A 2D photonic crystal surface-emitting laser using a triangular lattice is developed, and current-injected lasing oscillation is demonstrated. From consideration of the Bragg diffraction condition in the 2D triangular-lattice structure, it is shown that the 2D coupling phenomenon occurs in the structure. As a result of the 2D periodicity of the structure, the longitudinal mode and lateral mode can be controlled, and stable single-mode oscillation is possible over a large 2D area. The lasing mode of the structure is analyzed by calculating the photonic band diagram by the 2D plane-wave expansion method, and we show that four band edges at which the lasing oscillation can occur exist at the Γ point. Current-injected lasing oscillation is successfully demonstrated at room temperature under pulsed conditions. The threshold current density is 3.2 kA/cm2 and the lasing wavelength is 1.285 µm. From the near-field and far-field patterns, it is shown that large-area 2D (diameter 480 µm) lasing oscillation occurs in the device and the divergence angle is very narrow (less than 1.8). We also demonstrate the correspondence between the measured lasing wavelengths and calculated band diagram by comparing the polarization characteristics with the calculated distribution of the electromagnetic field. The results indicate that 2D coherent lasing oscillation occurs due to the multi-directional coupling effect in the 2D photonic crystal. Finally, we show that the polarization patterns of the lasers can be controlled by introducing artificial lattice defects from the theoretical calculation.

OFDM modulation has attracted attention for fourth-generation mobile communication systems and high-speed wireless LANs. However, it has a very serious problem of large peak power. PTS (partial transmit sequences) has been proposed as one solution to this problem. In PTS, the OFDM subcarriers are divided into several clusters, and the phase of each cluster is rotated by a complex weight to minimize the PAPR (peak-to-average power ratio). However, the weight of the phase rotation must be sent to the mobile terminal by using a side information channel. In this paper, we propose two weight estimation methods at the receiver to avoid weight transmission in side information channels. The first method uses pilot signals, while the second is a blind estimation method that changes the weight pattern. We evaluate the performance of these methods by computer simulation.

In this paper, a network dimensioning approach suitable to the Internet is discussed. Differently from the traditional telephone networks, it is difficult to guarantee QoS for end-users even in a statistically sense due to an essential nature of an end-to-end communication architecture in the Internet. We should therefore adopt another approach, based on the traffic measurement. In the approach, the traffic measurement is performed for monitoring the end-to-end QoS. Then, the network adaptively controls the link capacities to meet the user's QoS demands. For this purpose, the underlying network should support such a capability that the link capacities can be flexibly reused. With the WDM network as an underlying network, an example scenario for network provisioning is finally illustrated.

This paper studies security of Feistel ciphers with SPN round function against differential cryptanalysis, linear cryptanalysis, and truncated differential cryptanalysis from the "designer's standpoint." In estimating the security, we use the upper bounds of differential characteristic probability, linear characteristic probability and truncated differential probability, respectively. They are useful to design practically secure ciphers against these cryptanalyses. Firstly, we consider the minimum numbers of differential and linear active s-boxes. They provide the upper bounds of differential and linear characteristic probability, which show the security of ciphers constructed by s-boxes against differential and linear cryptanalysis. We clarify the (lower bounds of) minimum numbers of differential and linear active s-boxes in some consecutive rounds of the Feistel ciphers by using differential and linear branch numbers, Pd, Pl, respectively. Secondly, we discuss the following items on truncated differential probability from the designer's standpoint, and show how the following items affect the upper bound of truncated differential probability; (a) truncated differential probability of effective active-s-box, (b) XOR cancellation probability, and (c) effect of auxiliary functions. Finally, we revise Matsui's algorithm using the above discussion in order to evaluate the upper bound of truncated differential probability, since we consider the upper bound of truncated differential probability as well as that of differential and linear probability.

For several years, more and more people are joining the Internet and various kind of packets (so called transaction-, block-, and stream-types) have been transmitted in the same network, so that poor network conditions cause loss of the stream-type data packets, such as voices, which request smaller transmission delay time than others. We consider a switching node (router) in a network as an N-series M/G/1-type queueing model and have mainly evaluated the fluctuation of packet delay time and end-to-end delay time, using the two moments matching method with initial value, then define the delay jitter D of a network which consists of jointed N switching nodes. It is clarified that this network is not suitable for voice packets transmission media without measures.

