bluuebunny/crossref_metadata_2025 huggingface dataset:
Matching section with a nonuniform transmission line having equivalent representation constructed with lumped brune‐type section and uniform transmission line
Authors: Ohba Yoshifumi , Sato Risaburo , Nemoto Yoshiaki
Published: July 2007

The nonuniform transmission line (NTL‐SR), which is equivalently represented by a lumped series‐resonant circuit, a uniform transmission line and a lumped T‐type Brune section with a negative sign, has the property of extreme points in the characteristic impedance distribution. By utilizing those extreme points positively, an excellent matching section can be produced for the pure‐resistance load using NTL‐SR.

This paper first derives the equivalent circuit for the NTL‐SR fitted to matching section (NTL‐SRMS). The NTL‐SRMS is the NTL‐SR where the characteristic impedance distribution has zero derivatives at the input and the output ends. Then the transmission characteristics of NTL‐SR as the matching section are shown. Based on those results, the design of this type of matching section is discussed. Finally, the result of an experiment is reported to demonstrate the validity of the theory.
Dc analysis of nonlinear circuits using solution‐tracing circuits
Authors: Inoue Yasuaki
Published: July 2007

The dc driving‐point and transfer characteristics of nonlinear circuits are the multivalued curves that arise from the nature of the circuit. These curves cannot be analyzed by general‐purpose circuit simulators. One known method for analyzing these kinds of characteristic curves is the backward differentiation formula (BDF) curve‐tracing algorithm proposed by Ushida and Chua. In this method, the circuit equations f(x) = 0, f(·): Rn+1 → Rn, where the input voltage is assumed to be a variable, are analyzed by the predictor‐corrector algorithm where the arc‐length of the solution curve in n + 1‐dimensional space is the parameter. However, it is not clear that this method is practical for large‐scale circuits.

In this paper, we extend the Ushida‐Chua method from a practical method standpoint and demonstrate that the multivalued characteristic curves of large‐scale circuits can easily be analyzed using general‐purpose circuit simulators.

In the proposed method, first, the solution curve in n + 1‐dimensional space is projected into m + 1‐dimensional space, where m ≤ n and the arc‐length of this new curve is used as the parameter.

Second, the relationship between the arc‐length and the components of the curve is expressed by a function generator circuit, the solution‐tracing circuit.

Finally, transient analysis is performed using a general‐purpose circuit simulator and the solution curve is traced. The effectiveness of this method is verified through several examples, including a bipolar analog IC with 296 nodes.
Development of functional simulation model of CMOS memory
Authors: Hayashi Shin‐Ichi , Watanabe Toshinori , Hirai Chiaki , Masuda Hiroo
Published: July 2007

The development of semiconductor integration has brought with it the system‐on‐chip era. The small‐quantity productions of diversified kinds of IC are required at the stage of ASIC (application specific IC). Thus, it has become important to reduce the design period for the mixed analog/digital circuit. The capacity of the CMOS memory continues increasing and is expected to expand from the Mbit level to the Gbit level. Then the parasitic effect will be a problem.

This paper proposes a functional simulator based on the continuous system simulation technique. It is shown that the proposed simulation including the parasitic effect can effectively be applied to the functional design of CMOS memory, which has been unsatisfactory in the early circuit simulator.

In the proposed method, CMOS memory is modeled based on the functional element model of the CMOS memory and the functional simulation can easily be realized considering the parasitic functional effect. This helps to improve the design quality and to reduce the design period.
A study of generating functions of sampling theorems and optimum interpolation functions minimizing some kinds of measures
Authors: Kida Takuro , Sa‐Nguankotchakorn Somsak
Published: July 2007

Given an absolutely square‐integrable waveform bandpass limited to the interval |ω| ≤ ω0, ω0 > 0, and regularly spaced sample points tn = nτ0, (τ0 = π/ω1 > ω0; n = 0, ±1, ±2, …) the interpolation formula which corrects errors in the sample values of the original waveform is not uniquely determined. In this paper, we derive several theorems which establish the relation between the interpolation functions and a two‐variable function of angular frequency ω and time t called the generating function of the sampling theorem. First, we show that these interpolation functions may be considered as functions of time with coefficients obtained from the Fourier series expansion of the generating functions with respect to the angular frequency ω. This theorem depends on another already established theorem, for which a brief proof is given in the Appendix, for the reader's convenience, in the case that the relation is defined on a vector space. Next, under the condition that the generating function is absolutely continuous, we consider the problem of determining a generating function that minimizes the sum of the squares of the weighted interpolation functions. We show that the sum of the squares of the weighted interpolation functions as a measure provides a bound on the magnitude of the interpolation functions and also measures the rate of decrease. In this paper, under two conditions, which are satisfied in the sampling theorem, a generating function in the sampling theorem is determined which minimizes the above‐mentioned measure of the interpolation functions. Using these arguments, we also derive generating functions which minimize various weighting measures related to the interpolation functions ωn(t), such as when the weights are squares, (2k)‐th powers, and (1 + n2ω).
Existence of structurally bounded wave digital filters for arbitrary transfer functions
Authors: Ishiwata Shunichi , Nishihara Akinori , Fujii Nobuo
Published: July 2007

Structurally bounded circuits such as properly designed wave digital filters (WDFs) are known to have low sensitivity in the passband. Existing structurally bounded WDFs cannot always realize arbitrary transfer functions.

