Study on the potential of farmland soils as non-point sources of nitrogen and phosphorus in Japan.

The amounts of N and P accumulated in farmland soils of 50 cm depth were equivalent to the amount of chemical fertilizer supplied for 50-70 years. The values of N/P of surface soils in farmlands were 1.0-4.3, lower than expected. The median diameter of soil particles in run-off waters was generally less than 10 microm. The mean values of particulate fractions over 1 microm and over 0.22 microm were 19% for N, 27% for P, and 39% for N, 64% for P respectively. Fine particles of soil containing concentrated phosphorus should be carefully monitored as potential sources related to eutrophication.     

A 21-mW 4-Mb CMOS SRAM for battery operation

The authors describe a 21-mW 4-mB CMOS SRAM for the application of memory systems which operate on 3-V batteries. A low active power is achieved by novel circuit technologies. A thin-film transistor (TFT) load memory cell effectively reduces standby current to 0.4 μA. A new multibit test circuit, which permits measurement of access time, is also introduced for a reduction of the test time. The authors describe the characteristics of the TFT memory cell and the improved memory cell design for stable cell operation. The 0.6-μm process technology used to fabricate the 4-Mb SRAM and the chip performance are outlined     

A speaker-independent connected digit recognition systemconcatenating statistically discriminated words

A recognition system for connected digits, which uses a statistical classifier to identify words in speaker-independent continuous speech, is described. The system uses the multiple similarity method, a statistical pattern recognition technique. For evaluating word strings, the system uses a scoring method that is independent of the number of words in the strings. It is derived from the a posteriori probability that a subinterval corresponds to a correct word position, giving a word similarity value. The system evaluates a word string using dynamic programming and a parallel search procedure. Experiments for the contextual effect of the training data set, for validation of the search algorithm, and for a large quantity of unspecified speakers including 40 males and 40 females were performed. For connected digits (unknown word lengths test), the string recognition rates were 90.1%-95.1% for two, three, or four connected digits, where the equivalent word (digit) rates were 97.4%-98.4%     

Enzyme-linked immunosorbent assay for nonylphenol using antibody-bound microfluid filters in vertical fluidic operation

We developed an enzyme-linked immunosorbent assay for an endocrine disrupter, nonylphenol, using a microreactor composed of two reaction vessels stacked vertically through a microfluid filter. The filters constructed by deep X-ray lithography possessed 2100 through-bores (phi40 x 200 microm) in polymethylmethacrylate sheets (phi3 mm), which are appropriate for biochemical reactions. Through the optimization of the immunoassay, nonylphenol was quantitatively detected at the range of 0.1-10 ng/ml.     

Optical tweezers and fluid characteristics of an optical rotator with slopes on the surface upon which light is incident and a cylindrical body

The characteristics of the optical trapping force, optical torque, and viscous drag force for a newly proposed cylindrical optical rotator are analyzed. The optical trapping force and torque are evaluated by use of a ray optics model for both parallel and focused laser beam illumination. The drag force is calculated from computational fluid dynamics to be the sum of the components of both the pressure and the shearing stress on all the surfaces of the rotator. We analyze the rotation rate by balancing the optical torque with the drag force. A cylindrical optical rotator is expected to rotate at a high speed because of its highly efficient generation of optical torque and its small viscous drag force.     

Applications of an extremely short strong-feedback configuration of an external-cavity laser diode system fabricated with GaAs-based integration technology

A composite-cavity laser diode is used to monitor the reflectivity or the displacement of the external-cavity mirror for micromechanical photonics devices. Optical disk bits are read out in the near field from the difference in medium reflectivity with an antireflection-coated laser diode and a photodiode. Microbeam vibration is also detected in the near field from the phase difference with an uncoated laser diode and a photodiode. In both cases the carrier-to-noise ratio is very high (more than 45 dB) because of the lack of mode-hopping noise resulting from the extremely short (less than 3 μm) external-cavity length and strong light feedback. These composite-cavity laser diode microdevices are fabricated on a gallium arsenide substrate to eliminate the need for optical alignment.