In functional brain images obtained by analyzing higher human brain functions using functional magnetic resonance imaging (fMRI), one serious problem is that these images depict false activation areas (artifacts) resulting from image-to-image physiological movements of subject during fMRI data acquisition. In order to truly detect functional activation areas, it is necessary to eliminate the effects of physiological movements of subject (i.e., gross head motion, pulsatile blood and cerebrospinal fluid (CSF) flow) from fMRI time series data. In this paper, we propose a method for eliminating artifacts due to not only rigid-body motion such as gross head motion, but also non-rigid-body motion like the deformation caused by the pulsatile blood and CSF flow. The proposed method estimates subject movements by using gradient methods which can detect subpixel optical flow. Our method estimates the subject movements on a "pixel-by-pixel" basis, and achieves the accurate estimation of both rigid-body and non-rigid-body motion. The artifacts are reduced by correction based on the estimated movements. Therefore, brain activation areas are accurately detected in functional brain images. We demonstrate that our method is valid by applying it to real fMRI data and that it can improve the detection of brain activation areas.

At present, the global Internet consists of many ASes. Each AS pays a pre-determined connection fee to another AS for connecting its network with that AS's network. The connection fee type charging may be rational in case of transferring the best-effort type traffic. However, usage charging is necessary to transferring the resource guaranteed type traffic such as the Intserv traffic and the Diffserv traffic. In this case, each AS pays a per-flow fee to another AS every time it routes a flow into another AS. The per-flow fee paid by each AS becomes a part of the cost for that AS. Thus, each AS needs to select a route with the lowest price to improve its own profit. In this paper, we call such an inter-AS routing scheme a price-based inter-AS routing scheme. When each AS has a request to route an inter-AS flow, it can select an inter-AS route with the lowest price to improve its own profit by this routing scheme. Cost-dependent pricing scheme is suitable for the price-based inter-AS routing scheme because it can reduce frequency of price information exchange between ASes. However, in the cost-dependent pricing scheme, profit in each AS depends on the distribution of path costs in that AS. Generally, ASes with narrow ranges of path costs cannot obtain sufficient profits compared to ASes with wide ranges of path costs. Thus, we propose a routing policy for ASes with narrow ranges of path costs to improve their profits efficiently and evaluate its effect using a simple routing model.

This study attempts to demonstrate that activated leukocytes are involved in vascular shut down effect (VSD) in photodynamic therapy (PDT). Hydrogen peroxide (H2O2), a reactive oxygen specie (ROS) that is found in monocytes, was visualized under a confocal laser scanning microscope, and ROS formation was quantified by fluorescence image analysis. The fluorescence intensity was expressed as a gray level graded from 0 to 255. Only the fluorescence derived from monocytes that had ZnCP-III incorporated and were irradiated with an HeNe laser caused increases in the fluorescence distribution over time, while no change of distribution was observed in three other conditions (only Zn CP-III added, only HeNe laser irradiation, or non-treated). The result indicates that the photochemical reaction induced by excitation of a photosensitizer, and ROS was derived from the reaction-stimulated monocytes. The activated monocytes generated ROS themselves and H2O2 was visualized by the DCFH fluorescence method. In conclusion, the result clearly shows that activated monocytes are involved in the VSD effect.

Progress on a single wavelength channel OTDM terabit/s transmission is described. In particular, we focus on 1.28 Tbit/s OTDM transmission over 70 km which we realized recently. A pre-chirping technique using a high speed phase modulator is emphasized to simultaneously compensate for third- and fourth-order dispersion. The input pulse width was 380 fs, and the pulse broadening after a 70 km transmission was as small as 20 fs. All 128 channels time-division-demultiplexed to 10 Gbit/s had a bit error rate of less than 110-9, in which we employed a lot of new technique for pulse generation, dispersion compensation and demultiplexing. These techniques help pave the path for OTDM technology of the 21 century.