This paper shows first the existence of structurally bounded WDF sections which correspond to reactance E sections and Richards sections and then derives their circuit structures. Such a natural assumption is made in this derivation that multiplier coefficients having the same nominal value continue to have the same value even under finite wordlength condition. Interconnections of the proposed sections cause delay‐free loops, which can be removed using Kuroda's identity. Thus, it is shown that such WDFs that can realize arbitrary transfer functions while inheriting the structural boundedness of prototype reactance filters really exist.
Formalization of teaching materials for a network‐based laboratory support system
Authors: Sugawara Kenji , Ukigai Masahiro , Fukushima Manabu , Miida Yoshiro , Kinoshita Tetsuo
Published: July 2007

As the information in society becomes more complex, the importance of advanced education and lifelong learning in universities and corporations is increasing. Since the current situation in general education at universities, for example, is group instruction of a large number of students, instruction that responds to the differences in ability of each student is becoming difficult.

To improve this situation, the trend of the falling price of computers in recent years has been accompanied by energetic research on laboratory support systems. Although when considering the presentation of a superior user interface, the development support and management of the vast amount of teaching materials that accompanies the diversification of the learning objectives, and the implementation of ample teaching support functions, earlier computer‐based systems seem to have functional limits.

Therefore, the transition to network‐based laboratory support systems that use advanced workstations is demanded. However, in building this type of laboratory support system, the formalization of the teaching materials suited for use in a distributed environment is required, but this kind of research has not been performed in the past.

This paper introduces a new framework for formalizing the structure of teaching materials to be used in distributed environments. In addition, its efficiency is discussed as the model used for teaching materials in the implementation of a network‐based laboratory support system, which is being designed and developed.
Realization of two‐dimensional digital filters with powers‐of‐two coefficients
Authors: Todaka Chiaki , Kambayashi Noriyoshi
Published: July 2007

This paper aims at the simplification of operation and the reduction of hardware complexity and presents the construction of the two‐dimensional digital filter using powers‐of‐two coefficients. The proposed two‐dimensional digital filter is composed of a cascade connection of one‐dimensional digital filters with different frequency axis. The digital filter is structured as a cascade connection of the stopband‐forming filter and the passband‐compensating filter.

The stopband‐forming filter is composed of the cascade connection of recursive running sum (RRS), and the passband‐compensating filter is constructed as a linear‐phase FIR or IIR type. The proposed method is especially effective for constructing a narrowband LPF. The zero coefficient sensitivity is realized by eliminating the multiplier. Another point is that the elliptic or polygonal two‐ dimensional filter can be approximated, which has been impossible by McClellan transform.

The proposed method can realize more general two‐dimensional digital filters with a smaller hardware complexity, thereby eliminating the multiplier. Finally, it is verified by design examples that the hardware complexity is reduced in the proposed two‐dimensional digital filter, compared to the traditional method.
Sampling and reconstruction of smooth three‐dimensional convex shapes
Authors: Ohtake Kohhei , Kaneko Michio
Published: July 2007

In digitally transmitting or recording three‐dimensional shapes, to decrease the amount of transmitted information and memory volume, investigations of efficient shape description and sampling‐reconstruction methods are considered important.

This paper investigates these problems with shapes restricted to smooth, bounded three‐dimensional convex shapes.

First, as the representation methods of these shapes, the tangential plane polar coordinate representation is shown and it is explained that this is an efficient representation consistent with the curvature.

Next, from this representation function, spectra and band of the shape are introduced by using surface harmonics as basic functions and their fundamental properties are described. Based on this, a sampling theorem of three‐dimensional shapes is shown which states that for band‐limited shapes, the shape can be reconstructed from a fixed number of sample values. Moreover, for band‐unlimited shapes, distortion occurs in shapes reconstructed from a finite number of sample values.

A sampling method is shown which minimizes this shape distortion power and clarifies that the method is a variable density sampling which arranges sampling points with density proportional to the curvature of shape.

Finally, simulation results of shape‐sampling and reconstruction system performed on ellipsoid to confirm the authors' theory are described.
Development of support facilities for arithmetical word problem exercises in intelligent tutoring system
Authors: Hirashima Tsukasa , Kohno Takahiro , Kashihara Akihiro , Toyoda Jun'Ichi
Published: July 2007

In the problem solving of the arithmetical word problems, the process until the solution method is identified as the most important.

It is necessary to design and develop the basic functions for exercise problem support in an intelligent tutoring system (ITS), such as problem solving, problem generation, and problem explanation, aiming at the support for the identification of the solution method. In this study, those three basic functions are realized based on the problem‐solving method MIPS (model of indexing in problem solving).

This paper describes the problem‐solving module, the problem‐generation module and the problem‐explanation module. The problem‐solving module not only solves the arithmetical word problem but also generates the cognitive description of the identification process for the solution method. The problem‐generation module can generate the problem which specifies what students should do in the identification process. The problem explanation module can indicate the equivalence and difference between any two problems concerning the identification process.
Minimization of coefficient sensitivity for block‐state realizations of state‐space digital filters
Authors: Tsunekawa Yoshitaka , Shida Junichi , Kawamata Masayuki , Higuchi Tatsuo
Published: July 2007

This paper considers the case where the block‐state realization is applied to state‐space digital filters and discusses the synthesis method for the minimum coefficient sensitivity realization.

