bluuebunny/crossref_metadata_2025 huggingface dataset:
The convergence of a PLL with variable parameters
Authors: Wullch Dov , Bar Moshe
Published: July 2007

A phase‐locked loop with variable parameters is considered. In such a system it is possible to obtain a short convergence time together with a small bandwidth. It is supposed that the PLL's parameters cannot be switched and there is a restriction on the velocity of the parameter variation.

An optimal strategy of parameter variation is obtained which gives an improvement in convergence time by a factor of about 30 in comparision to fixed parameter and small‐bandwidth PLLs.
A global delay model for domino cmos circuits with application to transistor sizing
Authors: Kang S. M. , Chen H. Y.
Published: July 2007

Domino CMOS circuits have played important roles in the design of high‐speed VLSI chips such as 32‐bit microprocessors and their family chips. Many researchers have worked on the characterization of the delay time and optimal design of domino CMOS circuits using circuit simulators as the main CAD tools. This paper presents a global analytical delay model for an important class of domino CMOS circuits wherein a multitude of n‐channel transistors form a series connection. the new model is shown to predict the delay time from the precharging clock edge to the 0.5 VDD output level with less than 10% error as compared to that from SPICE simulation over the entire design space. the delay model has been applied efficiently to the design automation of domino CMOS circuits modules.
Criteria for the existence of impulse responses and kernel representations for linear maps
Authors: Ball David , Sandberg Irwin W.
Published: July 2007

Results are given that establish, for the first time, necessary and sufficient conditions for the existence of impulse responses and kernel representations for linear not‐necessarily‐time‐invariant systems described by input‐output operator equations.

These results concern systems whose inputs and outputs are real‐valued functions on the real line R, the half‐line 10, ∞) or R″′. They deal with causal as well as non‐causal maps and considerably extend related previous results which concern causal maps defined on functions on the half‐line.
Curve‐search algorithm for DC analysis of non‐linear electronic circuits
Authors: Petrenko A. I. , Omer‐Imerely A. R.
Published: July 2007

The solution of the original DC analysis problem is reformulated as a search for a certain point in functional space which belongs to the curve in the same space. the generalized matrix equation of the hyperplane normal to this curve is easily derived and a new iterative algorithm is presented. Some critical situations arising in non‐linear circuit simulation and the behaviour of the new approach in these cases are considered. Six application examples are given.
A new biquadratic topology for mosfet‐C filters using non‐balanced structures
Authors: Liberatore A. , Manetti S. , Piccirilli M. C.
Published: July 2007

A new topology for the realization of MOSFET‐C integrated biquadratic filters is proposed which uses an MOS differentiator with non‐balanced structures. an interesting characteristic of the new topology is the possibility of realizing lowpass, bandpass and highpass filters with a one‐to‐one relationship between the biquadratic parameters and the circuit elements. This characteristic allows the implementation of programmable switchable filters.
Bounds on solutions of non‐linear resistive networks
Authors: Cel J.
Published: July 2007

Two methods for finding bounds on the solutions of some classes of resistive circuits containing non‐linear no‐gain resistors are presented. the magnitude of a voltage or current is shown to be bounded by its magnitudes appearing after replacement of all non‐linear devices by subcircuits consisting only of open‐ and short‐circuit elements. Examples of transistor circuits taken for comparison from the existing literature illustrate how the theorems work in practice.
Analysis of white and f−α noise in oscillators
Authors: Kaertner Franz X.
Published: July 2007

In this paper the general correlation spectrum of an oscillator with white and f‐αa noise sources is derived from the Langevin equations describing the deterministic and stochastic behaviour of an oscillator by perturbation methods. the treatment of f‐α noise and the influence of the finite measuring time on the noise spectra are included in a time domain calculation. the theory is applied to a Van der Pol oscillator exhibiting parametric sideband amplification and to a realized oscillator demonstrating the applicability of the theory to technically relevant circuits.
Fractal pattern of second‐order non‐linear digital filters: A new symbolic analysis
Authors: Chua L. O. , Lin T.
Published: July 2007

This paper studies the three‐valued symbolic dynamics associated with the second‐order non‐linear digital filter which has been shown to be a chaotic system recently. A new necessary and sufficient condition is given for a periodic sequence to be an admissible one. the condition is further used to prove that four types of periodic sequences cannot be admissible.
Realization of complex digital filters based on the LBC two‐pair extraction procedure
Authors: Acha José I. , Torres Francisco
Published: July 2007

The synthesis of real digital filters based on the lossless bounded real (LBR) two‐pair extraction procedure is extended to the complex domain. the only component then required is a first‐order reciprocal lossless bounded complex (LBC) two‐pair. This two‐pair permits the synthesis of any bounded complex (BC) or lossless bounded complex (LBC) digital transfer function. Lastly, a unitary implementation in terms of Givens (planar) rotation modules is given for the proposed two‐pair.
Measuring volterra kernels III: How to estimate the highest significant order
Authors: Chua Leon O. , Liao Youlin
Published: July 2007

