A simultaneous all-optical frequency upconversion technique using four-wave mixing in a semiconductor optical amplifier (SOA) is experimentally demonstrated for wavelength-division-multiplexing (WDM) radio-over-fiber ...
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A simultaneous all-optical frequency upconversion technique using four-wave mixing in a semiconductor optical amplifier (SOA) is experimentally demonstrated for wavelength-division-multiplexing (WDM) radio-over-fiber applications. Eight WDM optical radio-frequency (RF) signals having the RF frequency of 26.5 GHz are simultaneously generated by mixing eight WDM optical intermediate-frequency (IF) signals having the IF frequency of 2.5 GHz with an optical local oscillator signal of 24 GHz in a single SOA. The power penalty for simultaneous generation of eight WDM optical RF signals at the bit-error rate of 10(-9) is less than 2.7 dB.
Two schemes of photonic frequency upconversion utilizing four-wave mixing in a semiconductor optical amplifier were investigated for radio over fiber applications. Optical radio frequency (RF) signals having a RF freq...
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ISBN:
(纸本)9781457702556
Two schemes of photonic frequency upconversion utilizing four-wave mixing in a semiconductor optical amplifier were investigated for radio over fiber applications. Optical radio frequency (RF) signals having a RF frequency of 26.5 GHz are generated by mixing an optical intermediate frequency signal having a frequency of 2.5 GHz with an optical local oscillator signal having a frequency of 24 GHz using two different schemes. The scheme-1 provided lower receiver sensitivity while the scheme-2 showed higher peak power and polarization immunity.
We have experimentally demonstrated a full-duplex wavelength division-multiplexing-based radio-over-fiber system using all-optical single-sideband (SSB) frequency upconversion and wavelength re-use techniques for broa...
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We have experimentally demonstrated a full-duplex wavelength division-multiplexing-based radio-over-fiber system using all-optical single-sideband (SSB) frequency upconversion and wavelength re-use techniques for broadband optical-wireless access networks. The optical SSB RF signal having the RF frequency of 62.5 GHz is generated by using this all-optical frequency upconverter that consists of an arrayed waveguide grating for optical demultiplexing and a semiconductor optical amplifier for wavelength conversion based on the cross-gain modulation effect. The receiver sensitivity at the bit error rate of 10(-9) is -11.5 and -32.5 dBm for downlink (including air transmission of 1.5 m) and uplink, respectively. The power penalties originating from the fiber chromatic dispersion are negligible after transmission over 25-km standard mode fibers (SMFs) for both downlink and uplink. For the IF wavelengths from 1530 to 1580 nm (covering C-band), the variation of the receiver sensitivity is less than 2.5 dB.
An all-optical frequency upconverter using an optical interleaver and a semiconductor optical amplifier (SOA) has been experimentally demonstrated for radio-oyer-fiber (RoF) applications. An optical radio frequency (R...
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ISBN:
(纸本)9781424460571
An all-optical frequency upconverter using an optical interleaver and a semiconductor optical amplifier (SOA) has been experimentally demonstrated for radio-oyer-fiber (RoF) applications. An optical radio frequency (RF) signal (f(RF)=25 GHz) consisting of an optical carrier and a sideband is generated by mixing an optical intermediate frequency (IF) signal (f(IF)=1 GHz) with an optical local oscillator (LO) signal (f(LO)=24 GHz). The phase noise characteristic of the all-optical frequency upconverter is limited by that of the LO signal source. However, it is degraded due to path imbalance of two optical signal paths, which can be compensated by the use of a delay line. Compensation of the path imbalance by an optimum delay line produces an optimized phase noise of the upconverted RF signal of approximately -98 dBc/Hz at the offset frequency of 10 kHz.
The photoluminescence (PL) of undoped, Si-doped, and Be-doped GaAs nanowires (NWs) grown on Si substrates by molecular beam epitaxy was investigated. PL peaks of the undoped and Be-doped NWs were observed at higher en...
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The photoluminescence (PL) of undoped, Si-doped, and Be-doped GaAs nanowires (NWs) grown on Si substrates by molecular beam epitaxy was investigated. PL peaks of the undoped and Be-doped NWs were observed at higher energies than the bandgap energy of GaAs bulk. According to X-ray diffraction analysis, the blue-shift is attributed to the wurtzite-rich GaAs NW structure. Impurity-related peaks were observed in the undoped NWs and the impurity was Si that diffused via interaction with the adatoms on the Si surface during the growth. A slight bandgap narrowing of the Be-doped GaAs NWs was observed from their PL spectra. The Si-doped NWs showed a very broad PL peak due to a larger density of Si-related defects originating from the heavy doping level. The dependence of the PL peaks of the NWs on temperature was also investigated. (C) 2010 Elsevier Ltd. All rights reserved.