First, the method to evaluate the coefficient sensitivity in the block‐state realization, which has already been reported by the authors, is shown. Then the synthesis method for the minimum coefficient sensitivity realization is presented based on the evaluation method for the cases with and without the scaling constraint. It is shown as a result that the minimum coefficient sensitivity realization can be derived as a balanced structure also in the block‐state realization, as in the usual state‐space realization.

Finally, calculation examples are shown for those synthesis methods and the validity of the proposed synthesis method is demonstrated by the satisfactory results. It is shown also that the minimum coefficient sensitivity structure for the block‐state realization derived by the proposed synthesis method is equivalent to the filter structure in the block‐state realization, which is derived from the minimum coefficient sensitivity structure in the usual state‐space realization.
A new method of pitch modification by complex cepstrum analysis‐synthesis
Authors: Seiyama Nobumasa , Takagi Tohru , Umeda Tetsuo , Miyasaka Eiichi
Published: July 2007

This paper proposes a new method of high‐quality pitch modification by complex cepstrum analysis‐synthesis algorithm (hereafter referred to as the CCAS algorithm).

The algorithm of the new conversion method presented here is as follows: the complex cepstra obtained within each pitch‐synchronized frame are divided into pitch components and other spectral components by using comb filters.

The pitch pulses obtained by inverse transformation of the pitch components are equalized adaptively to zerophase, while the spectral components also are transformed inversely into unit responses in time‐domain. This equalization makes the pitch components more impulsive, resulting in clear separation of the voice source from the vocal tract characteristics. Speech synthesis is performed by convoluting the phase‐adjusted pitch pulses with the nit responses.

The results of listening tests showed that the pitchmodified speech by the CCAS method subjectively retains as high quality as the original speech.
Relations between the constants of electrostrictive materials and some examples of their application to piezoelectric ceramics
Authors: Cho Yasuo , Matsuno Fumihiko
Published: July 2007

This paper describes the piezoelectric phenomenon caused by the electrostrictive effect from the standpoint of material constants. First, the e, d, g, and h types of basic equations for the piezoelectric phenomenon including the nonlinear terms will be discussed to clarify the transformation formula between nonlinear constants.

The forementioned formula is essential in the analysis of the material constants. Then the relationships among the constants before and after the polarization operation including the nonlinear constants will be clarified.

It will be shown that if the deformation by polarization is small, the material with C∞ symmetry which is obtained by the polarizing isotropic body has a fewer number of independent constants than a 6‐mm crystal.

Finally, the foregoing results will be applied to PZT ceramics and it will be shown that the theory of electrostriction is useful in evaluating piezoelectric ceramics.
Conversion of sinusoidal frequencies to gray code
Authors: Noro Yuichi , Inomoto Kenji , Kuno Kazuhiro
Published: July 2007

A method of straightforward conversion of sinusoidal frequency to Gray code expression is described. The unknown frequency is estimated using only the sign of the inverse cosine function. The frequency conversion error is shown by computer experiment. For a more accurate result, the majority decision principle and threshold logic, that is, a maximum likelihood estimator, are applied. Hardware implementation is so easy that the whole system can be implemented on an LSI chip.
Robust stabilization of systems with structured uncertainties
Authors: Yasuda Yutaka
Published: July 2007

This paper considers a plant with structured uncertainties, such as one with a transfer function where the denominator and the numerator, respectively, are represented by a convex combination of two polynomials. A necessary and sufficient condition for the robust stabilization is presented, and the systematic design method for the compensator is shown.
SAW resonators using epitaxially grown Al electrodes
Authors: Ieki Hideharu , Sakurai Atsushi
Published: July 2007

Stress migration (SM) has become a serious issue with the development of surface acoustic wave (SAW) devices for high‐frequency application. For the first time, this paper discusses epitaxially grown Al electrode films as a countermeasure to SM. It also discusses a method of epitaxial growth of Al electrode films for an SAW resonator deposited onto quartz substrates. It is found that an epitaxially grown film has been fabricated under relatively moderate deposition conditions in vacuum evaporation. The orientation relation for this epitaxial growth is (311) «233»Al//(032)«100»SiO2. The SM lifetime for the SAW resonator thus obtained is found to be more than 2000 times longer and the allowable power value is improved by one order of magnitude more than that usually obtained for polycrystalline Al films with Cu. A discussion of the epitaxial growth mode and lifetime of electromigration also is presented.
Mobile communication systems and surface acoustic wave devices
Authors: Yamanouchi Kazuhiko
Published: July 2007

With the advent of a highly intelligent society, the role of mobile communication represented by the key words “anytime, anywhere, and with anybody” has become increasingly important. This paper describes mainly the mobile stations of the digital communication system in which the frequency‐use efficiency is improved significantly, as well as of analog mobile communication system. Also described are the surface acoustic wave devices, especially the low insertion loss filters, which are expected to be the key devices of mobile communication for small and lightweight equipment.
A low‐loss bandpass filter using SAW resonators
Authors: Satoh Yoshio , Ikata Osamu , Miyashita Tsutom , Matsuda Takashi , Nishihara Tokihiro
Published: July 2007