Efficient methods were previously given for measuring the frequency‐domain transfer functions, namely Volterra kernels of weakly non‐linear systems. the success of these methods depends crucially on the assumption that the highest significant order of the system under test is known. Practical algorithms for determining the highest significant order of non‐linear systems are presented in this paper. Our algorithm can be used not only to validate the measurement results obtained by the methods presented earlier but is also capable of determining whether a Volterra series representation actually exists for the system under test.
On the design of 1D IIR digital filters with coefficients of finite word length
Authors: Papamarkos N. , Vachtsevanos G.
Published: July 2007

This paper presents new linear programming techniques for the design of optimal 1D IIR digital filters. the first method is based on a linear minimax criterion and leads to a linear programming approximation problem whose optimal solution is attained by a new fast algorithm. Next, the linear minimax approximation problem is extended and formulated as two linear integer programming problems which permit the design of 1D IIR digital filters with coefficients of finite word length. the first of these methods is formulated as a 0‐1 integer linear programming problem and its optimal solution is attained rapidly by a new algorithm. This method appears to be suitable for the design of high‐order digital filters. the second method is more general and is formulated as a mixed integer linear programming problem. to solve the design problem efficiently, a new integer tree search algorithm is introduced. the feasibility of the proposed algorithms is illustrated with detailed solutions or numerical examples.
Time‐varying analogue constrained notch filter
Authors: Wulich Dov
Published: July 2007

The idea of discrete constrained notch filters is well known and widely described in the literature. Time‐invariant as well as time‐varying filters are considered. Because of the discrete nature of such filters, their application is limited to sampled signals, usually obtained as samples of low‐frequency signals. the aim of this paper is to give some ideas on how to synthesize a time‐varying analogue constrained notch filter which can be used directly for continuous signals.
Multilevel and non‐ideal quantization in ∑ δ modulation
Authors: Feely Orla , Chua Leon O.
Published: July 2007

Oversampled sigma‐delta analogue‐to‐digital conversion has been the focus of much research attention in recent years. Converters based on this principle have been found to be particularly suited to integrated circuit implementation owing to their simple structure and robustness to circuit imperfection. the analysis of the sigma‐delta system is complicated by the presence of a discontinuous non‐linear element, with the result that until very recently few rigorous studies of such converters had appeared in the literature.

In this paper we study the operation of the single‐loop sigma‐delta modulator, consisting of a quantizer and a discrete‐time integrator in a feedback loop, with constant input. Our analysis uses the tools of non‐linear dynamics to derive rigorous descriptions of system behaviour. In particular we focus on the effects of the discontinuous nonlinear element‐the quantizer. In the most basic case the quantizer has two levels. We study the effect of quantizer offsets in conjunction with leaky integration on the behaviour of this system. We then study the effect on system operation of increasing the number of quantization levels and explain in quantitative terms the structure of the resultant input versus average output characteristic.
Cellular neural network for fast adaptive equalization
Authors: Perfetti Renzo
Published: July 2007

The use of an analogue neural network in the adaptive equalization of time‐varying communication channels is proposed. the network is used to compute the coefficients of a linear transversal filter. the settling time decreases as the filter order increases and as the signal‐to‐noise ratio decreases. Owing to the real‐time processing capabilities, the network can be useful when it is of interest to track fast variations, as in radio links. the special properties of the tap input correlation matrix result in a cellular network architecture which greatly simplifies the VLSI implementation. Simulation results are presented which point out very satisfactory performance.
Circuit theoretic approach to the tank‐hopfield A/D converter
Authors: Martinelli G. , Perfetti R.
Published: July 2007

The ‘neural’ A/D converter of Tank and Hopfield is analysed from the viewpoint of circuit theory. It is shown to be a particular case of the canonical non‐linear programming circuit of Chua and Lin. Several qualitative properties concerning the DC solutions are proved. A piecewise‐linear analysis of trajectories in the state space is carried out on the basis of the eigenvalues and eigenvectors of the corresponding dynamical matrix. It is shown that the eigenvalues are related to the driving point impedance of an RC one‐port network. Asymptotic expressions of the eigenvalues are derived for large N, N being the number of bits. It is shown that the dynamic behaviour represents a sort of successive‐approximation A/D conversion. However the conversion time does not increase appreciably as the number of bits increases. the cases of incorrect behaviour and the amount of the maximum conversion error are derived for N > 5. Simulation results are presented for N ≤ 5.
Switched capacitor circuit for 1/f noise generation using a power‐law circuit
Authors: Murao Kenji , Kohda Tohru
Published: July 2007

A simple switched capacitor (SC) circuit is given which realizes a one‐dimensional discrete dynamical system Xn+1 = Xn + uxz generating intermittent chaos with a 1/f‐shaped power spectrum. an integrated circuit with a pair of logarithmic and antilogarithmic amplifiters can easily realize the power‐law term xz which plays a key role in generating l/fnoise. an inevitable small offset voltage ϵ in the SC circuit governs the cut‐off frequency of 1/f noise, and when the dynamical system is modified by introducing an effective ϵ, the ‘indirect method’ enables us to get the precise power spectrum in the modified system.
Chaos from a buck switching regulator operating in discontinuous mode
Authors: Tse C. K.
Published: July 2007

