Evolution of the intensity profile of Cerenkov second-harmonicradiation with propagation distance in planar waveguides

Using coupled mode theory, we have studied the output intensity profile of Cerenkov second-harmonic radiation from planar waveguides as a function of the propagation distance. In particular, we have obtained the variation of the intensity profile taking into account the effect of prism coupling as well as propagation loss, and have shown that the second-harmonic radiation evolves into a beam-like output. Results of the measured intensity profile of the second-harmonic radiation in proton-exchanged planar waveguides in Z-cut LiNbO₃ are also presented that are consistent with the theory     

S-band single-stage EDFA with 25-dB gain using distributed ASE suppression

We propose a novel compact design for a single-stage S-band erbium-doped fiber amplifier, wherein distributed suppression of C-band amplified spontaneous emission is provided by optimized bend loss in a coaxial core fiber. Simulations show that /spl sim/25-dB unsaturated gain over 30-nm bandwidth (1495-1525) nm is achievable with the designed module, using a nominal pump power of 500 mW. The noise figure of the amplifier varies between 4.5 and 8 dB from 1495 to 1525 nm. By proper designing, we have also ensured that the gain ripple over the entire 30-nm bandwidth is 相似文献   

Experimental observation of longitudinal modulation of mode fields in periodically segmented waveguides

We present what is to our knowledge the first experimental observation by fluorescent visualization, of the evolution of the mode field profile in a periodically segmented waveguide. The experimental observations are then compared with the numerical results obtained by a finite-difference beam propagation method. Good agreement between experimental and numerical results is observed.     

Nanoparticles of vanadia–zirconia catalysts synthesized by polyol-mediated route: Enhanced selectivity for the oxidative dehydrogenation of propane to propene

A polyol-mediated route was employed to obtain nanoparticles of vanadia–zirconia (10 nm) and Ti⁴⁺-modified zirconia catalyst for the selective oxidative dehydrogenation reaction of propane to propene. The catalytic activity and selectivity of samples thus prepared were compared with the values for the sample synthesized by the conventional impregnation method. More dispersed amorphous vanadia species on zirconia support could be obtained by polyol method compared to those obtained by conventional impregnation route, as discerned from transmission electron microscopy (TEM) and Raman studies. Raman spectra of samples prepared by polyol method indicated the presence of monovanadate and polyvanadate species on the zirconia support surface, whereas the impregnated sample showed the existence of aggregated vanadia besides mono and polyvanadate species though the vanadia loading was the same on all samples. XPS studies revealed that vanadia existed as both V⁵⁺ and V⁴⁺ in the samples prepared by the polyol method, whereas only V⁵⁺ state was seen in the impregnated sample. The catalysts prepared by polyol method exhibited enhanced selectivity for propene formation compared to the sample prepared by impregnation method. The enhanced selectivity is attributed to the presence of dispersed vanadia species with lower valence state of vanadium. The present results demonstrate that the polyol-mediated synthesis is an efficient method for the preparation of supported vanadia catalysts containing such active species.     

Role of an Isolator in Optimization of Forward Conversion Efficiency in an Er-Doped SFS Source at 1.55 μm

By incorporating an isolator at an appropriate location, it is shown that it is possible to realize an efficient single-pass superfluorescent-doped fiber source with a major fraction of its emitted power in the forward direction. A theoretical model to estimate the performance of such a superfluorescent source (SFS) has been suggested and verified with experiments performed on an erbium-doped fiber in a novel pump bypass SFS configuration. Results on design issues such as optimum location of the isolator, pump power requirements, and spectral characteristics are also presented.     