A filter structure having a ladder network of one‐port surface acoustic waves (SAW) resonators was studied, as a development of low‐loss, high‐frequency bandpass filters. A simulation tool was developed first and used for the design of the filters. It was found that the loss and the stopband attenuation can be controlled by the ratio of the capacitance for the parallel arm resonator Cop and that for the serial arm resonator Cos, i.e., CopCos. It was revealed also that the input and output impedances can be matched to 50 Ω by maintaining a certain relationship between Cop and Cos. Based on these findings, 900—MHz and 1.5—GHz RF filters were designed and prototyped for portable telephone applications. The 900—MHz filter has the insertion loss of 1.5 to 3 dB, the stopband attenuation of 20 to 30 dB, and the input output VSWR of less than 2, and requires no impedance matching circuit. Similar characteristics were achieved by the 1.5—GHz filter. The insertion loss turned out to be approximately half of what was achieved by the conventional transversal filters.
Solution of nonlinear simultaneous equation possessing transcendental functions by polynomial approximation method
Authors: Fujisaka Hisato , Sato Chikara
Published: July 2007

This paper presents a method of solving the simultaneous nonlinear equations containing transcendental functions in a specified domain. The features of the method are that the analysis can be executed in the complex domain by using the algebraic analysis and in the infinite range for the variable not contained in the transcendental function. The method is composed of the following procedures.

The specified domain of analysis is divided into subdomains, and the transcendental function is approximated by a polynomial in each subdomain. Using the computation algorithm for the Groebner basis, the single‐variable algebraic equation is derived and the number and the value of the approximate solution are determined. The computer algebra is applied to the computation process, and the efficiency of the calculation of the approximate solution is improved by deriving several polynomials called prime basis, together with the single‐variable equation.

To calculate the solution for the original equation based on the approximate solution, the techniques for numerical analysis such as Newton's method are employed. The reliability of the solution method is improved by the bifurcation analysis between the real and the complex‐valued solutions whenever necessary.
New cuts for width‐extensional mode quartz crystal resonators
Authors: Kawashima Hirofumi
Published: July 2007

This paper describes various characteristics for a width‐extensional mode quartz crystal resonator. A new cut is proposed for a width‐extensional mode quartz crystal resonator, which is designated the “KT‐cut,” and clarifies its frequency characteristics, frequency temperature behavior, and electrical characteristics.

First, a frequency equation is derived under the conditions that widthx0is much larger than thicknessz0but much smaller than lengthy0by solving partial differential equations for a new‐shape GT‐cut quartz crystal resonator already obtained with variational principle. This is because the modified shape for the present resonator is referred to as that of the new‐shape GT resonator.

Next, from the obtained equation, relationships of resonant frequency versus widthx0and the first‐ and second‐order temperature coefficients α, β versus a cut angle θ are analyzed theoretically. As a result, a cut angle θ which gives α = 0 approximately is θ = 24.5° at the reference temperature of 20°C and β has a value of β = −0.60 × 10−8/°C2. This value is then compared with the measured values of β = −1.25 × 10−8/°C2and the absolute value in the experiments is found to be about twice the calculated value. In addition, α and β are very dependent on a thickness‐to‐width ratioRzx(thicknessz0/widthx0), and have a parabolic curve versus the ratioRzx. Thus, α and β are also found to vary withRzx.

Finally, series resistanceR1, and a quality factorQare primarily examined in the frequency range of approximately 8.7 to 32 MHz. Consequently, e.g., whenf= 16.3 MHz, a width‐extensional mode quartz crystal resonator is found to be obtained successfully with satisfactory values ofR1= 89.7 Ω andQ= 180, 000.
TLR9 stimulation drives naïve B cells to proliferate and to attain enhanced antigen presenting function
Authors: Jiang Wei , Lederman Michael M. , Harding Clifford V. , Rodriguez Benigno , Mohner Richard J. , Sieg Scott F.
Published: July 2007

Mechanisms that regulate naïve B cell proliferation and function are incompletely defined. In this study, we test the hypothesis that naïve B cell expansion, survival and ability to present antigen to T lymphocytes can be directly modulated by Toll‐like receptor (TLR) agonists. In the absence of B cell receptor stimulation, CpG oligonucleotide, a TLR9 agonist, was particularly efficient in inducing naïve B cell proliferation and survival. Although the expanded naïve B cells did not mature into CD27+ or IgG+ memory B cells, these cells did differentiate into IgM‐secreting cells with increased surface expression of HLA‐DR, CD40 and CD80. This was associated with an increased potential for these B cells to activate allogeneic T cells. We propose that the activation and expansion of naïve B cells induced by TLR9 agonists could enhance the potential of these cells to interact with cognate antigens and facilitate cell‐mediated immune responses.
Enantiospecific Synthesis and Chiroptical Properties of Bicyclic Enones
Authors: Orentas Edvinas , Bagdžiūnas Gintautas , Berg Ulf , Žilinskas Albinas , Butkus Eugenijus
Published: July 2007

