bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical mechanisms of chaos in a third‐order autonomous circuit family with a diode
Authors: Inaba Naohiko , Saito Toshimichi
Published: July 2007

The physical mechanism of chaos arising in a third‐order autonomous circuit family containing a diode is discussed in relation to the variation of the oscillation frequency of the circuit. The family to be studied is negative‐resistance LC oscillators containing a nonlinear inductance made of two coils and one diode. When the ratio of the two coils is large, the oscillation frequency of the circuit varies significantly by the on‐off operation of the diode and the resulting “folding” causes chaos.

If the diode is considered a switch, the circuit equation is represented by a form in which the linear ordinary differential equations with significantly different oscillation frequencies are switched to each other. The meaning of the folding becomes clear even in the equation. By means of this and the exact one‐dimensional Poincaré mapping, the generation of chaos is explained clearly and rigorously.
Determination of the number of sinusoidal signals in AR spectral estimation
Authors: Tsuji Hiroyuki , Ohmori Hiromitsu , Sano Akira
Published: July 2007

In carrying out the AR spectral estimation of observed signals consisting of the sum of sinusoidal signal and white noise, since at low SNR many more false peaks occur than the number of sinusoids, a method which uses the eigenvalue decomposition of the correlation matrix to adopt only as many eigenvalues as the number of sinusoids, discarding the rest, is very effective. However, if the number of signals is unknown, how the discarding of eigenvalues should be determined becomes an important problem.

In this paper, to select an appropriate number of eigenvalues of the correlation matrix of the observed data, a multiple number of adjustable parameters is introduced to square the prediction error and, by determining them optimally, determine the number of eigenvalues.

Two new methods are proposed. The first method decides the truncation number of eigenvalues so that the Bayes information criterion with a priori distribution is minimized. The decision criterion is derived and its properties are investigated. The second method determines the number of sinusoids by computing adjustable parameters so that the AR spectrum of a given rank is the closest to the true AR model representing the sinusoidal signal model approximately, that is, the MSE criterion is minimum.

Finally, the effectiveness of the authors' methods are investigated through numerical examples.
A new FIR switched‐capacitor circuit for high‐frequencies with low‐power consumption (parallel cyclic‐type circuit)
Authors: Hirata Yoshinori , Takahashi Nobuaki , Kato Kyoko , Kikui Toshiharu , Takebe Tsuyoshi
Published: July 2007

The high‐frequency performance of switched‐capacitor filters is bounded mainly by the finite gain bandwidth product of operational amplifiers. In this paper, the effects of finite gain bandwidth product of operational amplifiers on the performance of FIR (transversal) filters using such amplifiers as delay elements (canonical circuit) is analyzed. Next, a new low‐power consumption FIR switched‐capacitor circuit for high frequencies, which we call a parallel cyclic‐type circuit (PCTC), is proposed. The proposed circuit does not use operational amplifiers as delay elements. Instead, switches and capacitors are used for both the delaying and the weighting operations.

We present a basic circuit using subblocks, a circuit with reduced number of capacitors, and a modified circuit having plural operational amplifiers for higher‐frequency use. We then show the design of a fourthorder FIR filter employing PCTC. Under the condition that sampling frequency is one‐half of unity gain frequency of operational amplifier, computer simulations of fourth‐order transversal switched‐capacitor filters with canonical circuit and that with parallel cyclic‐type circuit are performed and the experimental results of these circuits using discrete components are also given. Both demonstrate that the parallel cyclic‐type circuit has significantly better performance than the canonical circuit.
Development of a basic software which serves redundant input devices
Authors: Koyama Satoshi
Published: July 2007

Several input/output (I/O) devices should be prepared for a computer user, and its is important that the user be able to choose a suitable one. The author developed an additional basic software which serves redundant input devices: keyboard, mouse, touch‐screen, and other external input devices. The user may operate any of these devices as desired. This software will establish computer‐accessibility for some types of handicapped individuals and will be useful in developing user‐friendly programs. It should also be mentioned that this software is useful in constructing computer‐assisted learning systems which accept concurrent operation.
Student model and its recognition by hypothesis‐based reasoning in ITS
Authors: Matsuda Noboru , Okamoto Toshio
Published: July 2007

This paper describes a framework to infer a student's misconception from observed errors during problem‐solving processes. A human teacher can generate hypotheses about reasons for an error by observing a student's problem‐solving process. The teacher is also able to identify a student's misconception during the process of verifying these hypotheses. Furthermore, by using these hypotheses, the teacher can generate new tasks to evaluate the student's understanding level. In this way, appropriate instructions based on the student's knowledge structure can be provided.

To accomplish such a behavior within an intelligent tutoring system (ITS), the authors have defined a domain model and applied hypothesis‐based reasoning to diagnose the student model. When the system finds an error in a student's problem‐solving process, it attempts to generate hypotheses which explain that error in terms of the domain model.
A lower bound analysis for bit error rate of trellis‐coded QPSK modulation in impulsive noise environment
Authors: Nakano Etsuhiro , Iwanami Yasunori , Ikeda Tetsuo
Published: July 2007

The efficiency of trellis‐coded modulation (TCM) schemes against Gaussian noise has been well known. However, its performance for impulse noises, which degrade the quality of urban radios, wire communications, and so on, remains unknown.

