has the low value. When the slot width is 16 mm, the experimental bandwidth is approximately 50% (,10 dB , S11) at the center frequency of 2.3 GHz. In addition, the experimental data for the impedance and radiation pattern of the antenna are described. They are in good agreement with the calculated results. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 496,502, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10055 [source]

Printable Yagi antenna with closely spaced elements

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007
Sungkyun Lim
Abstract A two-element, planar Yagi antenna with closely spaced elements is reported. Multiple folding in the driver is used to boost up the low radiation resistance due to the close spacing between the driver and the director. The antenna dimensions are first optimized in wire form and then transferred into a printed version on PET film. A prototype planar monopole Yagi is built and measured at 1 GHz. The maximum realized gain of the antenna on 50-,m PET film is measured to be 9.56 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2106,2109, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22660 [source]

Radiation resistance of coax-fed rectangular microstrip patch antenna with the use of artificial neural networks

Rad51 overexpression rescues radiation resistance in BRCA2-defective cancer cells

MOLECULAR CARCINOGENESIS, Issue 2 2009
Erika T. Brown
Abstract Breast cancers with BRCA2 mutations exhibit DNA repair defects and are particularly sensitive to radiation. BRCA2 interacts with Rad51 in a complex manner involving internal BRC and C-terminal TR2 domains which play a key role in homologous recombination. BRCA2 expression also modulates Rad51 protein levels such that Rad51 protein is relatively decreased in BRCA2-defective cancer cells. This is mediated in part through BRCA2's capacity to protect Rad51 from caspase-3 proteolytic degradation. In order to distinguish between functional and expression related roles for BRCA2 we studied the results of Rad51 overexpression in mouse and human cells with inactivating BRCA2 mutations. The results show that overexpression of wild-type Rad51 partially rescues BRCA2 deficiency but that overexpression of a caspase-3 resistant Rad51 completely complements the BRCA2 defect in radiation responsiveness. These results indicate that Rad51 can compensate for some aspects of a BRCA2 gene defect and suggest that Rad51 expression levels may be an important modifier of the BRCA2 defective genotype. © 2008 Wiley-Liss, Inc. [source]

Space and terrestrial photovoltaics: synergy and diversity,

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2002
Sheila G. Bailey
A historical view of the research and development in photovoltaics from the perspective of both the terrestrial and the space communities is presented from the early days through the 1970s and 1980s, 1990s and beyond. The synergy of both communities, both at the beginning and in the present, and hopefully in the future, are highlighted, with examples of the important features in each program. The space community which was impressed by the light weight and reliability of photovoltaics drove much of the early development. Even today, nearly every satellite and other scientific space probe that has been launched has included some solar power. However, since the cost of these power systems was only a small fraction of the satellite and launch cost, the use of much of this technology in the terrestrial marketplace was not feasible. It was clear that the focus of the terrestrial community would be best served by reducing costs. This would include addressing a variety of manufacturing issues and raising the rate of production. Success in these programs and a resulting globalization of effort resulted in major strides in the reduction of PV module costs and increased production. Although, the space community derived benefit from some of these advances, its focus was on pushing the envelope with regard to cell efficiency. The gap between theoretical efficiencies and experimental efficiencies for silicon, gallium arsenide and indium phosphide became almost nonexistent. Recent work by both communities have focused on the development thin-film cells of amorphous silicon, CuInSe2 and CdTe. These cells hold the promise of lower costs for the terrestrial community as well as possible flexible substrates, better radiation resistance, and higher specific power for the space community. It is predicted that future trends in both communities will be directed toward advances through the application of nanotechnology. A picture is emerging in which the space and terrestrial solar cell communities shall once again share many common goals and, in fact, companies may manufacture both space and terrestrial solar cells in III,V materials and thin-film materials. Basic photovoltaics research, including these current trends in nanotechnology, provides a valuable service for both worlds in that fundamental understanding of cell processes is still vitally important, particularly with new materials or new cell structures. It is entirely possible that one day we might have one solar array design that will meet the criteria for success in both space and on the Earth or perhaps the Moon or Mars. Published in 2002 by John Wiley & Sons, Ltd. [source]

Bcl-2 mediated modulation of vascularization in prostate cancer xenografts,

THE PROSTATE, Issue 5 2009
Yoshihisa Sakai
Abstract PURPOSE We previously demonstrated that Bcl-2 overexpression enhances the radiation resistance of PC-3 human prostate cancer cells and xenografts by inhibiting apoptosis, increasing proliferation, and promoting angiogenesis. To further elucidate the relationship between Bcl-2 expression and the angiogenic potential of PC-3-Bcl-2 cells, tumorigenicity, angiogenesis, and lymphangiogenesis were evaluated and compared in a Bcl-2 overexpressing clone in vitro and in vivo. EXPERIMENTAL DESIGN Human prostate cancer cells over expressing Bcl-2 were studied in vitro and in vivo to determine the angiogenic and lymphangiogenic properties of these cells. RESULTS Increased Bcl-2 expression enhanced the tumorigenicity of prostate cancer xenografts. It also enhanced the expression and secretion of key angiogenic and lymphangiogenic factors that stimulated the synthesis of CD31-positive blood vessels and LYVE-1 positive lymphatics. Specifically, the increased angiogenic and lymphangiogenic potential correlated with increased serum levels of basic fibroblast growth factor (bFGF), interleukin 8 (CXCL8), and matrix metalloproteinase (MMP 9). In vitro analysis demonstrated that Bcl-2 expressing tumor cells secreted bFGF and vascular endothelial growth factor (VEGF) into culture supernatants. Microarray analysis of Bcl-2 expressing PC-3 cells demonstrated increased transcription of genes involved in metabolism, such as interleukins, growth factors, tumor necrosis factors (TNF) family members, and peptidases. CONCLUSIONS Together, these results demonstrate that Bcl-2 can regulate tumoral angiogenesis and lymphangiogenesis and suggest that therapy targeted at Bcl-2 expression, angiogenesis, and lymphangiogenesis may synergistically modulate tumor growth and confirm that Bcl-2 is a pivotal target for cancer therapy. Prostate 69:459,470, 2009. © 2008 Wiley-Liss, Inc. [source]