Platelet-Activating Factor-Receptor Signaling Mediates Targeted Therapies-Induced Microvesicle Particles Release in Lung Cancer Cells

Microvesicle particles (MVP) secreted by a variety of cell types in response to reactive oxygen species (ROS)-generating pro-oxidative stressors have been implicated in modifying the cellular responses including the sensitivity to therapeutic agents. Our previous studies have shown that expression of a G-protein coupled, platelet-activating factor-receptor (PAFR) pathway plays critical roles in pro-oxidative stressors-mediated cancer growth and MVP release. As most therapeutic agents act as pro-oxidative stressors, the current studies were designed to determine the role of the PAFR signaling in targeted therapies (i.e., gefitinib and erlotinib)-mediated MVP release and underlying mechanisms using PAFR-expressing human A549 and H1299 non-small cell lung cancer (NSCLC) cell lines. Our studies demonstrate that both gefitinib and erlotinib generate ROS in a dose-dependent manner in a process blocked by antioxidant and PAFR antagonist, verifying their pro-oxidative stressor’s ability, and the role of the PAFR in this effect. We observed that these targeted therapies induce MVP release in a dose- and time-dependent manner, similar to a PAFR-agonist, carbamoyl-PAF (CPAF), and PAFR-independent agonist, phorbol myristate acetate (PMA), used as positive controls. To confirm the PAFR dependency, we demonstrate that siRNA-mediated PAFR knockdown or PAFR antagonist significantly blocked only targeted therapies- and CPAF-mediated but not PMA-induced MVP release. The use of pharmacologic inhibitor strategy suggested the involvement of the lipid ceramide-generating enzyme, acid sphingomyelinase (aSMase) in MVP biogenesis, and observed that regardless of the stimuli used, aSMase inhibition significantly blocked MVP release. As mitogen-activated protein kinase (MAPK; ERK1/2 and p38) pathways crosstalk with PAFR, their inhibition also significantly attenuated targeted therapies-mediated MVP release. These findings indicate that PAFR signaling could be targeted to modify cellular responses of targeted therapies in lung cancer cells.     

Novel fiber design for flat gain Raman amplification using single pump and dispersion compensation in S band

This paper reports on a novel fiber design that has an inherently flattened effective Raman gain spectrum. Simulations show that gain-flattened broad-band Raman amplification, using a single pump, can be achieved in any wavelength band by suitably choosing the fiber parameters and the pump wavelength. The fiber also has a high negative dispersion coefficient-(380-515) ps/km/spl middot/nm over the operating range of wavelengths-and the shape of the dispersion curve is such that the total link dispersion can be not only compensated but also flattened. Hence, the designed fiber can serve as a lossless, broad-band, dispersion-flattening, and dispersion-compensating module for the S band, wherein lossless operation is achieved using inherently gain-flattened single-pump Raman amplification. The performance characteristics of such a module was modeled taking into account wavelength-dependent splice loss as well as background loss, and it has been shown through simulations that lossless operation with /spl plusmn/0.2-dB gain ripple is achievable over (1480-1511) nm using a single pump. Moreover, dispersion compensation for five spans of transmission in a 10-Gb/s system, over this 32-nm bandwidth in the S band, should be attainable using the proposed design.     

A reliable character for sexing live or dead Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

A new, reliable character is described and illustrated for distinguishing the sexes in adult Rhyzopertha dominica (F.). Both live and dead beetles can be sexed accurately using the method.     

Maximum likelihood approach to image texture and acoustic signalclassification

The authors describe a method of classifying natural textures based on the maximum likelihood parameter estimation technique. The novelty of the technique lies in the use of textural features that are derived from the subbands of a wavelet transformed image via the co-occurrence matrices. A maximum likelihood classifier is designed using a set of training texture samples. Ten different Brodotz (1965) textures have been classified using this procedure with an average classification accuracy of 99.7%. The main emphasis is to apply this technique to the classification of underwater acoustic signals. A time-frequency plot is obtained for each segment of the acoustic signal and then converted to an intensity pattern. The textural classification scheme is then applied to the intensity patterns of the acoustic signals. Eight different underwater acoustic signals have been classified by this procedure with an average accuracy of 99.99%