This paper pays special attention to a trellis‐coded QPSK modulation scheme, for example, and clarifies the analysis method of lower bounds of bit error rates. Also, computer simulations were made to verify the analytical results. As a result, the efficiency of the TCM scheme against the impulse noise has been clarified.
Synthesis of flow networks minimizing the sum of edge capacities
Authors: Kishimoto Wataru , Takeuchi Masashi , Kishi Genya
Published: July 2007

Several methods to construct a flow network minimizing the sum of edge capacities which have the given terminal capacity matrix are already known. However, there exist some networks that cannot be constructed by known methods.

This paper considers the case where the given terminal capacity matrix is an elementary terminal capacity matrix. A method is proposed to construct a flow network with the minimum sum of edge capacities, which has the given matrix as the terminal capacity matrix. Using this method of construction, any flow network with the minimum sum of edge capacities that has the given elementary terminal capacity matrix can be constructed.
Multichannel IIR filter banks composed of all‐pass filters as construction elements
Authors: Wada Shigeo , Takahashi Shin‐Ichi
Published: July 2007

Filter banks are being used in many areas, e.g., voice processing in communication systems; and active research has been on‐going in this field in recent years.

This paper describes a method of realizing multichannel IIR filter banks which could divide the frequency range into an arbitrary number of uniform bands. In this method, filter banks are formed by shifting the low‐pass characteristics with the help of variable transformation with respect to ω and a π/2 phase shifting with the help of a Hilbert transformer. Hence, this design procedure becomes similar to the design of linear‐phase all‐pass filters.

This IIR filter including the Hilbert transformer can be implemented with the help of an all‐pass filter, and thus low coefficient sensitivity property can be realized. Moreover, the transition band is narrower compared to the FIR structure. Other than the forementioned merits, the design is comparatively simple; and all the coefficients can be obtained in an analytical way using Fourier series expansion.
A phase approximation method and stability conditions of all‐pole systems in terms of 2‐D line spectrum pair
Authors: Kato Takayuki , Hamada Nozomu
Published: July 2007

This paper discusses the stability of a two‐dimensional (2‐D) all‐pole system, especially its relation to the phase characteristic. The discussion starts with Ekstrom's stability condition for the asymmetrical half‐plane model, which is the most general as the 2‐D infinite impulse response (IIR) system. The stability theorem known for the phase characteristic of the 1‐D all‐pole system is extended and applied to the 2‐D case. The 2‐D line spectrum pair is introduced as the intersection of the phase characteristic of the 2‐D all‐pole system and a particular set of planes. The stability theorem for the all‐pole system is derived as the condition for such a system. Then, based on the stability theorem for the 2‐D all‐pole system, an approximation method for the phase by the all‐pole system which ensures the stability is proposed.

It is shown that the proposed phase approximation method corresponds to a particular case of the signal restoration using only the phase data given by Oppen‐heim et al. As an improvement of the proposed phase approximation method, the evaluation function by Oppen‐heim based on the error of the equation is replaced by the evaluation function which is the phase error itself. The error minimization method is proposed.

Finally, as an application example, the phase compensation problem by the all‐pass system is considered, and the usefulness of the proposed method is demonstrated.
Numerical analysis of bifurcations in Duffing's equation with hysteretic functions
Authors: Matsuo Tetsuji , Kishima Akira
Published: July 2007

This paper analyzes numerically the bifurcation phenomenon in Duffing's equation containing a hysteretic function and reports on the result of investigation of the effect of the hysteretic characteristics on the bifurcation.

First, a large number of steady hysteresis loops is derived by numerically integrating the state equation of the system with various initial conditions, and the sets of the steady periodic solutions are observed. Then, using the method already proposed by the authors, the bifurcation of the steady solution is analyzed while varying the parameters of the system. The effects of the hysteretic loss and the ohmic loss on the bifurcation of the system are compared, and the difference is discussed. An example of the generation of chaos caused by increasing the hysteretic loss is shown.
Performance of robust detector for very heavy‐tailed noise distribution
Authors: Sato Tatsuo , Yumoto Hideki
Published: July 2007

In previous studies of the robust detector, it is assumed that the noise density function of the nominal function is a “strongly unimodal” density function, with a lighter‐tail than the exponential function. On the other hand, the actually observed noise density function often has a heavier‐tailed density function (more strictly, probability density function) than the exponential function; and the traditional method cannot be applied.

From such a viewpoint, this paper considers the heavier‐tailed density function than the exponential function and introduces the concept of “nonstrongly unimodal” property. The concept is defined; and using the corresponding nominal density function, the robust detector is designed based on the actually observed underwater acoustic data. The performance is examined.