A first‐order iterative map which describes the dynamics of a simple feedback buck switching regulator operating in discontinuous mode is derived. Analysis of this map shows that flip bifurcations occur at certain values of the feedback factor. Results from computer simulations and experiments reveal that the system exhibits a typical perioddoubling route to chaos under the particular operating condition studied in this paper. It is found that a special kind of randomness, arising from the ability of the system to ‘merge’ and ‘skip’ periods, constitutes a unique feature of the chaotic dynamics of switched‐mode converter circuits.
Exact solutions of cyclically symmetric oscillator equations with non‐linear coupling
Authors: Fox David
Published: July 2007

Kaplan and Yardeni have found very simple exact limit cycle solutions in cyclically symmetric systems of N oscillator equations with linear coupling in zero order of a perturbation parameter and non‐linear coupling in first order. In contrast with such solutions in other non‐linear systems, each of these limit cycles is a normal mode of the unperturbed equations, with no change in frequency. the sources of this simple behaviour are studied here with the equations expressed in terms of the normal mode co‐ordinates of the unperturbed system rather than in the original co‐ordinates. It is found that the simplicity of the Kaplan‐Yardeni solutions arises partly from an additional symmetry of the perturbation terms beyond the cyclic symmetry and partly from the specific choices of the perturbations. Extension of their systems to arbitrary N leads to the result that all such sets of equations have similar simple limit cycles. More general cyclically symmetric sets of equations are also discussed, with limit cycle solutions whose frequencies are shifted from the zero‐order values by easily calculated amounts or with solutions which are linear combinations of zero‐order normal modes.
A general approach to circuit equations
Authors: Tuma T. , Bratkovič F.
Published: July 2007

Computer‐aided circuit analysis is a complex procedure which may be roughly divided into three steps. the first stage is device modelling, where quantitative properties of the participating electronic devices are determined. In the second step the circuit's topology in conjunction with the device equations is exploited in order to formulate a linearized nonsingular equation set. Eventually the equation set is solved iteratively in the third phase, yielding a solution vector of circuit variables.

This paper deals with the second and third steps, where diverse sparse matrix methods are employed. Its aim is to provide a general mathematical form by which most matrix manipulation techniques can be described, thus enabling their classification on a theoretical level. Usually these methods are presented descriptively rather than strictly mathematically.

The paper introduces a matrix reduction operator from which a general matrix operator equation is deduced. This operator equation can be used to describe entire analysis approaches. After some necessary definitions, the purpose of this paper is illustrated by studying several classical examples rather than giving many mathematical proofs. the selected examples involve some well‐known linear equation set solution methods as well as several typical equation set transformations.
A state space approach to the tangential interpolation problem with bounded real matrices
Authors: Piekarski Marian S. , Uruski Marceli
Published: July 2007

This paper presents a global solution of the tangential interpolation problem via state space concepts. the solution is obtained in two steps. the first step consists of factorization of the Nevanlinna‐Pick matrix and calculating the state space vectors of a passive n‐port network N. In the second step, using the state space vectors and the interpolation data, a passive minimal state space realization of N is derived from which the desired interpolating bounded real matrix is obtained. the presented approach involves only standard algebraic matrix procedures and provides the constructive algorithm for the interpolating matrix.
Simplified impedance broadband matching by the image parameter method: The RC case
Authors: Dehollain Catherine , Neirynck Jacques
Published: July 2007

The image parameter theory is now considered as outdated for filter design owing to the existence of very efficient optimization procedures for the effective behaviour of filters. Nevertheless, it allows one to exhibit very simple relations between the bandwidth and the values of the components. Hence it is ideally suited for the problem of impedance broiband matching where the bandwidth and some components are specified data. It is shown that it allows to make a straightforward distinction between well‐ and ill‐conditioned problems. In the first case the problem is reduced to a one‐dimensional optimization and an image parameter design provides very easily an equalizer optimal for all practical purposes. In the second case the values of the image parameter design provides excellent initial values for an optimization process.

The method is applied here to the simplest problem, the RC load. In a separate paper it will be shown that it is easily extended to more complicated loads and the double‐matching problem.
Meixner‐like functions having a rational z‐transform
Authors: Brinker A. C. Den
Published: July 2007

Square‐summable causal functions can be expressed in a Meixner series. In principle, approximate filter synthesis is thus possible. However, Meixner filters are not realizable since the Meixner functions do not have a rational z‐transform. A set of orthonormal functions is constructed with the following properties. Like the Meixner functions, these functions are a generalization of the discrete Laguerre functions and they have a polynomial character as well. In contrast with the Meixner functions, they have the desired property of a rational z‐transform.
An analogue module generator for mixed analogue/digital asic design
Authors: Gielen G. , Debyser G. , Lampaert K. , Leyn F. , Swings K. , Van Plas G. Der , Sansen W. , Leenaerts D. , Veselinovic P. , van Bokhoven W.
Published: July 2007

This paper discusses the realization of an analogue module generator that forms part of a mixed analogue/digital design environment. It is able to design analogue functional modules such as like amplifiers, filters, etc., either in an automatic or in an interactive session, starting from performance specifications over topology selection, parameter optimization and simulation/verification down to lay‐out. the analogue module generator is integrated in a commercial EDA framework. Practical design results show the capabilities and efficiency of the system.
A discrete‐time approach to the steady state analysis and optimization of non‐linear autonomous circuits
Authors: Palà‐schönwälder Pere , Mirö‐sans J. M.
Published: July 2007