In Vivo Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) can now be used to elucidate and investigate major nerve pathways in the brain. Nerve pathways are constructed by a) calculating a continuous diffusion tensor field from the discrete, noisy, measured DT-MRI data and then b) solving an equation describing the evolution of a fiber tract, in which the local direction vector of the trajectory is identified with the direction of maximum apparent diffusivity. This approach has been validated previously using synthesized, noisy DT-MRI data. Presently, it is possible to reconstruct large white matter structures in the brain, such as the corpus callosum and the pyramidal tracts. Several problems, however, still affect the method's reliability. Its accuracy degrades where the fiber-tract directional distribution is non-uniform, and background noise in diffusion weighted MRIs can cause computed trajectories to jump to different tracts. Nonetheless, this method can provide quantitative information with which to visualize and study connectivity and continuity of neural pathways in the central and peripheral nervous systems in vivo, and holds promise for elucidating architectural features in other fibrous tissues and ordered media.

A new objective speech quality measure, Bark Coherence Function is presented. The Coherence Function was used for evaluating the non-linear distortion of low-to-medium rate speech coders. However, it is not well suited for quality estimation in modern speech transmission, especially, CDMA mobile communication system. In the proposed method, Coherence Function is newly defined in psycho-acoustic domain as the cognition module of perceptual speech quality measure and evaluates the perceptual non-linear distortion of mobile system. The experimental results showed that the proposed method has good performance over CDMA PCS and digital cellular system.

Human tissues conduct electricity about as well as semiconductors. However, there are large differences between tissues which have recently been shown to be determined mainly by the structure of the tissue. For example, the impedance spectrum of a layered tissue such as skin is very different to that of the underlying tissues. The way in which the cells are arranged and also the size of the nucleus are both important. Some of the recent developments in measurement and modelling techniques are described and the relationship between tissue structures and impedance spectra is outlined. The illustrations and examples look at the effect of premalignant changes on localised impedance spectra measured from cervical tissues. Electrical Impedance Tomographic measurements on lung tissue are used to show the maturational changes of lung structure in neonates. The conclusion contains some speculation as to what further research outcomes might occur over the next few years.

In this paper, we propose a method to reconstruct current distributions in the human brain from neuromagnetic measurements. The proposed method is based on the weighted lead-field synthetic (WLFS) filtering technique with the weighting factors calculated from the results of previous source space scanning. In this method, in addition to the depth normalization technique, weighting factors of the WLFS are determined by the cost values previously calculated based on the multiple signal classification (MUSIC) scan. We performed computer simulations of this method under noisy measurement conditions and compared the results to those obtained with the conventional WLFS method. The results of the simulations indicate that the proposed method is effective for the reconstruction of the current distributions in the human brain using magnetoencephalographic (MEG) measurements, even if the signal-to-noise ratio of the measured data is relatively low. We applied the proposed method to the magnetoencephalographic data obtained during a mental image processing task that included object recognition and mental rotation operations. The results suggest that the proposed method can extract the neural activity in the extrastriate visual region and the parietal region. These results are in agreement with the results of previous positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies.

When a randomized algorithm elects a leader on anonymous networks, initial information (which is called in general initial condition in this paper) of some sort is always needed. In this paper, we study common properties of initial conditions that enable a randomized algorithm to elect a leader. In the previous papers, the author introduced the notion of transformation between initial conditions using distributed algorithms. By using this notion of transformation, we investigate the property of initial conditions for the leader election. We define that an initial condition C is p(N)-complete if there exists some randomized algorithm that elects a leader with probability p(N) on any size N network satisfying C. We show that we can divide p(N)-completeness into four types as follows. 1. p(N)=1: For any 1-complete initial conditions, there exists a deterministic distributed algorithm that can compute the size of the network for any initial information satisfying the initial condition. 2. inf p(N) >0: For any p(N)-complete initial conditions with inf p(N) >0, there exists a deterministic distributed algorithm that can compute an upper-bound for the size of the network for any initial information satisfying the initial condition. 3. inf p(N) converges to 0: The set of p(N)-complete initial conditions varies depending on the decrease rate of p(N). 4. p(N) decreases exponentially: Any initial condition is regarded as p(N)-complete.