In terms of the performance, the robust detector designed by the authors is compared with the linear and sign detectors. It is shown as a result that the robust detector designed by the authors is much better and useful.
Nonuniform perfect‐reconstruction systems for quadrature mirror filter banks
Authors: Kurosawa Kaoru , Fujita Yoichi
Published: July 2007

By decreasing the decimation ratio to one less than the number of channels, a perfect‐reconstruction quadrature mirror filter (QMF) system can be constructed with the following innovative features: (1) the band division, which in the past has been uniform, can be made nonuniform; (2) the equivalent delay, which has usually been as large as the order of the dividing filter, can now be reduced to a size equal to the decimation ratio minus 1; (3) the number of channels, which has been restricted to a power of 2, can now be arbitrary. In addition, the traditional method employs spectral decomposition, while the proposed method employs Euclidean division. Euclidean structure (the realization of Euclidean division on a network) and lattice structure are considered as methods of constructing a filter that does not produce an aliasing distortion for the finite word length.
Design of a ternary coding scheme and of single‐error‐correcting ternary hamming codes
Authors: Muranaka Noriaki , Imanishi Shigeru
Published: July 2007

The structural units in multivalued (MV) information processing systems, such as the MV arithmetic unit which executes arithmetic operations, the MV memory unit in which MV information is stored, and the MV sequential unit which contains counters, have been widely studied and reported on. There have been very few studies, however, on the encoder and decoder necessary to transmit and store the data in an MV system. In this paper, we present the most primitive ternary codes used in MV error detecting/correcting codes with parallel input signals. Ternary codes are useful for improving the reliability of an MV information processing system.

First, examples of ternary three‐digit codes coded in ternary coded decimal (TCD) are shown and their characteristics described. Then we describe single‐error correcting ternary Hamming code I, code I′, code I″, and code II, from extensions of the binary Hamming codes to ternary. As a result, increases in the maximum code length may be realized. Finally, we present the design of an encoder and decoder with a single‐error correcting Hamming code II in a parallel input system and discuss the implementation of these circuits.
High‐rate, power‐efficient coding for optical communication: Design and performance evaluation
Authors: Uyematsu Tomohiko , Yagi Hideaki , Sakaniwa Kohichi
Published: July 2007

In the direct detection optical communication system which detects the optical pulse by counting the photons, it is known that the information transmitted by each photon has an important role in the performance evaluation of the error‐correcting code, in addition to the code rate and the decoding error rate. Especially, for the code which can achieve arbitrarily small error rate by increasing the code length, the performance of the code can be evaluated based on the code rate and the information efficiency. However, these two evaluation measures are in a trade‐off relation; and there is a limit if one attempts to improve both.

From such a viewpoint, this paper determines the bounds for the code rate and the information efficiency and determines the limit of performance when the ideal error‐correcting code is applied to the direct detection optical communication. Then, as a code which can arbitrarily achieve a small error rate, a new code based on the iterated code is proposed. It is shown that if the code rate is less than 0.75, the proposed code can achieve a better information efficiency than the conventional code with the same code rate.
Effect of stereo television presentation on “mental rotation”
Authors: Nagamine Kazuhito , Nakayama Minoru , Shimizu Yasutaka
Published: July 2007

The effect of stereo television presentation on “mental rotation” was examined. When the orientations of two identical or mirror figures are changed and then displayed, mental rotation is the phenomenon that the time taken to decide this difference is proportional to the angular difference between the orientations of the two figures. First, the reaction times when the presentations were in two and three dimensions were compared, and the effectiveness of the three‐dimensional presentation was studied. The result was that, even when displayed in three dimensions, a mental rotation similar to that of the two‐dimensional case was verified and the reaction time was significantly shortened. The result of studying the internal processes showed that three‐dimensional presentation was effective from the standpoint of the transformation to the internal representation. The subjects were divided into two groups based on their reaction times. When the effectiveness of the three‐dimensional presentation was studied, three‐dimensional presentation was particularly effective for the group with the short reaction times. Furthermore, when a part of the presentation figures were marked with color, the speed for rotating the representation became significantly faster regardless of the presentation dimension. By studying the subjects, we found colored marking was effective for subjects with long reaction times.
Improvement of analysis accuracy of high pitch speech utilizing residual of linear prediction analysis
Authors: Fukabayashi Takeshi
Published: July 2007

This paper proposes a method to improve the accuracy of analysis in the traditional linear prediction analysis by utilizing the information contained in the residual due to the analysis error. In the proposed method, the linear analysis is applied first to the speech data and the residual is determined. At every interval almost equal to one pitch period, “0” sequences composed of more than one “0” are inserted into appropriate positions of the residual and the sequence is prolonged to the backward direction. The linear prediction analysis is applied to the resulting sequence.

When the residual of the sequence with more inserted “0′s” than the order of the residual analysis is processed, the autocorrelation coefficient up to the delay needed for the analysis is equal to the sum of the independently determined autocorrelation coefficients between “0” sequences. Consequently, the result is almost equal to the analysis of the residual for almost one pitch period using the average autocorrelation function. This reduces the effect of the pitch period of the residual.