In this paper a method for the steady state analysis and optimization of non‐linear autonomous circuits is described. After discretizing the linear part of the circuit, a system of non‐linear algebraic equations is obtained. the final formulation is written entirely in the discrete‐time domain, making it unnecessary to repeatedly take direct and inverse DFTs during the solution process. Furthermore, it is shown that the resulting formulation may be viewed as a generalization of the harmonic balance equations. an analytic method for computing the exact partial derivatives of the resulting equations with respect to the samples of the variables, the oscillation period and the circuit element values is described, making the proposed approach efficient for both analysis and optimization. Different globally convergent techniques for solving the non‐linear system of equations are described, with emphasis on an algorithm based on fast simulated diffusion. Selected application examples are provided to validate the proposed approach.
Symbolic compaction with analogue constraints
Authors: Malavasi Enrico , Felt Eric , Charbon Edoardo , Sangiovanni‐Vincentelli Alberto
Published: July 2007

A tool named SPARCS‐A for compaction of integrated circuits with analogue constraints is presented. the approach is structured in two steps. First a robust and efficient constraint graph compaction algorithm produces a compacted layout quickly, where parasitics are controlled so as to guarantee that the performance constraints are met. Next the layout produced by the first step is fed into a linear programming (LP) solver which enforces symmetries and performs global interconnect length minimization. the computational cost of the iterative LP solver is modest, because its initial state is the configuration found by the constraint graph algorithm and only symmetry constraints need to be enforced. With considerable computational efficiency this algorithm produces a compacted layout which satisfies the high‐level performance constraints and is feasible for practical use within industrial‐strength analogue synthesis systems. the use of such a compactor allows one to relax the requirements on parasitic control during placement and routing, thus improving the efficiency of the entire layout design process.
The analogic cellular neural network as a bionic eye
Authors: Werblin Frank , Roska Tamás , Chua Leon O.
Published: July 2007

The conception of the CNN universal machine has led quite naturally to the invention of the analogic CNN bionic eye (henceforth referred to simply as the bionic eye). the basic idea is to combine the elementary functions, the building blocks, of the retina and other 2 1/2 D sensory organs, algorithmically, in a stored programme of a CNN universal machine, through the use of artificial analogic programmes. the term bionic is defined in a rigorous way: it is a nonlinear, dynamic, spatiotemporal biological model implemented in a stored programme electronic (optoelectronic) device; this device is in our case the analogic CNN universal machine (or chip).

The aim of this paper is to report on this new invention, particularly to electronic and computer engineers, in a tutorial way.

We begin by summarizing (1) the biological aspects of the range of retinal function (the retinal universe), (2) the CNN paradigm and the CNN universal machine architecture and (3) the general principles of retinal modelling in CNN. Next we describe new CNN circuit and template design innovations that can be used to implement physiological functions in the retina and other sensory organs using the CNN universal machine. Finally we show how to combine given retinal functional elements implemented in the CNN universal machine with analogic algorithms to form the bionic retina. the resulting system can be used not only for simulating biological retinal function but also for generating functions that go far beyond biological capabilities. Several bionic retina functions, different topographic modalities and analogic CNN algorithms can then be combined to form the analogic CNN bionic eye. the qualitative aspects of the models, especially the range of dynamics and accuracy considerations in VLSI optoelectronic implementations, are outlined. Finally, application areas of the bionic eye and possibilities of constructing innovative devices based on this invention (such as the bionic eyeglass or the visual mouse) are described.
Simultaneous generation of fra‐2 conditional and fra‐2 knock‐out mice
Authors: Eferl Robert , Zenz Rainer , Theussl Hans‐Christian , Wagner Erwin F.
Published: July 2007

Loss of function mouse models comprise knock‐out mice, where a gene is deleted in the germline, and conditional knock‐out mice with somatic deletion of a floxed allele in defined tissues. Both types of mice are used for comprehensive studies of gene functions in vivo. Here, we describe a simple method for simultaneous generation of mice with conditional or knock‐out alleles for the transcription factor fra‐2 (Fos‐related antigen 2) using a single embryonic stem (ES) cell clone. ES cells with a floxed fra‐2 allele were transiently transfected with a Cre‐recombinase expression plasmid and plated at low density. Most of the resulting ES cell colonies consisted of a mixture of cells that have either retained or lost the conditional allele. We demonstrate that these mixed ES cell clones can be directly used for generation of chimeras that give rise to offspring with conditional or knock‐out alleles simultaneously. This strategy shortens the time and reduces the number of germline transmission events to generate genetically modified mice. genesis 45:447–451, 2007. © 2007 Wiley‐Liss, Inc.
When positive and negative expectancies disrupt performance: regulatory focus as a catalyst
Authors: Keller Johannes , Bless Herbert
Published: July 2007

