A Systematic Investigation on Diffraction Characteristics of Dielectric Periodic Structure with Arbitrary Grating Profiles

Wave diffraction characteristics of dielectric periodic structures with arbitrary grating profiles are systematically investigated for TE and TM mode polarization by an effective engineering method, which combines the staircase approximation with the rigorous mode matching procedure. The variations of the diffraction with the frequency and incident angle for the periodic structures with different grating profiles, such as rectangle, sinusoid, triangle, trapezoid, increasing cosine, semi-ellipse and semi-circle are systematically and comparatively studied. The effectiveness and accuracy of the present method are verified by the results given in the literature.     

Suboptimal dual adaptive control for blood pressure management

Presents a new approach for adaptive control of blood pressure using vasoactive drugs. The idea is to use an adaptive controller that incorporates the concept of duality in the sense of Feldbaum (1965) and to consider the cost functional M-steps ahead in time. The dual property means that the control signal is chosen in such a way that estimation of the model parameters and regulation of the output signals are optimally balanced. Extensive computer simulations for different values of M shows that the sample mean of the achieved cost tends asymptotically to a limiting value while the variance is reduced. The proposed suboptimal adaptive controller has also an improved transient response when compared to a certainty equivalent controller     

The role of mex-gene products in antibiotic extrusion in Pseudomonas aeruginosa

The antibiotic extrusion machinery in Pseudomonas aeruginosa is assembled from the mex-operon encoded proteins, OprM and MexA-MexB, connecting the outer and inner membranes. To envisage the role of these proteins in antibiotic extrusion and resistance, we employed the gene replacement technique to construct mutants deficient in mexA, mexB, or oprM, and all possible combinations of these genes. Using the Southern and the Western blotting methods, we confirmed that only the target genes were disrupted. All the mutants deficient in OprM exhibited a 4 to 16 times higher susceptibility against quinolone antibiotics, chloramphenicol, and gentamicin than the parent strain. The mutants deficient in MexA or MexB or both MexA and MexB were only 2 to 4 times more susceptible to these antibiotics than the parent strain. All the mutants lacking MexA, MexB, or OprM showed stereospecific hypersusceptibility to beta-lactam antibiotics than the parent strain. However, the extent of susceptibility to each beta-lactam was comparable among the mutants. Strains lacking OprM accumulated the highest level of ciprofloxacin among all these isogenic strains. The strains lacking either MexA or MexB accumulated lower levels of ciprofloxacin than the mutant lacking OprM, but the levels were still higher than in the parent strain. The results are consistent with the antibiotic susceptibility of these strains. These results suggest that the extrusion of antibiotics occurs most efficiently with a whole assembly of MexA/B-OprM, but it remains a possibility that OprM interacts with a putative inner membrane pump(s).     

Photoviscoelastic Stress Analysis near Contact Regions under Complex Loads

This study discusses several types of contact, involving compression andsliding, between a time-dependent material and a rigid body. Itdemonstrates a useful application of a new hybrid method forphotoviscoelastic stress analysis under non-proportional loadingconditions, in which the principal axes of stress, strain, andbirefringence are not aligned with each other. Using a computer-aidedimage processing technique, the distribution of fringe order andbirefringent principal axes in the vicinity of the contact surface areevaluated from a few photoviscoelastic images through a plane polariscopeby using the well known diagonal summation theorem. The variation of theprincipal stress and/or strain differences as well as their directions areeasily obtainable over a wide time range by use of the opticalconstitutive equations of photoviscoelasticity and the characteristicmaterial properties functions.     