The enantiospecific synthesis of several bicyclic enones starting from enantiomerically pure (+)‐(1S,5S)‐bicyclo[3.3.1]nonane‐2,6‐dione (1) was accomplished. The target enones 7–9 were obtained in high yield and purity by using a catalytic amount of benzeneselenic anhydride. (+)‐(1S,5R)‐bicyclo[3.3.1]nonane‐2,3,6‐trione was obtained from diketone 1 by α‐hydroxylation involving the use of iodine under basic conditions. The reaction included a ring closure/reopening sequence via oxatricyclo[4.3.1.03,8]decane‐10‐one. It was shown that the latter triketone exists in enone/enol form. Chiroptical properties of the enantiomerically pure compounds were studied, and the sign of the Cotton effect was related to the absolute configuration of the enones. The positive Cotton effect in the bisignate CD curve is accounted for by the nonplanarity of the chromophore in enones (1S,5R)‐4 and (1S,5S)‐8. The circular dichroism spectra provided evidence for interchromophoric interaction in dichromophoric bis(enone) 9. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Isoxazoles and Isoxazolines by 1,3‐Dipolar Cycloaddition: Base‐Catalysed Condensation of Primary Nitro Compounds with Dipolarophiles
Authors: Machetti Fabrizio , Cecchi Luca , Trogu Elena , De Sarlo Francesco
Published: July 2007

1,4‐Diazabicyclo[2.2.2]octane (DABCO) or other suitable N‐bases cause primary activated nitro compounds to condense with alkenes to yield isoxazolines or with alkynes to give isoxazoles. As the molar ratio of the base with respect to the dipolarophile decreased, the reaction became slower, but the nitro compound became more resistant to hydrolytic cleavage. The best results were achieved with a molar ratio of base in the range of 0.05–0.1. The reactions were carried out in chloroform at 60 °C; for ethyl nitroacetate and phenylnitromethane, ethanol at 80 °C can be employed with better results and shorter reaction times. A catalytic cycle is proposed: in chloroform the hydrogen‐bonded ion pair formed between the nitronate and the protonated base undergoes reversible cycloaddition with the dipolarophile and then the hydrogen‐bonded intermediate adduct releases water by reaction with a second nitro molecule to give the product and the hydrogen‐bonded nitronate.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
A Convenient and General Method for the Synthesis of Indole‐2,3‐dicarboxylates and 2‐Arylindole‐3‐carboxylates
Authors: Sayyed Iliyas Ali , Alex Karolin , Tillack Annegret , Schwarz Nicolle , Michalik Dirk , Beller Matthias
Published: July 2007

A transition‐metal‐free, simple and efficient one‐pot method for the synthesis of indole‐2,3‐dicarboxylates and 2‐arylindole‐3‐carboxylates is described. The corresponding products are obtained by a domino hydroamination/Fischerindole cyclization in good‐to‐excellent yields from easily available 1‐alkyl‐1‐phenylhydrazines and acetylene carboxylates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
L‐Cysteine Voltammetry at a Carbon Paste Electrode Bulk‐Modified with Ferrocenedicarboxylic Acid
Authors: Raoof Jahan‐Bakhsh , Ojani Reza , Beitollahi Hadi
Published: July 2007

The electrochemical behavior of L‐cysteine studied at the surface of ferrocenedicarboxylic acid modified carbon paste electrode (FDCMCPE) in aqueous media using cyclic voltammetry, differential pulse voltammetry and double potential step chronoamperometry. It has been found that under optimum condition (pH 8.00) in cyclic voltammetry, the oxidation of L‐cysteine occurs at a potential about 200 mV less positive than that of an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, kh were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L‐cysteine showed a linear dependent on the L‐cysteine concentration and linear analytical curves were obtained in the ranges of 3.0×10−5 M–2.2×10−3 M and 1.5×10−5 M–3.2×10−3 M of L‐cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (3σ) were determined as 2.6×10−5 M and 1.4×10−6 M by CV and DPV methods.
Modelling of solute transport in a mild heterogeneous porous medium using stochastic finite element method: Effects of random source conditions
Authors: Chaudhuri A. , Sekhar M.
Published: July 2007

Randomness in the source condition other than the heterogeneity in the system parameters can also be a major source of uncertainty in the concentration field. Hence, a more general form of the problem formulation is necessary to consider randomness in both source condition and system parameters. When the source varies with time, the unsteady problem, can be solved using the unit response function. In the case of random system parameters, the response function becomes a random function and depends on the randomness in the system parameters. In the present study, the source is modelled as a random discrete process with either a fixed interval or a random interval (the Poisson process). In this study, an attempt is made to assess the relative effects of various types of source uncertainties on the probabilistic behaviour of the concentration in a porous medium while the system parameters are also modelled as random fields. Analytical expressions of mean and covariance of concentration due to random discrete source are derived in terms of mean and covariance of unit response function. The probabilistic behaviour of the random response function is obtained by using a perturbation‐based stochastic finite element method (SFEM), which performs well for mild heterogeneity. The proposed method is applied for analysing both the 1‐D as well as the 3‐D solute transport problems. The results obtained with SFEM are compared with the Monte Carlo simulation for 1‐D problems. Copyright © 2007 John Wiley & Sons, Ltd.
Development of new methods for asymmetric synthesis based on sulfoximines
Authors: Gais Hans‐Joachim
Published: July 2007