The present research investigates the impact of negative and positive stereotypic expectancies on cognitive test performance. A theoretical framework that relates expectancy effects to self‐regulatory processes as postulated by Regulatory Focus Theory (RFT) is presented. Building on the differential sensitivity hypothesis proposed in this theoretical model, we argue that when self‐regulation in a prevention focus is activated individuals are particularly sensitive with regard to negative cues and therefore negative expectancies are likely to result in poor test performance due to an apprehension about meeting minimal goal standards. Conversely, when self‐regulation is guided by a promotion focus individuals are particularly sensitive with regard to positive cues and hence likely to show impaired performance when confronted with positive expectancies due to an apprehension about meeting maximal goal standards. The results of four experiments, relying on both situational and chronic regulatory focus, support these assumptions. Copyright © 2007 John Wiley & Sons, Ltd.
Coating of open tubular capillaries with discoidal and spherical high‐density lipoprotein particles in electrochromatography
Authors: Vainikka Kati , Chen Jie , Metso Jari , Jauhiainen Matti , Riekkola Marja‐Liisa
Published: July 2007

A new method was developed for the coating of fused‐silica capillaries with human high‐density lipoproteins (HDLs) for use in electrochromatography. The HDL particles used for the coating differed in particle shape and composition. Both discoidal and spherical particles formed a monolayer on the inner silica wall as confirmed by atomic force microscopy. The effect of coating conditions, such as HDL concentration and coating time, was investigated with spherical HDL particles. Examination of the influence of pH on the coating stability also allowed the determination of pI values for the HDL particles attached to the capillary wall. The pI values for spherical and discoidal HDL particles were close to 5.0. The repeatabilities of the EOF mobility and the retention factors of the uncharged steroid hormones used as model compounds were exploited in the evaluation of the coating stability. The optimal coating was achieved with 0.1 mg/mL HDL protein and 50 min flushing with coating solution followed by 15 min standing time. Electrochromatography with HDL‐coated open tubular capillaries offers a new tool for the study of HDL particle structure and transformations.
Voltage‐assisted capillary LC of peptides using monolithic capillary columns prepared by ring‐opening metathesis polymerization
Authors: Sedláková Pavla , Miksik Ivan , Gatschelhofer Christina , Sinner Frank M. , Buchmeiser Michael R.
Published: July 2007

We examined the use of monolithic capillary columns prepared via ring‐opening metathesis polymerization (ROMP) for peptide separation in voltage‐assisted capillary LC (voltage‐assisted CLC). In order to demonstrate their potential for peptide separation, ROMP‐derived monoliths with RP properties were prepared. The preparation procedure of monoliths was transferred from ROMP monoliths optimized for CLC. ROMP monoliths were synthesized within the confines of 200 μm id fused‐silica capillaries with a length of 37 cm. After optimization of the chromatographic conditions, the separation performance was tested using a well‐defined set of artificial peptides as well as two peptidic mixtures resulting from a tryptic digest of BSA as well as a collagenase digest of collagen. ROMP monoliths showed comparable performance to other monolithic separation media in voltage‐assisted CLC published so far. Therefore, we conclude that by optimizing the composition of the ROMP monoliths as well as by using the controlled manner of their functionalization, ROMP monoliths bear a great potential in CLC and CEC.
Carer burden in dementia—assessing the impact of behavioural and psychological symptoms via self‐report questionnaire
Authors: Neil Wendy , Bowie Peter
Published: July 2007

Background

The relationship between the behavioural and psychological symptoms of dementia (BPSD) and negative outcomes in carers has been consistently demonstrated, however the quality of the assessment of the former in routine clinical settings is variable and validated interview‐based scales are frequently underutilised.

Aims

To develop a carer self‐report questionnaire, the Behavioural and Psychological Symptoms Questionnaire (BPSQ), for the assessment of the neuropsychiatric symptoms of dementia and associated carer distress.

Method

The BPSQ was administered to the carers of 30 community‐dwelling older adults with diagnoses of Alzheimer's or vascular dementia and the results compared with interview assessment using the Neuropsychiatric Inventory (NPI).

Results

BPSD were present in 96.2% of patients. There was strong correlation (rs = 0.61, p < 0.001) between the BPSQ and interview with respect to measures of symptom frequency and severity. However, there was significant divergence between the two assessment schedules with respect to carer distress which was found to be significantly under‐reported in the initial interview (U = 64.00, z = −5.22, p < 0.0001).

Conclusions

The BPSQ is an effective tool to complement clinical interview in the assessment and monitoring of BPSD, and provides useful additional information with respect to carer distress, which currently may be under recognised. A follow‐up study is required to complete the work of validating the BPSQ. Copyright © 2007 John Wiley & Sons, Ltd.
Environmental controls on evapotranspiration from sparse grassland in Mongolia
Authors: Zhang Yinsheng , Kadota T. , Ohata T. , Oyunbaatar D.
Published: July 2007