Next, the impulse response sequence of the all‐pole filter constructed from the linear prediction coefficients of the residual is determined. The spectrum of the forementioned impulse response sequence is an approximation of the spectral envelope of the residual. The foregoing impulse response sequence is passed through the all‐pole filter determined previously from the linear prediction coefficients of the speech. The output, i.e., the synthesized waveform, is analyzed. It is shown by the analysis experiment of the synthesized speech that the accuracy of the analysis can be improved by this method.
Generalized representation of integers
Authors: Chujoh Takeshi , Hirasawa Shigeichi , Inazumi Hiroshige , Nishijima Toshihisa
Published: July 2007

By the problem, called a representation of the integers, is meant the encoding of the positive integers without a known upper bound, for which unique decoding can be provided. From the viewpoint of information theory, this problem has been discussed theoretically in its relation to the universality, asymptotic optimality, and computation theory. The result in those approaches has been applied to the data compression scheme for the type of data referring to the past as well as the URR and other floating‐pointnumber representations with variable exponential length.

This paper discusses representation of the integers problem from the viewpoint of the codeword‐length function, which is the function to represent the length of the codeword. As a result, a general construction method is presented which has the desirable property and can uniquely encode all representations.

Several methods are given from this approach, which can construct not only the traditional representations of the integers but also the first representations of the integers which has not been considered. It is noted first that two construction methods of codeword length, which are independent of the encoding, are considered. One is based on the combination of the codeword‐length functions, and the other is based on the codeword‐length distribution. More precisely, it is shown that not only are the traditional representations derived, but also the representations that have not been considered in the past. Using detailed examples, it is shown that the computational complexity of the encoding and decoding depends on the codeword‐length function.
FITS: A generic framework for intelligent tutoring systems
Authors: Ikeda Mitsuru , Mizoguchi Riichiro
Published: July 2007

This paper summarizes the research result up to the present concerning the generic framework FITS for ITS. FITS is composed of six building blocks, which are teaching‐material‐independent, and the scheduler to realize the flexible teaching process. By developing the generic framework reflecting the essential task structure of ITS, the manpower needed in developing ITS can be reduced.

This paper describes the design philosophy of the generic framework FITS and the mechanisms of the building blocks using the case of the teaching of geography as an example.
Generation of review task sequences based on teaching‐material structures and learning progress
Authors: Yonezawa Nobuyoshi
Published: July 2007

When two‐dimensionally structured teaching materials are rearranged into a one‐dimensional sequence according to the teaching strategy, it is called teaching task sequence. The teaching is executed by presenting the tasks in the order in this sequence.

This paper considers the situation where a task arises in the teaching task sequence whereby the learner cannot understand and proposes an algorithm to generate the review task sequence so that the learner can understand the task as fast as possible. The review task sequence is derived from learning progress and the structure of the teaching material.

The directional connection called influential strength is introduced between the nodes in the teaching material structure graph, and the structure of the teaching material composed of N nodes is described by a square influence matrix of N‐th order with the influential strength as the element. The review task sequence is a real‐valued sort, which is obtained by operating the teaching record matrix to the influence matrix representing the tree structure, not by tracing the directed edges of the graph.
Algorithm–oriented information‐processing education
Authors: Kusunoki Fusako , Miyauchi Arata , Ozawa Shinji
Published: July 2007

Recently, information‐processing education has increasingly been called upon to teach problem analysis and solution skills. However, due to the burden of having to learn many programming language rules, beginners cannot adequately acquire these skills in conventional information‐processing education.

This paper proposes algorithm‐oriented information‐processing education. First, to teach good algorithm style, algorithm teaching is separated from programming language instruction. To enable beginning students to study algorithms without knowing a programming language, the program analysis diagram (PAD) compiler and the PAD simulator are prepared as educational tools.

It is believed that in this algorithm‐oriented curriculum students can learn problem analysis and solution skills and, as a result, will be able to write highly maintainable computer programs. A curriculum based on the suggestions from the authors' research was implemented for two years and yielded favorable results which are reported here.
Small love‐wave SAW resonators with very low capacitance ratio
Authors: Shimizu Hiroshi , Suzuki Yuji
Published: July 2007

When a strip grating of periodic strips of Au, Ag, or Pt is produced on a rotated Y‐cut LiNbO3, a Love‐type surface wave with a high coupling (K2 > 30 percent) is formed and the reflection coefficient per strip is as large as several tens percent.

In this paper, a small IDT resonator, with an extremely low capacitance ratio making use of the Love‐type surface wave, is studied theoretically and experimentally.

First, the admittance characteristics of the IDT are studied by means of the mode‐coupling equation, which is determined by the dispersion characteristics derived from the Floquet theorem. It can be shown that the IDT exhibits resonant characteristics and the capacitance ratio is 2.4 – 2.7 if the number of pairs is more than 10.