Sulfoximine‐substituted bis(allyl)titanium complexes, which are configurationally labile at the Cα‐atoms, have emerged as valuable reagents in asymmetric synthesis. Their highly selective reactions with aldehydes and N‐sulfonyl imino esters allow the attainment of enantio‐ and diastereomerically pure sulfoximine‐substituted homoallylic alcohols and homoallylic amines, respectively, which are valuable starting materials for the asymmetric synthesis of homopropargylic alcohols, 2,3‐dihydrofurans, medium‐sized carbocycles and lactones, unsaturated mono‐ and bicyclic prolines, β‐amino acids, and vinyl oxiranes, respectively. The high synthetic versatility of the sulfoximine group stems from its ability to function as a chiral carbanion‐stabilizing nucleofuge. © 2007 Wiley Periodicals, Inc. 18:472–481, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20331
Reactions of cysteine sulfenyl thiocyanate with thiols to give unsymmetrical disulfides
Authors: Alguindigue Nimmo Susan L. , Lemma Kelemu , Ashby Michael T.
Published: July 2007

Cysteine sulfenyl thiocyanate (CSSCN) reacts with thiols at pH 0 to cleanly yield disulfides. 2‐Mercaptoethanol (2‐MESH), 3‐mercaptopropionic acid (3‐MPASH), penicillamine (PENSH), and glutathione (GSH) react with CSSCN to give the corresponding mixed disulfides: 2‐MESSC, 3‐MPASSC, PENSSC, and GSSC. These compounds are stable at pH 0 and have been characterized by 1H and 13C NMR spectroscopy. © 2007 Wiley Periodicals, Inc. 18:467–471, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20340
Development of odorless organosulfur reagents and asymmetric reaction using odorless thiols
Authors: Node Manabu , Kajimoto Tetsuya
Published: July 2007

Odorless organosulfur reagents were developed by increasing their molecular weights to suppress volatility. 1‐Dodecanethiol (4), dodecyl methyl sulfide (5), p‐heptylphenylmethanethiol (6), p‐dodecylbenzenethiol (7), p‐heptylbenzenethiol (8), 2‐dodecyl‐1,3‐propanedithiol (11), p‐octyloxyphenyl‐methanethiol (18b), and p‐octyloxybenzenethiol (19) are typical examples of the odorless thiols and sulfides. 6‐Morpholinohexyl thiol (15), methyl 6‐morpholinohexyl sulfide (16), and methyl 6‐morpholinohexyl sulfoxide (17) were also developed as separable reagents from reaction products by facile acid‐base extraction. In addition, p‐tetramethylsilylphenylmethanethiol (18) and p‐tetramethylsilylbenzenethiol (14) were synthesized as the odorless synthetic substitutes of benzyl mercaptan and benzenethiol, respectively. In a similar way, silylated diphenyl disulfide (26) and diselenide (27) were prepared as odorless disulfide and diselenide. Moreover, 10‐sulfanylisoborneol (1) was found to be an excellent chiral odorless substitute of hydrogen sulfide in Michael addition. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:572–583, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20348
Healthy, wealthy and insured? The role of self‐assessed health in the demand for private health insurance
Authors: Doiron Denise , Jones Glenn , Savage Elizabeth
Published: July 2007

Both adverse selection and moral hazard models predict a positive relationship between risk and insurance; yet the most common finding in empirical studies of insurance is that of a negative correlation. In this paper, we investigate the relationship between ex ante risk and private health insurance using Australian data. The institutional features of the Australian system make the effects of asymmetric information more readily identifiable than in most other countries. We find a strong positive association between self‐assessed health and private health cover. By applying the Lokshin and Ravallion (J. Econ. Behav. Organ 2005; 56:141–172) technique we identify the factors responsible for this result and recover the conventional negative relationship predicted by adverse selection when using more objective indicators of health. Our results also provide support for the hypothesis that self‐assessed health captures individual traits not necessarily related to risk of health expenditures, in particular, attitudes towards risk. Specifically, we find that those persons who engage in risk‐taking behaviours are simultaneously less likely to be in good health and less likely to buy insurance. Copyright © 2007 John Wiley & Sons, Ltd.
Contrast‐enhanced MRI combined with MR cholangiopancreatography for the evaluation of patients with biliary strictures: Differentiation of malignant from benign bile duct strictures
Authors: Kim Ji Yang , Lee Jeong Min , Han Joon Koo , Kim Se Hyung , Lee Jae Young , Choi Jin Young , Kim Soo Jin , Kim Hyuck Jung , Kim Ki Hyeun , Choi Byung Ihn
Published: July 2007

Purpose

To determine imaging criteria for the combined use of contrast‐enhanced (CE)‐MRI and MR cholangiopancreatography (MRCP) to differentiate malignant from benign biliary strictures.

Materials and Methods

A total of 44 patients with biliary stricture who had undergone unenhanced, MRCP, and dynamic MRI were identified from radiological and surgical databases. Two radiologists analyzed MR features for asymmetry, luminal irregularity, abrupt narrowing, outer margin, signal intensity (SI) on T2‐weighted (T2W) images, and hyperenhancement relative to liver parenchyma during portal phase. The wall thickness and length of the narrowed segment were measured. MR findings relevant as predictors were identified using a Chi‐square or Fisher's exact test and the odds ratio (OR).