We fabricated ultrafast nonlinear optical films of squarylium J-aggregates and studied their properties including the absorption spectrum, the refractive index, the third-order nonlinear optical coefficients, the extent of absorption saturation, and the recovery of absorption saturation. The transmittance of the film was increased by 30% due to absorption saturation at a pump energy of several hundreds fJ/µm2/pulse. The half decay time constant of absorption saturation was found to be approximately 100 fs for off-resonant excitation. Two-dimensional demultiplexing was demonstrated using the squarylium film as a switching material. From a train of 8 optical pulses with 100 fs duration and 1 ps interval corresponding to a bit rate of 1 Tbps, 24 spatially resolved spots were obained.

A technique was developed to reconstruct the cross-sectional image of the absorption distribution in a diffuse medium using backscattered light. In this technique, we illuminate an object with an ultra-short pulse, and measure the time-resolved pulse shape of the light backscattered from the object. The absorption distribution of the scattering object can be estimated using the propagation-path distribution of photons at each detection time and the optical impulse response of backscattered light. In a simulation, the effectiveness of this technique was verified in the cases of a layered absorber and a three dimensional absorber. The nonlinear relationship between the depth of the probing region and the propagation time was clarified. The accuracy of the image reconstruction was significantly improved by the aperiodic sampling of the backscattered impulse response according to the nonlinear relation. The feasibility of the proposed technique was verified in the experiment with a model phantom.

Confocal laser scanning microscope (CLSM) is capable of delivering a high axial resolution, and with this instrument even thin layers of cells can be imaged in good quality. Therefore, intracellular uptake and distribution properties of photosensitizer zinc coproporphyrin III tetrasodium salt (Zn CP-III) in human lung small cell carcinoma (Ms-1) were examined by using CLSM. In particular, the uptake of Zn CP-III in cytoplasm, plasma membrane, and nucleus was individually evaluated for the first time from fluorescence images obtained by CLSM. The results show that the Zn CP-III content in three cellular areas correlates with extracellular Zn CP-III concentration and time of incubation with Zn CP-III. Furthermore, it was found that the cytoplasmic fluorescence was approximately two times higher than that in the nucleus under all uptake conditions. In addition, cellular accumulation of Zn CP-III was compared with photodynamic cytotoxicity. The photocytotoxicity was to a great extent dependent on the uptake of the photosensitizer. The damaged site of Ms-1 cells induced by photodynamic therapy was plasma membrane. However, the content of Zn CP-III accumulated in cytoplasm was the highest among the three areas, implying that, besides the direct damage on plasma membrane, an oxidative damage to cellular component arose from the cytoplasmic Zn CP-III may also play an important role in photocytotoxicity. The quantitative information obtained in this study will be useful for further investigation of the photocytotoxicity as well as the uptake mechanism of photosensitizer.

We applied control theory to nerve-muscle in order to model and systematize the muscle system. The association between nerve stimulation frequencies and electromyogram (EMG) amplitude was studied in rat nerve-muscle under normal and hypokalemic conditions. From these results, we modeled the nerve-muscle and simulated frequency response from the nerve-muscle system which can be expressed as a closed loop transfer function.

Space-variant approaches subject to local image characteristics are useful in practical image restoration because many natural images are nonstationary. Motivated by the success of denoising approaches in the wavelet domain, we propose a region-adaptive restoration approach which adopts a wavelet denoising technique in flat regions after an under-regularized constrained least squares restoration. Experimental results verify that this approach not only improves image quality in mean square error but also contributes to ringing reduction.

Very reliable mode-locked semiconductor lasers have been developed. These devices provide high signal-to-noise ratio optical clock pulses of a few picoseconds temporal width in the 1.5-micrometer wavelength region. Potential applications of these lasers for high-bit-rate optical communication systems operating at over 40 Gbps including all-optical signal processing, and for very high-speed measurement systems are described.