Next, an experiment was carried out by using a combination of the Y‐X LiNbO3 substrate and the Au electrodes. It is demonstrated that the resonator with a low‐capacitance ratio can be realized, as predicted by the theory. Further, rhombically weighted electrodes are proposed. It is confirmed that the spurious transverse mode and the spurious longitudinal mode can be suppressed simultaneously.
Synthesis of low‐sensitivity second‐order real digital filters using complex two‐port adapters
Authors: Murakoshi Nobuo , Nishihara Akinori , Watanabe Eiji
Published: July 2007

If complex coefficients are used in the realization of the real‐coefficient transfer function, the degree of freedom in the circuit construction is enhanced. This creates a possibility that a lower‐sensitivity filter can be realized than in the traditional low‐sensitivity filter using the real coefficients.

This paper discusses a method to construct the second‐order real‐coefficient IIR filter using the complex two‐port adapter. First, by using the complex two‐port adapter, a method for circuit construction is proposed where the second‐order bandpass, lowpass, high‐pass, and asymmetrical bandstop transfer functions are realized.

The proposed circuit can be realized with fewer number of multipliers than the conventional circuits using complex coefficients. Then a method is shown which selects the complex two‐port adapter according to the value of the real part of the coefficient of the complex multiplier.

By this selection method, the circuit with the lowest sensitivity in regard to the real part can be realized without increasing the computational complexity for the circuit. Furthermore, a method is considered to reduce the sensitivity also for the imaginary part of the complex multiplier coefficient. Finally, using a simple example, it is verified that the circuit obtained by the proposed construction method has the low sensitivity.
Bifurcation set in a nonlinear compound system
Authors: Hirai Kazumasa , Adachi Tomohiko
Published: July 2007

A bifurcation phenomenon may occur in a nonlinear system where the number of equilibrium points or their properties change by a small change of parameter. The set of parameters that can produce the bifurcation phenomenon is called the bifurcation set.

In general, it is difficult to determine the bifurcation set when the order of the system is increased. However, when the linear part of the system can be transformed into the controllable canonical form, the determination of the bifurcation set for the higher‐order system can be reduced to that of the one‐dimensional system.

This paper derives the method to determine the bifurcation set for the compound discrete‐time system based on that idea. First, a certain class of compound system composed of a series connection is considered and the kind of bifurcations that can be generated is analyzed. Then it is shown that the number of variables needed to determine the bifurcation set can be reduced to the number of decomposable subsystems in the case of a generally connected system.
Design of IIR digital filters with given magnitude specifications using allpass networks
Authors: Zhang Xi , Iwakura Hiroshi
Published: July 2007

This paper proposes a direct design method in the z‐domain for the IIR digital filter with a parallel structure composed of allpass networks with complex and real coefficients, with the specifications for the bandedge frequencies of the passband and stopband as well as the magnitude in the passband (or stopband).

First, a filter composed of two allpass networks with conjugate complex coefficients is considered. Also, the phase difference characteristic between the two networks is considered. By specifying the phase difference error, the determination of the filter coefficients is reduced to the eigenvalue problem of the matrix using Remez' algorithm. The filter coefficients are determined from the eigenvector corresponding to the maximum eigenvalue. Then iterative calculation is executed to realize the equiripple characteristic, and the optimal solution is derived.

Next, the relation between the phase difference errors and the magnitude errors is discussed and it is shown that the filter can be designed by the proposed method by specifying the absolute value of the magnitude error. The usefulness of the proposed method is shown by design examples. The filter based on two allpass networks with real coefficients is also considered, and it is shown that the filter can be designed by the same procedure by formulating the procedure for the sum and the difference of the filter coefficients.
Concatenated coding scheme with variable coding gain
Authors: Kojima Toshiharu , Fujimura Akinori , Miyake Makoto , Fujino Tadashi , Yoshida Hideo , Yamagishi Atsuhiro
Published: July 2007

The concatenated coding scheme using convolutional coding with Viterbi decoding for inner code and Reed‐Solomon (RS) code for outer codes is an attractive scheme that can achieve a coding gain larger than that of the convolutional coding with the Viterbi decoding scheme. Hence, it has attracted attention in a wide range of fields in satellite communications from space communications to digital image transmission systems.

This paper presents the configuration and characteristics of a newly developed concatenated coding scheme with variable coding gain. This scheme enables selection of a coding gain considering the signal processing time of coding and decoding by enabling selection of: 1) the block length of the RS code (and its error‐correction capability); 2) the depth of interleaving combining the inner and outer code by a single codec. In addition, in this scheme, a new synchronization word detection method was developed and employed. In this method, nonlinear conversion is applied to soft decision demodulated data to synchronize the RS codeword and interleaving. It has been confirmed by numerical calculations that this synchronization word detection method has characteristics further improved over those of the conventional soft decision synchronization word detection method which is superior to the hard decision method. An experimental system was developed and the field test via Ka‐band satellite of communication satellite No. 3 (CS‐3) was performed, and the tradeoff relationships between the coding/decoding signal processing time and coding gain have been clarified quantitatively.
Bit error rate analysis of multilevel coding scheme and optimum error‐correcting capability assignment for impulsive noise
Authors: Kaneda Kazuyuki , Ogiwara Haruo
Published: July 2007