Results

The presence of hyperenhancement relative to liver parenchyma, length > 12 mm, wall thickness > 3 mm, indistinct outer margin, luminal irregularity, and asymmetry of strictured bile duct were significant factors for malignancy (P < 0.05). Malignant strictures were significantly thicker (5.0 ± 2.0 mm) and longer (27.0 ± 13.6 mm) than benign strictures. When any three or more of these six criteria were used in combination, we could identify 100% of malignant strictures and 87.0% of benign strictures.

Conclusion

The combined use of CE‐MRI and MRCP helped to define the criteria for differentiating malignant from benign biliary strictures in our data. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Chronic recurrent multifocal osteomyelitis (CRMO) with symmetric involvement of both femora: X‐ray, bone scintigram, and MR imaging findings in one case
Authors: Buck Florian M. , Treumann Thomas C. , Winiker Hermann , Strobel Klaus
Published: July 2007

The case of a 17‐month‐old boy with symmetric involvement of both femora in chronic recurrent multifocal osteomyelitis (CRMO) is presented. Imaging showed an extraordinary involvement of both femoral diaphyses and distal metaphyses with extensive lamellar‐like periosteal reactions. Diagnosis was based upon laboratory tests, bone scintigraphy, and MRI findings and was proved by open bone biopsy. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
In vivo MR imaging of bone marrow cells trafficking to atherosclerotic plaques
Authors: Qiu Bensheng , Gao Fabao , Walczak Piotr , Zhang Jiangyang , Kar Sourav , Bulte Jeff W.M. , Yang Xiaoming
Published: July 2007

Purpose

To develop a magnetic resonance imaging (MRI)‐based method to monitor in vivo trafficking of bone marrow (BM) cells to atherosclerotic lesions.

Materials and Methods

BM cells from LacZ‐transgenic mice were labeled with a superparamagnetic iron oxide (Feridex) and then transplanted into ApoE–/– recipient mice that were fed an atherogenic diet. Twenty‐four ApoE–/– mice were divided into three study groups: 1) group I with Feridex‐labeled BM transplantation (BMT) cells (N = 9), 2) group II with unlabeled BMT cells (N = 10), and 3) group III with no BMT cells (N = 5). Migrated Feridex/LacZ‐BM cells to atherosclerotic aortic walls were monitored in vivo using a 4.7T MR scanner and correlated with histopathological findings.

Results

In group I with Feridex‐BMT cells, histology examination displayed plaques in five of nine animals. In four of these five animals, in vivo MRI showed large MR signal voids of the aorta walls (due to the “blooming” effect of migrated Feridex‐BM cells in plaques), which were correlated with Feridex‐ and/or LacZ‐positive cells detected in the atherosclerotic lesions. No signal voids could be visualized in the two control animal groups (groups II and III).

Conclusion

This study demonstrates the potential use of in vivo MRI to monitor the trafficking of magnetically labeled BM cells to atherosclerotic lesions. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Behaviour of thujone during distillation and possible concentration ranges in pre‐ban absinthe
Authors: Lachenmeier Dirk W , Kuballa Thomas
Published: July 2007

A discrepancy in the magnitude of thujone concentrations in distilled pre‐ban absinthe has existed until now. Concentrations of 260 mg L−1 were derived at by theoretical calculations. Tests of authentic pre‐ban absinthes and studies concerning absinthes produced according to historic recipes found concentrations below 10 mg L−1. In this study, the behaviour of thujone during distillation was studied and a significant discrimination was determined (80% yield in water‐cum‐steam distillation). The thujone concentrations in distilled pre‐ban absinthe were then calculated with regard to the composition of wormwood derived from a literature review. Due to the large deviations of oil content and thujone concentration of wormwood, a typical Absinthe Suisse de Pontarlier from Duplais' 1855 recipe might have contained between zero and a maximum of 76 mg L−1 of thujone, the average was calculated as 23 mg L−1 with a standard deviation of 21 mg L−1. It was proven that the previous calculations overestimated the thujone content of distilled absinthe and the discrepancy was resolved as our new calculations are in good accord with the experimental findings. Copyright © 2007 Society of Chemical Industry
Selling adventure tourism: a distribution channels perspective
Authors: Schott Christian
Published: July 2007

This paper examines the distribution channels structure as well as the underlying factors influencing the most prominent channel choices within the adventure tourism industry. It is based on in‐depth interviews with adventure tourism operators in Queenstown, New Zealand. The findings suggest that the distribution structure is similar to other attraction sectors and that business size has some bearing on the ‘length’ of the distribution chains. However, regardless of business size, the sector places a clear priority on ‘at destination’ distribution, and the factors underlying this choice were found to be varied and reflective of both sector‐specific demand and supply characteristics. Copyright © 2007 John Wiley & Sons, Ltd.
A hybrid orthogonal TEM‐FED reflector antenna
Authors: Ho T. Q.
Published: July 2007

A novel feeding arrangement allows the parabolic reflector to radiate efficiently without the need of any loads or terminations. Radiation characteristics were examined over a 10:1 bandwidth. © 1993 John Wiley & sons, Inc.
Optical multiple‐variable fuzzy logic array using shadow casting
Authors: Lin Senmao , Zhang Shugun , Chen Caisheng , Kumazawa Itsuo
Published: July 2007

