Monolithically integrated MEMS mirror array with low electrical interference in wavelength-selective switches

This paper describes the fabrication of a microelectromechanical-system (MEMS) mirror array for a wavelength-selective switch (WSS). The MEMS mirror array, in which a lot of closely spaced adjacent mirrors are electrostatically operated, consists of a MEMS mirrors and a mirror-drive electrodes. In order to reduce electrical interference, comb-shaped ground walls with a high aspect ratio of about 20 are monolithically integrated with the MEMS mirror chip. Further, U-shaped gold electroplating walls are formed in the mirror-drive electrode chip. With these walls, each MEMS mirror successfully operates with low electrical interference.     

Estimation of particle size distribution from cross-sectional particle diameter on the cutting plane

To control highly functional sintered materials, it is necessary to evaluate particle size segregation within materials. In the present study, a new method for estimating particle size distribution is proposed; this method considers the occurrence probability of the cutting diameter. The proper particle size distribution in a particle bed was estimated by calculating a matrix consisting of the occurrence probability and the distribution of particle diameters measured on a cutting plane. The estimated particle size distribution was smoothed using the Phillips–Twomey method. A cavity-filling simulation was carried out to verify the validity of the proposed method using the Distinct Element Method. The particle size distribution estimated by this method correlated well with the actual particle size distribution. The effect of particle size distributions with various geometrical standard deviations on the accuracy of estimated values was also investigated. The accuracy increased as the geometric standard deviation increased, and there was an optimum particle size bin number for a specific particle distribution. It was found that a large bin number and a large number of measured particles were required to obtain a higher accuracy for narrow size distributions.     

Combination of spatio-temporal correction methods using traffic survey data for reconstruction of people flow

Data on people flow has become increasingly important in various fields, including marketing and public services. Although mobile phones enable the user’s position to be located with a certain degree of accuracy from a large number of people and become one of the most promising devise, unwillingness to share related with privacy issues still remain. Therefore, it is also important to establish a practical method for reconstructing people flow from various kinds of existing fragmentary spatio-temporal data, such as public traffic survey data, from a view of complementariness with mobile phone data. In this study, we propose a combination of spatio-temporal correction processes to a previously published method, to generate continuous spatio-temporal people flow data sets at chosen intervals in selected cities. The correction methods include temporal smoothing of departure time using kernel density estimation, network data correction in OpenStreetMap data, and spatial smoothing in geocoding with MODIS data. We also compare the reconstruction accuracy by deriving correlation coefficients for different combinations of correction methods. Such reconstructed people flow data can potentially be used as infrastructure data in various fields, including emergency planning and related events in areas where data collection and real-time awareness are weak.     

Quantum chemical calculation of electron transfer at metal/polymer interfaces

Calculation of contact charging at metal/polymer interfaces were performed by a quantum chemical method (DV-Xa). In the calculation, model clusters with dangling bonds were used. The model clusters showed surface states in the density of states (DOS), the electron transfer occurred at the contact interfaces between polymer and Al. Then, 0.3 nm was a reasonable value as the contact distance in the present simulation.Contact electrifications between PTFE and six metals, such as Pt, Au, Cu, Al, Pb and Ca were simulated. The charge transferred from the metal to PTFE depended on the work function of the metals, and had a gap in range of 4.25–4.28 eV. According to the gap of metals were classified into two groups. If Fermi level of a metal is lower than the lowest unoccupied molecular orbital (LUMO) level of PTFE, the electrons of the metal transfer to the surface state (interface state). Electrons in the other metals with a higher Fermi level move into the conduction band of PTFE.     