The advantage of the multilevel coding scheme is that the coding can be performed independently for each level, and the optimal coding can easily be determined for the channel with superposed noise with arbitrary probability density distribution. To evaluate the performance of this coding scheme, an approximate formula for the bit error rate after decoding is derived. As an example, the channel with the impulsive noise is considered. Using the approximate formula, the error‐correcting capability is assigned optimally to the levels and the coding gain of 20 dB is obtained for the BCH code of code length 31. The foregoing result is confirmed by a computer simulation. A report has already been proposed for the case where the errors of the decoder outputs are randomized except for the top level, by interleaving among the levels. However, a problem arises in that the delay as well as the circuit scale is increased. From such a viewpoint, this paper discusses the case without inter‐leaving. Finally, the performances are compared between the cases with and without interleaving among levels.
Optimal diagonal approximation of the covariance function with respect to the relative entropy using the wavelet basis
Authors: Sakaguchi Fuminori
Published: July 2007

If the covariance function of a random signal can be written in a diagonal form via the wavelet basis, this random signal can be regarded as a superposition of the wavelets which arise randomly. However, it is known that, in general, such an expression is not possible.

In this paper, in place of a perfect diagonalization, an optimal approximate diagonalization in the sense of the relative entropy is investigated theoretically. Especially, it is shown that when a set of wavelets forming complete orthonormal sets (expressed in a vector form as {ϕi} is used as the basis, an optimal diagonal approximation of the covariance matrix Γ is not the diagonal form\documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_k {\left({\bar \phi _k ^T \Gamma \phi _k} \right)} \phi _k \bar \phi _k ^T $\end{document}using the so‐called “wavelet spectrum” but\documentclass{article}\pagestyle{empty}\begin{document}$ \sum\limits_k {\left({\bar \phi _k ^T \Gamma ^{- 1} \phi _k} \right)^{- 1}} \phi _k \bar \phi _k ^T $\end{document}Further, several examples are given where Haar wavelets are used.
Immunopathology in schistosomiasis is controlled by antigen‐specific regulatory T cells primed in the presence of TLR2
Authors: Layland Laura E. , Rad Roland , Wagner Hermann , da Costa Clarissa U. Prazeres
Published: July 2007

Regulatory T cells (Treg) are vital in maintaining the homeostasis of immune reactions. In chronic infections, such as schistosomiasis, it remains unclear whether engagement of the TLR family is required to induce Treg activity. Thus, we performed in vivo studies using TLR2–/– mice infected with Schistosoma mansoni and found elevated immunopathology, decreased egg burden and extended antigen‐specific Th1 responses. Simultaneously, the population of Treg failed to expand. To evaluate the role of Treg during infection, we functionally inactivated CD4+CD25+ T cells and observed that the resulting immunopathology mirrored that in TLR2–/– mice. Egg burden was also reduced in anti‐CD25‐treated mice, indicating that without Treg eggs are more efficiently destroyed. In addition, antigen‐specific T cells from both TLR2–/– and anti‐CD25‐treated mice displayed an extended Th1 phase. Finally, adoptive transfer of schistosome‐primed, but not naive CD4+CD25+ T cells was able to resolve the immunopathology in TLR2–/– recipients and interestingly, this amelioration was independent of TLR2 being present on the transferred Treg. We conclude that TLR2 is necessary for priming active Treg and their expansion during schistosomiasis.
Thermodynamics of Complexes between Dibenzo‐24‐crown‐8 Derivatives and 1,2‐Bis(pyridinium)ethanes
Authors: Liu Yu , Li Chun‐Ju , Zhang Heng‐Yi , Wang Li‐Hua , Li Xiao‐Yun
Published: July 2007

The binding behavior of para‐substituted 1,2‐bis(pyridinium)ethane derivatives (X‐PyCH2–CH2Py‐X, X = H, Me, Ph, and Py) a–d with dibenzo‐24‐crown‐8 (DB24C8, 1) and its derivatives, diformyldibenzo‐24‐crown‐8 (2), dinitrodibenzo‐24‐crown‐8 (3), dimethyldibenzo‐24‐crown‐8 (4) and diaminodibenzo‐24‐crown‐8 (5), has been comprehensively investigated by 1H NMR and UV absorption spectroscopy and isothermal titration microcalorimetry in acetonitrile. The results obtained indicated that some of the complexes constructed from DB24C8 derivatives and 1,2‐bis(pyridinium)ethane derivatives resulted in visible color changes. For example, upon the addition of equimolar proportions of 5, the colorless CH3CN solution of d changed to red. Furthermore, we investigated the thermodynamics of the complexation of crown ethers 1–5 with guests a–d, and found that the nature of the substituents attached to 1,2‐bis(pyridinium)ethanes and the catechol rings on DB24C8 dramatically affects the molecular recognition behavior and the binding thermodynamics. Thermodynamically, the formation of these complexes is an enthalpy‐driven process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Copper‐Catalyzed Synthesis of 2,3‐Disubstituted Indoles
Authors: Tanimori Shinji , Ura Haruna , Kirihata Mitsunori
Published: July 2007