Environmental controls on evapotranspiration were investigated at a sparse grassland in Mongolia during 2003 and 2004. The study site was located on the southern periphery of the Eurasian cryosphere. Data from Eddy covariance, aerodynamic, and manual measurements were used in the analysis. A decoupling factor (Ω) was calculated to determine the relative importance of surface conductance and radiation to change in evapotranspiration rates. Higher evapotranspiration rates associated with a higher frequency of large Ω values revealed the importance of radiation forcing on evapotranspiration at this study site. As Ω increases', the aerodynamic conductance (ga) increased correspondingly but vegetation conductance (gC) decreased. Aerodynamic conductance (ga) was well fitted to an exponential function of the wind stress; gC clearly decreased as the vapour pressure deficit (d) increased; gC related to air temperature through d. Although grass cover was sparse at the study site, the anticipated effect of soil moisture on E and gS was only slightly suggested and thus not deducible. On the 10‐day‐interval time scale, the effect of vegetation cover on evapotranspiration was insignificant compared to that of surface soil moisture. Changes in soil evaporation, related to precipitation, mainly caused the very large inter‐annual differences in evapotranspiration. The relationship between evapotranspiration and surface bulk resistance at the study site could therefore be fit to an exponential function. Copyright © 2007 John Wiley & Sons, Ltd.
Wind direction dependency of water and energy fluxes and synoptic conditions over a tundra near Tiksi, Siberia
Authors: Kodama Yuji , Sato Norifumi , Yabuki Hironori , Ishii Yoshiyuki , Nomura Mutsumi , Ohata Tetsuo
Published: July 2007

In order to better understand the water cycle over tundra, micro‐meteorological observations were carried out over tundra near Tiksi, northeastern Siberia, and seasonal variations in the energy budget components were estimated for a period of 2 years. As an average for 1998 and 1999, net radiation was partitioned into a sensible heat flux of 25–30%, to a latent heat flux of 50–55%, and to a soil conductive heat flux of 15–25%. These ratios were changed by wind direction. The southwesterly winds were warm and dry, reducing sensible heat flux or changing its direction towards the ground surface, while northeasterly winds were cold, resulting in a sensible heat flux into the atmosphere from the tundra surface. Southwesterly winds were associated with cyclone intrusions into this area, and northeasterly winds were associated with anti‐cyclones. More frequent intrusions of cyclones would decrease the sensible heat flux and increase the latent heat flux. Copyright © 2007 John Wiley & Sons, Ltd.
Fibroin/collagen hybrid hydrogels with crosslinking method: Preparation, properties, and cytocompatibility
Authors: Lv Qiang , Hu Kun , Feng QingLing , Cui Fuzhai
Published: July 2007

Substrate stiffness is an important physical factor in the response of many cell types. Although protein‐based hydrogels are widely used as cell‐culture substrates because of their resemblance to the natural extracellular matrix (ECM) and complex signaling, their rigidity should be further increased to facilitate the adhesion and growth of cells. In this study, fibroin/collagen hydrogels having suitable stiffness were prepared directly by adding 1‐ethyl‐3‐(3‐dimethylaminoprophy) carbodiimide hydrochloride (EDC) in fibroin/collagen solution to induce crosslinking. The storage moduli of these crosslinked hydrogels are above 3 kPa, and even exceed 10 kPa, having stronger mechanical strength than that of previously reported protein‐based hydrogels. Furthermore, the crosslinked hydrogels can maintain their configuration above 80oC, which proves their increased thermal stability. Although crosslinked, the hydrogels still maintain the mobility of fibroin molecules. The growth of vascular smooth muscle cells (VSMCs) in fibroin/collagen gels indicates that the crosslinking reaction has no negative influence on the biocompatibility of fibroin/collagen hydrogels. The fibroin/collagen hydrogels are more propitious to the growth of cells compared with fibroin/collagen scaffolds. Because of their inherent biocompatibility, excellent mechanical and thermal properties, and green preparation process, the fibroin/collagen hydrogels would become promising scaffolds for tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
The degradation profile of novel, bioresorbable PCL–TCP scaffolds: An in vitro and in vivo study
Authors: Yeo A. , Rai B. , Sju E. , Cheong J.J. , Teoh S.H.
Published: July 2007

Degradation studies of scaffolds are important in bone tissue engineering. Previously, novel poly(ε‐caprolactone)–20% tricalcium phosphate (PCL–TCP) based scaffolds were developed and proven useful for bone regeneration. In this study in vitro degradation analyses were carried out with the PCL–TCP scaffolds immersed in standard culture medium for 24 weeks. In vivo degradation was performed with the scaffolds implanted in the abdomen of rats for the same period of time. Results demonstrated greater degradation of PCL–TCP scaffolds in vivo than in vitro. At 24 weeks, the increase of average porosity of the scaffolds in vivo was 29.2% compared to 2.65% in vitro. Gel permeation chromatography (GPC) analysis revealed a decrease of 29% and 20% respectively in the Mn and Mw values after 24 weeks in vitro. However, a significant decrease in Mn and Mw values (79.6% and 88.7% respectively) were recorded in vivo. The mechanical properties however, were relatively similar and closely match those of cancellous bone even at 24 weeks. The results showed that the scaffold can be used for dentoalveolar reconstruction and PCL–TCP scaffolds have shown to possess the potential to degrade within the desired time period of 5–6 months and favorable mechanical properties. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Substitution effect on the geometry and electronic structure of the ferrocene
Authors: Zhang Guiling , Zhang Hui , Sun Miao , Liu Yanhong , Pang Xiaohong , Yu Xiaoyang , Liu Bo , Li Zesheng
Published: July 2007