A multistage suboptimal dual controller using optimal predictors

This work concerns the control of stochastic systems with unknown and randomly time-varying parameters. Cost functions which consider the sum of output variances up to M steps ahead in time are adopted in the optimization of the control performance. Optimal predictors are used to replace the future outputs which are needed in the solution of the optimization problem. The consequences of this simplification are investigated. A formula is obtained for the computation of the control signal in the case of M-steps-ahead optimization. The relationships between the controller presented here and other classical suboptimal dual controllers are analyzed. Simulation results illustrate the actual performance of the new controller     

Timing of N fertilization on N2 fixation, N recovery and soil profile nitrate dynamics on sorghum/pigeonpea intercrops on Alfisols on the semi-arid tropics

Cropping systems and fertilizer management strategies that effectively use applied nitrogen (N) are important in reducing costs of N inputs. We examined the effect of time of N application on dry matter (DM) and grain yield (GY), N accumulation, the N budget in crop from soil, fertilizer and atmosphere, and the fertilizer N use efficiency (estimated by the conventional difference method, and the direct ¹⁵N recovery by the crops), in a sorghum/pigeonpea intercropping system on an Alfisol (Ferric Luvisols (FAO); or Udic Rhodustalf (USDA) in India. Fertilizer N was applied at planting (basal) and at 40 days after sowing (delayed). Nitrogen was applied only to the sorghum rows in the intercropping treatment. Nitrogen derived from air (N_dfa) was estimated by the¹⁵ N natural abundance method, and N derived from fertilizer (N_dff) was estimated by the ¹⁵N isotope dilution method. Delaying N fertilization till 40 days after sowing (DAS), rather than applying at sowing increased DM and GY of the sorghum, but not of pigeonpea. Delaying N fertilization to sorghum for 40 days significantly (p<0.001) increased ¹⁵N recovery in shoot from 15 to 32% in sole crop, and from 10 to 32% in intercrop. Similarly, there was a significant (p<0.001) increase in N recovery (by the difference method) from 43 to 59% in sole crop and from 28 to 71 % in intercrop sorghum. Fertilizer N recovery by sole crop pigeonpea (14%) was higher than intercrop pigeonpea (2–4%). Pigeonpea fixed between 120–170 kg ha-¹ of atmospheric N throughout the cropping season. Although there was a marked difference in nitrate-N (N0₃-N) concentrations between basal and delayed treatments at planting, no difference was observed in N0₃-N concentrations in soil solution between the treatments at 40 DAS. Our data on N accumulation by plants showed that the rate of N depletion or disappearance from the soil solution was 2–3 times faster than N accumulation by plants, suggesting that an appreciable amount of N0₃-N would disappear from soil solution in the top soil without being utilized by crops during the initial growth stage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Lens design for surface wave applications

A new type of lens is proposed which is effective for surface waves on dielectric slabs at millimetre wavelengths. The lens consists of two identical metallic plates of double convex shape which sandwlch the dielectric slab between them. It is demonstrated that a periodic sequence of the lenses can guide surface beam waves efficiently.     

Photoelectrochemical properties of SrFeNb oxides having perovskite structure

Photoelectrochemical properties of Sr₂FeNbO₆, Sr_1.9Fe_1.1NbO_6?x and Sr₃FeNb₂O₉ having the perovskite structures were investigated using sintered pellets to determine the energy gap and the flat-band potential and to evaluate the electrochemical stability against the anodic decomposition. The energy gap determined was 1.9 eV for Sr₃FeNb₂O₉ and 2.3 eV for both Sr₂FeNbO₆ and Sr_1.9Fe_1.1NbO_6?x. The flat-band potential of these materials was found to be ca. 0.1 V positive of the reversible hydrogen electrode in measured solutions. The onset potential of anodic photocurrents did not coincide with the flat-band potential, however, being more positive than that and varied with the kind of redox electrolyte chosen. Probable causes for this phenomenon are briefly discussed.     

High-speed ASK transceiver based on the NRD-guide technology at60-GHz band

A new type of high-speed amplitude shift-keying (ASK) transceiver has been developed in an integrated manner at 60 GHz by using the nonradiative dielectric waveguide (NRD-guide) technology. An emphasis is placed on the high-speed performance of the newly developed ASK modulator. The modulator uses a Schottky barrier diode (SBD), which has higher switching speed than a p-i-n diode. In addition, the operation principle of it is different from that of the conventional p-i-n diode modulator. A pair of NRD-guide transceivers have been fabricated and 400-Mb/s data-transmission test has been carried out successfully by using them