Effect of storage on film-formation property of vinylidene chloride-acrylonitrile-methyl acrylate terpolymer latex

Latex prepared from 91 : 5 : 4 wt % vinylidene chloride-acrylonitrile-methyl acrylate monomer mixture by seeded semicontinuous emulsion polymerization was investigated for a change in minimum film-formation temperature (MFFT) during storage, with focus placed on polymer crystallinity in the dispersed state. MFFT rose from 20°C to 32°C, with storage at 20°C for 49 weeks. Infrared absorption of fresh and stored latexes in the dispersed state indicated an increase in absorbance at 1048 cm⁻¹, which is characteristic of a crystalline vinylidene chloride polymer, that correlated with the MFFT rise with storage. This suggested that the MFFT rise with storage was caused by increasing crystallinity of the polymer in the dispersed state. X-ray wide-angle diffraction and infrared absorption of powder polymers obtained by lyophilization of fresh and stored latexes also indicated increasing crystallinity with latex storage. Oxygen gas permeabilities of films coated with fresh and stored latexes were measured. Latex stored for long periods exhibited poor barrier property, indicating that such latex is unsuitable as an industrial barrier coating material for films and papers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 573–579, 1998     

The Ceramide Synthase Subunit Lac1 Regulates Cell Growth and Size in Fission Yeast

Cell division produces two viable cells of a defined size. Thus, all cells require mechanisms to measure growth and trigger cell division when sufficient growth has occurred. Previous data suggest a model in which growth rate and cell size are mechanistically linked by ceramide-dependent signals in budding yeast. However, the conservation of mechanisms that govern growth control is poorly understood. In fission yeast, ceramide synthase is encoded by two genes, Lac1 and Lag1. Here, we characterize them by using a combination of genetics, microscopy, and lipid analysis. We showed that Lac1 and Lag1 co-immunoprecipitate and co-localize at the endoplasmic reticulum. However, each protein generates different species of ceramides and complex sphingolipids. We further discovered that Lac1, but not Lag1, is specifically required for proper control of cell growth and size in Schizosaccharomyces pombe. We propose that specific ceramide and sphingolipid species produced by Lac1 are required for normal control of cell growth and size in fission yeast.     

Rheological properties and some applications for rhamsan and xanthan gum solutions

The rheological properties of solutions of xanthan gum (Kelzan® D) and three rhamsan gums, S-60, S-130 and S-194, are examined. Effects studied include those of temperature, concentration and (for the rhamsan gums) extent of side chain branching. Solutions of greater viscosity and elasticity at most shear rates result as the degree of branching increases. When compared with xanthan gum, S-194 is found to be less temperature sensitive and more stable to excess shear. The use of these polymers in two commercial applications, i.e. coal–water mixtures and timber preservative emulsions, is also examined. Several advantages are identified when rhamsan gums are used instead of xanthan gum in both cases.     

Packaging for a 40-channel parallel optical interconnection modulewith an over-25-Gbit/s throughput

NTT is currently working on developing a high-throughput interconnection module that is both compact and cost effective. The technology being developed is called “parallel inter-board optical interconnection technology”, or “ParaBIT”. The ParaBIT module that has been developed is the first step; it is a front-end module with 40 channels, a throughput of over 25 Gbit/s, and a transmission distance of over 100 m along multimode fibers. One major feature of this module is the use of vertical-cavity surface-emitting laser (VCSEL) arrays as very cost-effective light sources. These arrays enable the same packaging structure to be used for both the transmitter and receiver. To achieve super-multichannel performance, high-density multiport bare-fiber (BF) connectors were developed for the module's optical interface. Unlike conventional optical connectors, these BF connectors do not need a ferrule or spring. This ensures physical contact with an excellent insertion loss (less than 0.1 dB per channel). A polymeric optical waveguide film with a 45° mirror for coupling to the VCSEL and photo-diode (PD) arrays by passive optical alignment was also developed. To facilitate coupling between the VCSEL/PD array chips and the waveguide, a packaging technique was developed to align and die bond the optical array chips on a substrate. This technique is called transferred multichip bonding (TMB); it can be used to mount optical array chips on a substrate with a positioning error of only several micrometers. These packaging techniques enabled ultra-parallel interconnections to be achieved in prototype ParaBIT modules