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  • Springer  (48,496)
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  • National Academy of Sciences  (1,893)
  • 1985-1989  (95,370)
  • 1950-1954
  • 1985  (95,370)
  • 1
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    Bulletin of mathematical biology 47 (1985), S. 1-21 
    ISSN: 1522-9602
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    Notes: Abstract A general mechanism underlying bursting is proposed and described. It consists of two coupled nonlinear oscillators with different frequencies, where the slower oscillator alternatively switches the faster one on and off. This mechanism is shown to work in an extended Bonhoefer-van der Pol oscillator as well as in a modified version of the Hodgkin-Huxley equations.
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    Bulletin of mathematical biology 47 (1985), S. 145-153 
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    Notes: Abstract Pointwise upper and lower bounds for the solution of a class of nonlinear diffusion problems with Michaelis-Menten kinetics are presented. Simple analytical bounding curves are obtained and for an illustrative case the calculated values bound the recent numerical solution of P. Hiltmann and P. Lory, 1983.Bull. math. Biol. 45, 661–664.
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    Bulletin of mathematical biology 47 (1985), S. 337-342 
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    Notes: Abstract The cellular response in terms of steady-state variance of cell mass concentration to fluctuations in incoming nutrient concentration to a chemostat has been examined. A white noise process is assumed to describe incoming nutrient concentration fluctuations and the variance of cell mass concentration has been found to depend on cell yield (a lumped measure of nutrient concentration fluctuation magnitude and lifetime) and two system time constants.
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    Bulletin of mathematical biology 47 (1985), S. 343-365 
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    Notes: Abstract In a well-known collection of his essays in cognitive psychology Miller (The Psychology of Communication. Penguin, 1974) describes in detail a number of experiments aiming at a determination of the limits (if any) of the human brain in processing information. He concludes that the ‘channel capacity’ of human subjects does not exceed a few bits or that the number of categories of (one-dimensional) stimuli from which unambiguous judgment can be made are of the order of ‘seven plus or minus two’. This ‘magic number’ holds also, Miller found, for the number of random digits a person can correctly recall on a row and also the number of sentences that can be inserted inside a sentence in a natural language and still be read through without confusion. In this paper we propose a dynamical model of information processing by a self-organizing system which is based on the possible use of strange attractors as cognitive devices. It comes as an amusing surprise to find that such a model can, among other things, reproduce the ‘magic number seven plus-minus two’ and also its variance in a number of cases and provide a theoretical justification for them. This justification is based on the optimum length of a code which maximizes the dynamic storing capacity for the strings of digits constituting the set of external stimuli. This provides a mechanism for the fact that the ‘human channel’, which is so narrow and so noisy (of the order of just a few bits per second or a few bits per category) possesses the ability of squeezing or ‘compressing’ practically an unlimited number of bits per symbol—thereby giving rise to a phenomenal memory.
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    Bulletin of mathematical biology 47 (1985), S. 409-424 
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    Notes: Abstract Electrical polarization of an artery or an arteriole may be modeled by the use of equations developed for two-dimensional cable theory. Two special cases have previously been solved: those corresponding to the case in which the radius is either zero (one-dimensional cable theory) or infinite. This paper presents the general solution.
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    Bulletin of mathematical biology 47 (1985), S. 367-407 
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    Notes: Abstract The distance geometry approach for computing the tertiary structure of globular proteins emphasized in this series of papers (Goelet al., J. theor. Biol. 99, 705–757, 1982) is developed further. This development includes incorporation of some secondary structure information—the location of alpha helices in the primary sequence—in the algorithm to compute the tertiary structure of alpha helical globular proteins. An algorithm is developed which estimates the interresidue distances between chain-proximate helices. These distances, in conjunction with the global statistical average distances obtainable from a database of real proteins and determined by the primary sequence of the protein under study, are used to determine the tertiary structure. Five proteins, parvalbumin, hemerythrin, human hemoglobin, lamprey hemoglobin, and sperm whale myoglobin, are investigated. The root mean square (RMS) errors between the calculated structures and those determined by X-ray diffraction range from 4.78 to 7.56 Å. These RMSs are 0.21–2.76 Å lower than those estimated without the secondary structure information. Contact maps and three-dimensional backbone representations also show considerable improvements with the introduction of secondary structure information.