The copper‐catalyzed one‐step synthesis of 2,3‐disubstituted indoles from readily available starting materials, 2‐iodoaniline and various β‐keto esters was described. The advantage of this method is the use of cheap catalysts and simple experimental procedures under mild reaction conditions. As the substituted indole derivatives are important starting materials for the synthesis of biologically active indole alkaloids and drug candidates, this method would have potential usage for above purpose.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Patterns of decline and evidence of subgroups in patients with Alzheimer's disease taking galantamine for up to 48 months
Authors: Rockwood Kenneth , Dai Dingwei , Mitnitski Arnold
Published: July 2007

Background

Lacking long‐term placebo‐controlled trials of cholinesterase inhibitors (ChEIs) in Alzheimer's disease, how decline is modeled is crucial to interpreting the effects of long‐term, open‐label use. We aimed to: 1) understand changes in cognition and function in people taking galantamine; (2) identify treatment subgroups.

Methods

This is an open‐label long‐term extension (up to 48 months) of two placebo‐controlled clinical trials from Europe and Canada. At baseline, 240 patients with mild‐moderate Alzheimer's disease at baseline had received galantamine continuously for 36 months. The trajectory of scores on the Alzheimer's Disease Assessment Scale—Cognitive Subscale (ADAS‐Cog) and the Disability Assessment for Dementia (DAD) was modeled over 48 months. Goodness of fit was compared using normalized residuals and by calculating correlation coefficients between observed and fitted data. Iterative K‐means clustering identified subgroups.

Results

Of 240 patients, 51 (21%) withdrew between months 36–48 (nine died and 12 with adverse events). The mean ADAS‐Cog worsened from 22.6 (mean) ± 8.6 (SD) at baseline to 31.3 ± 3.1, with similar changes in the DAD. The logistic function fit better (ADAS‐Cog norm of residuals = 2.05, r = 0.993; DAD = 2.21, r = 0.998) than the commonly used Stern equation (ADAS‐Cog = 4.22, r = 0.944; DAD = 7.51, r = 0.986). K‐means clustering identified three stable groups; least decline (n = 82), persistent progression (n = 75), and an intermediate group (n = 82). Initial conditions were important: the mean ADAS‐Cog score for those with least decline was 15 ± 8, better than both the intermediate group (20 ± 9) and persistent progressors (30 ± 10; p < 0.001).

Conclusions

Alzheimer's disease patients show variable long‐term decline that is best modeled as a logistic function, not as linear decline. Over 48 months, about one‐third of patients showed little decline, while one‐third showed important decline. Copyright © 2007 John Wiley & Sons, Ltd.
Does physical activity moderate the association between depressive symptoms and disability in older adults?
Authors: Lee Yunhwan , Park Kyunghye
Published: July 2007

Objective

Depressive symptoms and disability are closely associated and known to have reciprocal relationships. This study examines whether physical activity moderates the association between depressive symptoms and disability in community‐dwelling older adults.

Methods

Baseline and 1‐year follow‐up data of 645 persons aged 65 years or older from the Suwon Longitudinal Aging Study were analyzed. A 15‐item Geriatric Depression Scale, Physical Functioning scale, and physical performance tests were used to assess the individual's depressive symptoms and functional disability. Physical activity was defined as the recommended level of exercise based on its frequency and intensity. Multiple regression analysis with generalized estimating equations was conducted to examine the physical activity's role as an effect modifier in the association between depressive symptoms and disability.

Results

Physical activity was a significant effect modifier in the ‘depressive symptoms–disability’ association, controlling for sociodemographic characteristics and health‐related covariates. Moderate‐intensity activity was as effective as vigorous activity in moderating the relationship. The moderating effect was notable among those displaying severe depressive symptoms and functional disability. Over time the strength of the association between depressive symptoms and disability tended to diminish for those engaging in physical activity.

Conclusion

The association between depressive symptoms and disability is moderated by physical activity in older persons. The findings suggest that healthcare professionals need to promote moderate amount of physical activity as a potential intervention tool in attenuating the depression–disability connection in later life, especially among those with high levels of physical and mental impairments. Copyright © 2007 John Wiley & Sons, Ltd.
Vascular disease and apathy in old age. The Leiden 85‐plus Study
Authors: van der Mast R. C. , Vinkers D. J. , Stek M. L. , Bek M. C. , Westendorp R. G. J. , Gussekloo J. , de Craen A. J. M.
Published: July 2007

Background

Apathy is defined as an important loss of motivation in all domains of daily functioning. Especially in old age, apathy might be a specific neuropsychiatric syndrome separate from depression. There are indications that apathy in elderly subjects is related to vascular disease.

Objective

To assess the relation between vascular disease and apathy in subjects aged 85 years and older.