An optical area‐coded scheme is proposed to implement three‐variable fuzzy logic based on the shadow‐casting technique on one stage. In particular, no thresholding device is required. Experimental results are also given. © 1993 John Wiley & sons, Inc.
A free‐space double‐grid diplexer for a millimeter‐wave radiometer
Authors: Favreau M. , Goutoule J. M. , Orta R. , Savi P. , Tascone R.
Published: July 2007

We report on the design of a 45° incidence diplexer to be used in a millimeter‐wave radiometer. This equipment will be flown on a low‐orbiting satellite and should analyze the natural emissions of the Earth and the atmosphere in the bands around 90, 157, and 183 GHz. The diplexer has been realized with two grids of tripoles arranged in an equilateral triangular lattice and printed on both sides of a quartz slab. Experimental data are presented that are in good agreement with the theoretical predictions. © 1993 John Wiley & sons, Inc.
Threshold detection of nonorthogonal signaling in turbulent optical channels
Authors: Fares Doaa A.
Published: July 2007

The ever‐increasing demand for satellite links is motivating the search for techniques to enhance the utilization efficiency of optical communication systems. However, the performance of such a channel, in addition to background radiation and photodetector random gain, is highly affected by atmospheric turbulence along its propagation path. Multipulse nonorthogonal signaling has been recently introduced as a bandwidth‐efficient format for this channel [1]. In this article, threshold detection for this multipulse format is studied under different turbulence levels, concluding the optimum threshold setting for typical alphabet sizes. © 1993 John Wiley & sons, Inc.
Performance study of the reactively loaded power amplifier by transmission line modeling (TLM) with exponential switching resistance (ESR)
Authors: Chi‐Wai Cheung , Yu‐On Yam
Published: July 2007

A model combining transmission line modeling (TLM) and exponential switching resistance (ESR) of active devices is introduced in the equivalent circuit to simulate the real performance of the reactively loaded power amplifier. Using the TLM, the distributed circuit parameters can be controlled by the time step size, and the collector efficiency can be more accurately evaluated by introducing the ESR into the equivalent circuit. The TLM together with the ESR element provides a simple algorithm to be implemented, and is favorable for optimization of high‐efficiency performance in the rf range. © 1993 John Wiley & sons, Inc.
Measurement of the temporal coherence of an underwater optical scattered field
Authors: Arora K. , Sheybani E. O.
Published: July 2007

The coherence of a laser signal propagating through a turbid medium deteriorates due to scattering, affecting the performance of undereater coherent systems. The loss in coherence due to the scattering has been evaluated from the autocorrelation funcion obtained with an interoferometer followed by digital signal processing. © 1993 John Wiley & sons, Inc.
Millimeter‐wave FET frequency divider
Authors: Chen R. S.
Published: July 2007

In this article the theoretical and experimental performance of a FET harmonically synchronized frequency divider is presented. A large‐signal nonlinear characteristic transconductance description is adopted; the locking range can then be calculated by use of the method of averaging. The result is demonstrated by a common‐drain reverse‐channel GaAs FET frequency divider. © 1993 John Wiley & sons, Inc.
Evaluation of frequency‐selective reflector antenna systems
Authors: Wu T. K. , Lee S. W. , Zimmerman M. L.
Published: July 2007

The performance of a four‐frequency‐band (S/X/Ku/Ka) frequency‐selective surface (FSS) with double‐ring elements is evaluated both for a flat panel development and for a curved subreflector in a dual reflector antenna. Good agreement is observed between the measured and computed data for the flat panel FSS. To accurately predict the FSS effects on a dual reflector antenna's radiation pattern, we take into account the FSS subreflector's transmitted/reflected field variation as functions of the polarization and incident angles with respect to the local coordinates. An FSS transmission/reflection coefficient table is computed for TE and TM polarizations at various incident angles based on the planar FSS model. Next, the hybrid geometric optics (GO) and physical optics (PO) technique is implemented with linear interpolation of the FSS table to efficiencly determine the FSS effects in a dual reflector antenna. © 1993 John Wiley & sons, Inc.
Analog precorrection for improved‐accuracy optical matrix operations
Authors: Caulfield H. J.
Published: July 2007

If we are dealing with a fixed matrix which we want to use for matrix‐vector or matrix‐matrix operation and if we can measure the effective matrix represented, then we can often calculate a precompensating matrix which can also be implemented optically. This effectively squares the accuracy, e.g., from the typical 4 bits to 8 bits. © 1993 John Wiley & sons, Inc.
Model of the polarimetric behavior of chaff media
Authors: Pouliguen P. , Desclos L.
Published: July 2007

Since the early works on diffraction of chaff, there has been no mathematical modelization available for a real physical solution. This work presents one and gives a rigorous exploitation of the polarization behavior. One can find here a general model which can take into account all the phenomena appearing in a cloud of dipoles: the polarimetric effects, the mask, and the coupling influences. This development is new and can be generalized for clouds of spheres, discs, cylinders, or other simple shapes [1, 2]. © 1993 John Wiley & sons, Inc.