A light-transmitting two-dimensional photodetector array using a-Sipin photodiodes and poly-Si TFT's integrated on a transparent substrate

A light-transmitting two-dimensional photodetector array (32×32 cells) using amorphous silicon (a-Si) pin photodiodes and polysilicon (poly-Si) thin film transistors (TFT's) integrated on a transparent substrate has been developed for use in a free-space optical switching network. The fabrication and the characteristics of the photodetector array are discussed. With driving circuits and sensing amplifiers, this photodetector array shows a minimum detectable power of -25 dBm and an insertion loss of 0.4 dB for an incident optical beam with a diameter of 550 μm. By monitoring the positions and the states of input optical beams, this photodetector array can be used to control the optical paths in photonic switching systems, such as a 1024-input-port optical concentrator     

Numerical analysis of collinear monopole antennas with coils

Double-band operation (85 and 900 MHz) of a collinear monopole antenna is numerically demonstrated. The antenna consists of three linear wires connected with two coils, and has a height of 67 cm. One coil acts as a phase compensation element to increase the gain and the other as a decoupling element for use in the mobile telephone band.<>     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

Effect of functional group of ferrocene redox substance on the transport properties of newly designed ion exchange membrane prepared from polymer gel

A different newly designed cationic exchange polymer membrane and anionic exchange polymer membrane were introduced, and also the transport properties of these polymeric membranes were investigated in this study. The transport properties of these polymer membranes in contact with ferrocene redox derivatives were estimated by using electrochemical techniques such as cyclicvoltammetry, chronopotentiometry, and chronoamperometry techniques, respectively. The used ferrocene redox substances, which have different functional groups, were (Ferrocenylmethyl) trimethylamonium iodide, FcMA, Ferrocenedimethanol, FcDM, and Ferrocene carboxylic acid, FcCA. It indicated that the performance of a membrane depended on the content of polymer gel, anionic exchange polymer site (20 wt % and 50 wt %) or cationic polymer exchange site (20 wt % and 50 wt %), and the efficiency of the functional groups of cationic and anionic exchange polymer site as well. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water and salt permeability of reinforcement polymer‐gel composite membrane

The charged mosaic polymer membrane (CMM) without reinforcement and the composite charged mosaic polymer membrane (CCMM) with reinforcement were investigated in terms of salt and water transport (permeability). The composite charged mosaic polymer membrane (CCMM) with reinforcement showed a unique transport behavior such as preferential material transport L_p and ω. Water permeability coefficient, L_p and salt permeability coefficient, ω were estimated by taking account of active layer thickness of composite polymer gel. The L_p and ω values of CCMM with reinforcement were larger than those of CMM without reinforcement. On the other hand, the reflection coefficient of CCMM, σ, showed negative value, which suggested preferential material transport to solvent transport. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Analysis of antireflection coatings using the FD-TD method with the PML absorbing boundary condition

A step-index optical waveguide with an antireflection coating is analyzed using the finite-difference time-domain (FD-TD) method combined with the perfectly matched layer absorbing boundary condition (PML-ABC). It is demonstrated that the numerical simulations having a dynamic range over that for the Mur absorbing boundary condition can be obtained for a single-layer coating. The analysis of a double-layer coating reveals the transient behavior of reflected fields.     

Genetic transformation of Vitreoscilla sp

Of all the methods customarily used to transform E. coli we found only electroporation to be effective for transformation of the Gram-negative bacterium Vitreoscilla, yielding 5.10(5) transformants/microgram of plasmid DNA. The conditions used were close to those described for E. coli E. coli plasmids are stably maintained in Vitreoscilla. This is the first report of exogenous DNA transfer in Vitreoscilla which opens the way for the application of recombinant-DNA techniques to study this unique group of organisms.     

An integrated photodetector-amplifier using a-Si p-i-n photodiodesand poly-Si thin-film transistors

The authors propose a photodetector-amplifier circuit consisting of a bridge photodetector circuit and a CMOS differential amplifier, both monolithically integrated on a transparent substrate. A test circuit was fabricated using a-Si p-i-n photodiodes and poly-Si thin-film transistors on a quartz substrate. A clear effect of the differential amplifier was demonstrated in the test circuit. It is shown that the circuit performance can be controlled by changing the bias current of the differential amplifier. With a relatively low bias current on the order of 10^-11 A, the circuit works digitally with output voltages either close to 0 V or V_DD. The power consumption of the circuit is approximately 60 μW, which is low enough for use in two-dimensional arrays     

Single units and conscious vision

Figures that can be seen in more than one way are invaluable tools for the study of the neural basis of visual awareness, because such stimuli permit the dissociation of the neural responses that underlie what we perceive at any given time from those forming the sensory representation of a visual pattern. To study the former type of responses, monkeys were subjected to binocular rivalry, and the response of neurons in a number of different visual areas was studied while the animals reported their alternating percepts by pulling levers. Perception-related modulations of neural activity were found to occur to different extents in different cortical visual areas. The cells that were affected by suppression were almost exclusively binocular, and their proportion was found to increase in the higher processing stages of the visual system. The strongest correlations between neural activity and perception were observed in the visual areas of the temporal lobe. A strikingly large number of neurons in the early visual areas remained active during the perceptual suppression of the stimulus, a finding suggesting that conscious visual perception might be mediated by only a subset of the cells exhibiting stimulus selective responses. These physiological findings, together with a number of recent psychophysical studies, offer a new explanation of the phenomenon of binocular rivalry. Indeed, rivalry has long been considered to be closely linked with binocular fusion and stereopsis, and the sequences of dominance and suppression have been viewed as the result of competition between the two monocular channels. The physiological data presented here are incompatible with this interpretation. Rather than reflecting interocular competition, the rivalry is most probably between the two different central neural representations generated by the dichoptically presented stimuli. The mechanisms of rivalry are probably the same as, or very similar to, those underlying multistable perception in general, and further physiological studies might reveal much about the neural mechanisms of our perceptual organization.