Methods

The Leiden 85‐plus Study is a prospective, population‐based study of 500 elderly subjects. Vascular disease including myocardial infarction, angina pectoris or myocardial ischemia, claudicatio intermittens, and arterial surgery was determined at baseline. Symptoms of apathy were assessed annually from age 85 through 90 years using the apathy questions of the 15‐item Geriatric Depression Rating Scale (GDS). Diagnostic accuracy of the apathy questions was validated using the Apathy Scale at age 90 years. The association between vascular disease and apathy was estimated both at baseline and longitudinally.

Results

The apathy items of the GDS showed a sensitivity of 69% and a specificity of 85%. At baseline, 69 subjects with apathy but free of depression had significantly more cardiovascular pathologies compared to 287 subjects without apathy. In the 287 subjects who were free of apathy and depression, increase of apathy but not depression during follow‐up was significantly higher for each additional cardiovascular pathology at baseline.

Conclusion

In community dwelling elderly, those with vascular disease were at higher risk of developing apathy but not depression. This suggests that apathy and depression in old age have different etiologies. Copyright © 2007 John Wiley & Sons, Ltd.
Screening for elder abuse in dementia in the LASER‐AD study: prevalence, correlates and validation of instruments
Authors: Cooper Claudia , Manela Monica , Katona Cornelius , Livingston Gill
Published: July 2007

Background

Several studies have investigated abusive behaviour by carers towards people with dementia, most using unvalidated scales; only two reported correlates of abuse after controlling for mediators and confounders, and these controlled for different factors.

Objective

To investigate the acceptability and validity of the Modified Conflict Tactics Scale (MCTS) and abuse correlates.

Methods

Eighty‐six people with Alzheimer's disease and their family carers, originally recruited for a representative community study were interviewed. We asked carers about acceptability of the MCTS and investigated its validity by comparing scores to the Minimum Data Set (MDS) abuse screen (an objective measure) and testing hypotheses that MCTS score would correlate with the COPE dysfunctional coping scale but not carer education.

Results

Twenty‐four (27.9%) were identified as abuse cases by interview. No care recipients (CRs) screened positive for abuse using the MDS screen. Seventy‐two (83.7%) participants thought that the scale was acceptable, ten (11.6%) that it was neither acceptable nor unacceptable, and three (3.5%) that it was unacceptable. As hypothesised, MCTS scores correlated with dysfunctional coping scale score but not carer education.

Conclusions

This is the most comprehensive study so far in this field. The MCTS was acceptable and had convergent and discriminant validity for measuring carer abuse. The MDS failed to identify cases of abuse. Carer male gender and burden, and greater CR irritability, cognitive impairment but less functional impairment predicted carer abusive behaviour. Our findings appear to refute UK government elder abuse reduction policy which assumes that few incidents of abuse arise from carer stress. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis of an acyclic diselenodithioether ligand tethered with bulky substituents and its application to the synthesis of a distorted octahedral palladium(II) complex
Authors: Takeda Nobuhiro , Isobe Toru , Tokitoh Norihiro
Published: July 2007

A newo‐phenylene‐bridged diseleno‐dithioether ligand tethered with an extremely bulky substituent, 2,4,6‐tris[bis(trimethylsilyl)‐methyl]phenyl (Tbt) group, at both terminal selenium atoms, [TbtSe(o‐phenylene)S]2(o‐phenylene) (3), was synthesized by taking advantage of the reaction of TbtSeSeTbt (4) with 1,2‐diiodobenzene using Cu2O in 2,4,6‐trimethylpyridine followed by the successive coupling reaction of the resulting bulkyo‐iodophenylselenide (5) with 1,2‐benzenedithiol. Complexation of3with Na2PdCl4gave the corresponding dichloropalladium(II) complex, [PdCl2(3)] (6). The X‐ray structural analysis of6indicated that the central palladium metal is in a distorted octahedral environment, where the two inner sulfur atoms of3and the two chlorine atoms form a square planar arrangement around the palladium metal and the two terminal selenium atoms of3weakly coordinate to the palladium center at the axial positions. The AIM calculations also indicated the existence of the interaction between palladium and selenium atoms in the crystalline state. On the other hand, the77Se NMR spectrum suggests that there are no or very weak interactions between the palladium and selenium atoms of3in solution. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:549–556, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20339
Stereocontrolled reactions mediated by remote sulfoxides: Formation and reactivity of enantiomerically pure benzylic centers
Authors: García Ruano José Luis , Martín Castro Ana M.
Published: July 2007

Reactions of different electrophiles (alkyl halides, aldehydes, N‐sulfinylimines, imines, etc) with (S)‐2‐p‐toluenesulfinyl toluene and their alkyl, triisopropylsilyloxy, and methylthio derivatives at benzylic position, in the presence of LDA, allow the synthesis of a variety of enantiomerically pure benzylic centers, whose configuration is efficiently controlled by the γ‐sulfinyl group, according to 1,4‐asymmetric induction processes. With prochiral electrophiles, the 1,5‐asymmetric induction processes can also be controlled either by modifying their steric or electronic features or by incorporating an additional chiral center at the electrophiles. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:537–548, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20342