The substitution effects on the geometry and the electronic structure of the ferrocene are systematically and comparatively studied using the density functional theory. It is found that NH2and OH substituents exert different influence on the geometry from CH3, SiH3, PH2, and SH substituents. The topological analysis shows that all the CC bonds ina–gare typical opened‐shell interactions while the FeC bonds are typical closed‐shell interactions. NBO analysis indicates that the cooperated interaction of d → π* and feedback π → d + 4s enhances the Fe‐ligand interaction. The energy partitioning analysis demonstrates that the substituents with the second row elements lead to stronger iron‐ligand interactions than those with the third row elements. The molecular electrostatic potential predicts that the electrophiles are expected to attack preferably the N, O, P, or S atoms in FerNH2, FerOH, FerPH2, and FerSH, and attack the ring C atoms in FerSiH3and FerCH3. In turn, the nucleophiles are supposed to interact predominantly by attacking the hydrogen atoms. The simulated theoretical excitation spectra show that the maximum absorption peaks are red‐shifted when the substituents going from second row elements to the third row elements. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Evaluation of different doses of UV irradiation to loach eggs for Genetic inactivation of the maternal genome
Authors: Fujimoto Takafumi , Sakao Suzu , Yamaha Etsuro , Arai Katsutoshi
Published: July 2007

Genetic inactivation of the egg nucleus is an indispensable step in the production of androgenetic embryos in teleosts. However, few experimental studies have focused on determining the most effective means of achieving complete inactivation of the maternal genome. Here, we sought to identify the optimum conditions of ultraviolet (UV) irradiation for complete inactivation of the loach egg nucleus. Unfertilized eggs were UV irradiated from above with a dose in the range 0–200 mJ/cm2. Successful inactivation of the maternal genome was evaluated by the exclusive expression of a paternally inherited color phenotype. The presence or absence of putative maternal chromosome fragments was screened by flow cytometry of DNA content and by cytogenetic analysis. The majority of the larvae derived from irradiated eggs had an abnormal appearance. Haploid individuals were detected by measurement of DNA content flow cytometry and by chromosome counting in the groups that received more than 75 mJ/cm2 groups. Although the coefficient of variation of DNA content was apparently reduced in the 125–200 mJ/cm2 groups, chromosome fragments were still detected in all the groups from irradiated eggs. Inactivation of the egg nucleus was also histologically elucidated by the presence or absence of residual nuclear material in anuclear embryos that developed from UV‐irradiated eggs fertilized with UV‐irradiated sperm. Embryos that were completely or near‐completely anuclear were found in the 150 and 200 mJ/cm2 groups. We conclude that the optimum UV dose for complete genetic inactivation of the egg nucleus is more than 150 mJ/cm2. J. Exp. Zool. 307A:449–462, 2007. © 2007 Wiley‐Liss, Inc.
Characterization of the protein profile of donkey's milk whey fraction
Authors: Cunsolo Vincenzo , Saletti Rosaria , Muccilli Vera , Foti Salvatore
Published: July 2007

Characterization of the protein profile of the whey fraction from a milk sample taken from an individual donkey belonging to the ‘Ragusana’ species of the East of Sicily is reported. Direct RP‐HPLC/electrospray ionization (ESI)‐MS analysis of the whey fraction allowed the detection of some unknown components, together with the identification of already known whey proteins. Matrix‐assisted laser desorption/ionization (MALDI)‐TOF/MS and RP‐HPLC/ESI‐MS/MS analysis of the enzymatic digests of the unknown components resulted the identification and characterization of (1) two β‐casein fragments; (2) the sequence of donkey's serum albumin; and (3) the oxidized methionine forms of lysozyme B and α‐lactoalbumin. One of the two β‐casein fragments corresponds to the sequence Val176‐Arg189 of the horse's β‐casein. The second one corresponds the C‐terminal sequence Tyr199‐Val226 of the horse's β‐casein, with four amino acid substitutions (Q → R203, L/I → P206, F → L210 and P → A219). Both fragments, reasonably arising by endogenous proteases cleavage of the donkey's β‐casein, could be potential biologically active peptides. Direct mass spectrometric sequence characterization of the detected donkey's serum albumin reveals the presence of the amino acid substitution Val → Ile at position 497 with respect to the cDNA deduced sequence. The oxidized forms of lysozyme B and α‐lactoalbumin are selectively oxidized at methionine 79 and methionine 90, respectively. Copyright © 2007 John Wiley & Sons, Ltd.
Raman spectroscopic investigation of pure and ytterbium‐doped rare earth silicate crystals
Authors: Zheng Lihe , Zhao Guangjun , Yan Chengfeng , Xu Xiaodong , Su Liangbi , Dong Yongjun , Xu Jun
Published: July 2007

Raman spectroscopy was used to study the molecular structure of a series of selected rare earth (RE) silicate crystals including Y2SiO5 (YSO), Lu2SiO5 (LSO), (Lu0.5Y0.5)2SiO5 (LYSO) and their ytterbium‐doped samples. Raman spectra show resolved bands below 500 cm−1 region assigned to the modes of SiO4 and oxygen vibrations. Multiple bands indicate the nonequivalence of the REO bonds and the lifting of the degeneracy of the RE ion vibration. Low intensity bands below 500 cm−1 are an indication of impurities. The (SiO4)4− tetrahedra are characterized by bands near 200 cm−1 which show a separation of the components of ν4 and ν2, in the 500–700 cm−1 region which are attributed to the distorting bending vibration and in the 880–1000 cm−1 region which are attributed to the symmetric and antisymmetric stretching vibrational modes. The majority of the bands in the 300–610 cm−1 region of Re2SiO5 were found to arise from vibrations involving both Si and RE ions, indicating that there is considerable mixing of Si displacements with SiO bending modes and REO stretching modes. The Raman spectra of RE silicate crystals were analyzed in terms of the molecular structure of the crystals, which enabled separation of the bands attributed to distinct vibrational units. Copyright © 2007 John Wiley & Sons, Ltd.
New task for a legislature
Authors: Bebout John E.
Published: July 2007