Alternative splicing is a fine-tuned. process known. for generating multiple functional variants front individual genes leading to protein diversity. The immune system utilizes pre-mRNA splicing to expand its gene fun...
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Alternative splicing is a fine-tuned. process known. for generating multiple functional variants front individual genes leading to protein diversity. The immune system utilizes pre-mRNA splicing to expand its gene function. Numerous immunologically relevant genes have been found to undergo alternative splicing, thus revealing a new source of complexity in the immune gene network This review attempts to summarize the general features of alternative splicing and its role in the immune system along with a special focus on the available reports of alternative splicing in cytokines, mainly interleukins and their receptors and their regulatory significance.
The beneficial effects of probiotics have been described in many diseases, but the mechanism by which they modulate the immune system is poorly understood. In this study, we identified a mixture of probiotics that up-...
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The beneficial effects of probiotics have been described in many diseases, but the mechanism by which they modulate the immune system is poorly understood. In this study, we identified a mixture of probiotics that up-regulates CD4(+)Foxp3(+) regulatory T cells (Tregs). Administration of the probiotics mixture induced both T-cell and B-cell hyporesponsiveness and down-regulated T helper (Th) 1, Th2, and Th17 cytokines without apoptosis induction. It also induced generation of CD4(+)Foxp3(+) Tregs from the CD4(+)CD25(-) population and increased the suppressor activity of naturally occurring CD4(+)CD25(+) Tregs. Conversion of T cells into Foxp3(+) Tregs is directly mediated by regulatory dendritic cells (rDCs) that express high levels of IL-10, TGF-beta, COX-2, and indoleamine 2,3-dioxygenase. Administration of probiotics had therapeutical effects in experimental inflammatory bowel disease, atopic dermatitis, and rheumatoid arthritis. The therapeutical effect of the probiotics is associated with enrichment of CD4(+)Foxp3(+) Tregs in the inflamed regions. Collectively, the administration of probiotics that enhance the generation of rDCs and Tregs represents an applicable treatment of inflammatory immune disorders.
Highly selective and low damage etching of the GaAs cap layer on AlGaAs is essential in fabricating GaAs/AlGaAs high electron mobility transistors. The GaAs on AlGaAs was etched using a low energy Cl-2/O-2 neutral bea...
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Highly selective and low damage etching of the GaAs cap layer on AlGaAs is essential in fabricating GaAs/AlGaAs high electron mobility transistors. The GaAs on AlGaAs was etched using a low energy Cl-2/O-2 neutral beam and the Schottky device characteristics fabricated on the exposed AlGaAs were compared with those fabricated after the etching using wet etching and a Cl-2/O-2 ion beam. Using a low energy Cl-2/O-2 ion beam or a Cl-2/O-2 neutral beam, highly selective etching of the GaAs cap layer to AlGaAs similar to wet etching could be achieved through the formation of Al2O3 on the exposed AlGaAs during the etching. When the electrical characteristics of the Schottky devices were compared, the devices fabricated after the etching using the neutral beam showed the best electrical characteristics such as electrical stability, low leakage current, higher barrier height, etc. by showing low damage to the exposed AlGaAs surface.
Calcium-dependent gating of large-conductance calcium-activated potassium (BKCa) channels is mediated by the intracellular carboxyl terminus, which contains two domains of regulator of K+ conductance (RCK). In mammali...
Calcium-dependent gating of large-conductance calcium-activated potassium (BKCa) channels is mediated by the intracellular carboxyl terminus, which contains two domains of regulator of K+ conductance (RCK). In mammalian BKca channels, the two RCK domains are separated by a protein segment of 101 residues that is poorly conserved in evolution and predicted to have no regular secondary structures. We investigated the functional importance of this loop using a series of deletion mutations. We found that the length, rather than the specific sequence at the central region of the segment, is critical for the functionality of the channel. As the length of the loop is progressively shorted, the conductance-voltage relationship gradually shifts toward more positive voltages with a minimum length of 70 amino acids, in an apparent response to increased tension within the loop. Thus, the functional activity of the BKCa channel can be modulated by altering the tension of this loop region.
Cinnamon is one of the most widely used herbal medicines with diverse bioactive effects. However, little evidence has been reported about the potential anti-tumor effects of cinnamon. In vitro and in vivo system, cinn...
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Cinnamon is one of the most widely used herbal medicines with diverse bioactive effects. However, little evidence has been reported about the potential anti-tumor effects of cinnamon. In vitro and in vivo system, cinnamon treatment strongly inhibited the expression of pro-angiogenic factors and master regulators of tumor progression not only in melanoma cell lines but also in experimental melanoma model. In addition, cinnamon treatment increased the anti-tumor activities of CD8(+) T cells by increasing the levels of cytolytic molecules and their cytotoxic activity. In conclusion, cinnamon extract has the potential to be an alternative medicine for tumor treatment. (C) 2009 Elsevier Ireland Ltd. All rights reserved.
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