Citkena of New Jersey direct their 1944 senators and assemblymen to undertake revision of state's century‐old constitution for submission to voters in November.
Researcher's digest: January
Authors: Roher Miriam
Published: July 2007

All about Kalamazoo; how to write an employee manual, also a good municipal report; Minnesota administration analysed; guide to data on cities; Michigan highway report; pot pourri.
Dallas prepares for the future
Authors: Smitham V. R.
Published: July 2007

Well accustomed to looking ahead since its pioneer effort of 1911, Texas metropolis in drafting a complete master plan to guide city's growth for the next quarter century.
Researcher's digest: February
Authors: Roher Miriam
Published: July 2007

Measurement applied by metropolitan consolidation; what the public in thinking on postwar problems; taxes and business reserves; South Dakota surveys local salaries.
Cities get ‘out of red’ together
Authors: Biesen Chester
Published: July 2007

Some two hundred municipalities, organized in 1933 as the Association of Washington Cities, help to develop a well rounded tax structure and thereby strengthen local finance.
London plans city of the future
Authors: Lanchester H. V.
Published: July 2007

Governmental authorities, professional and welfare groups cooperate to study traffic congestion and develop better housing, open spaces, ideal location of homer and industry.
Louisiana clings to reform
Authors: Gilmore Harlan W.
Published: July 2007

New administration under “Jimmie” Davis pledges itself to continue policies initiated by Governor Sam H. Jones; many unsolved problems offer challenge to new executive.
Researcher's digest: April
Authors: Roher Miriam
Published: July 2007

Units of government in Oregon; 15 years oj assessment problems; cost of golf in Schenectady war improvements in personnel practices; league of cities recognized.
Election frauds go unchecked
Authors: Lex William Barclay
Published: July 2007

Philadelphia politicians abandon old‐time violence in favor of chicanery; learn how to circumvent permanent registration with which reformers sought to thwart them.
On the local front
Authors: Franklin Zilpha C.
Published: July 2007

Prepared by the Office of Community War Servicee Federal Security Adminiatrator Pad V. McNutt, Director.
One man grand jury in action
Authors: Lovett William P.
Published: July 2007

Michigan's unique system of exposing wrongdoers wrings confessions of legislative corruption; citizen interest and action again start process of legal investigation.
Researcher's digest: June
Authors: Roher Miriam
Published: July 2007

Maxims by a researcher, Middletown and postwar planning, Illinois considers billboards, Indiand's representatives.
On the local front
Authors: Franklin Zilpha C.
Published: July 2007

Prepared by the Office of Community War Service Federal Security Administrator Paul V. McNutt, Director.
20 years forward in Cincinnati
Authors: Reed Thomas H. , Reed Doris D.
Published: July 2007

Authoritative evaluation reveals Ohio metropolis has benefited vastly from “revolution” against politics‐ridden machine; finds civic parsimony chief weakness.
How to set up utility districts
Authors: Bauer John
Published: July 2007

Operation by central city, with representation from rest of metropolitan area, beat method; weU planned regional organization provided by state a workable alternative.
The league and the future
Authors: Beard Charles A.
Published: July 2007

The responsibilities and opportunities of the League have not diminished; they are greater now than they ever have been in the course of the past 50 years.
The League's second stretch
Authors: Childs Richard S.
Published: July 2007

At the end of its first half century the League remains principal custodian of the problems which concern the practical relationships o f citizens to their governments.
Michigan attacks ‘red tape’
Authors: Ford Robert S.
Published: July 2007

Officials and Bureau of Business Administration develop plans to streamline and simplify government to eliminate evils of bureaucracy; see antedote for centralization.
Machine beats county charter
Authors: Willmott John F.
Published: July 2007

Vigoroua efforts to secure streamlined council‐manager plan for suburb of nation's capital loses to campaign of misrepresentation; Montgomery County citizens to try again.
The GI's cast their ballots
Authors: Lippert David J.
Published: July 2007

The mystery of the soldier vote is explained by a Gl himself who lets in the light and chases the hobgoblin that has haunted the dreams of the political alarmists.
Let's quarantine the bosses
Authors: Edison Charles
Published: July 2007

Former New Jersey Governor, foe of Hagueism, gives some sound suggertions for taking “the boss” out of politics.
The shame of the cities—1946
Authors: Gulick Luther
Published: July 2007

Not graft and corruption, not boss rule, but lasy citizens, lack of city pride, failure to plan termed principal failure.
County pattern for the future
Authors: Mauck Elwyn A.
Published: July 2007

Manager plan, budgeting, cooperation with communities and state, as well as civic leaderrhip, seen as essential.