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Bulletin of mathematical biology 47 (1985), S. 425-434 
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    Notes: Abstract If a plane membrane consists of patches, each with a given area and a given diffusion coefficient, then the transient of the total unidirectional flux of a diffusing substance (as defined experimentally by Ussing) is predictable. Here the inverse problem is studied: given only the observed transient of the total unidirectional diffusion flux, the unknown membrane heterogeneity transverse to the flux is to be quantified. The ratio of the arithmetic and of the harmonic means (both area-weighted) of the diffusion coefficients, evaluated over the membrane, is expressed in terms of the observed transient alone and is used to characterize the heterogeneity. A unique exact solution of the inverse problem for two kinds of patches is obtained in closed form. A singular limit of this solution pertains to currently postulated models of endothelial membranes, for which a characteristically shaped transient is predicted.
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    Bulletin of mathematical biology 47 (1985), S. 435-435 
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    Bulletin of mathematical biology 47 (1985), S. 437-474 
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    Notes: Abstract Major types of sequence similarity searching (often, and incorrectly, called ‘homology’ searching) are reviewed and examples of each are presented. The features and limitations of each type of program, and individual implementations of each type are discussed. Two pairs of sequences are used as examples to show how implementations of each type differ in their results and their presentation. Both local and global alignment programs are examined, and the programs reviewed run on many different types of computer architectures, from laboratory computers such as the IBM PC, minicomputers such as the VAX, to large mainframe computers such as DEC-10/20 series.
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    Bulletin of mathematical biology 47 (1985), S. 489-494 
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    Notes: Abstract Criteria for the existence of globally stable equilibria in classical Volterra predator-prey systems represented by loop graphs are provided by comparing the community matrix with a matrix belonging to matrix classS W .
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    Bulletin of mathematical biology 47 (1985), S. 475-487 
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    Notes: Abstract Ordinary reaction-diffusion mechanisms do not account for size invariance properties of morphogenetic fields. We show that such a failure results from ignoring cell individuality. By considering purely topological factors, such as the number of intercellular contacts or the extent of the cell surface in contact with neighbouring cells, size invariance exists in reaction-diffusion systems. Our results are general, model independent and may be applied to any multi-unit ensemble exhibiting coherent behaviour.
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    Bulletin of mathematical biology 47 (1985), S. 495-502 
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    Notes: Abstract The artery is treated as a thick-walled cylindrical shell. Using the large deformation theory, an analytical expression for the pulse wave speed is obtained and the effect of twist on the wave speed is discussed. Numerical results indicate that although phase velocity increases with pressure, it decreases with increasing twist angle.
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    Bulletin of mathematical biology 47 (1985), S. 545-550 
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    Notes: Abstract The effect of the shape of stenosis on the resistance to blood flow through an artery with mild local narrowing has been studied. It is shown that the resistance to flow decreases as the shape of stenosis changes and the maximum resistance is attained in the case of symmetric stenosis.
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    Bulletin of mathematical biology 47 (1985), S. 535-543 
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    Notes: Abstract A set of 2n−2 relations (edges) and a set ofn−1 hypothetical taxonomic units (HTUs) derive from the estimation of a binary phylogeny of a set ofn operational taxonomic units (OTUs). We propose an easy way for numbering thesen−1 hypothetical taxonomic units, as well as for then−2 interior points of an unrooted binary phylogeny. We also present an alternative method to the one proposed by Rohlf (Bull. math. Biol. 45, 33–40, 1983) for numbering the π i=1 n (2i−3) possible rooted binary phylogenies and the π i=1 n−1 (2i−3) possible unrooted binary phylogenies conerning a set ofn operational taxonomic units. An illustrative example of the method is presented. It is hoped that some studies in phylogenetics will become more accessible, from the viewpoint of computational economy, by the use of this method.
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    Bulletin of mathematical biology 47 (1985), S. 503-512 
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    Notes: Abstract The heterogeneity of rat brain opiate receptors was examined by analyzing competition data. The binding of three prototypical tritiated opioid agonists, [3H]-dihydromorphine ([3H]-DHM), [3H]-D-ala2-D-leu5-enkephalin ([3H]-DADLE), and [3H]-ethylketocyclazocine ([3H]-EKC) was determined in the presence of varying concentrations of each of these unlabeled ligands, generating nine displacement curves. A computer program was then used to find the best fit of a model system to these data, assuming two, three or four independent binding sites. The best fit was a four-site model. One of these sites is specific for DHM; two are relatively selective for DHM and DADLE respectively, but also bind EKC. The remaining site binds only EKC with high affinity. These results, together with displacement data using naloxone, FK33824, and D-ala2-met5-enkephalinamide, are discussed in terms of current opiate receptor models.
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    Bulletin of mathematical biology 47 (1985), S. 651-668 
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    Notes: Abstract This work continues with an examination of capillary exchange models as operators, namely the operatorsO k andK αk relating extravascular and intravascular concentration to input for the Krogh cylinder model of a single capillary, a model basic to many organ models. Fundamental algebraic and analytic properties are presented: the operators belong to a commutative Banach algebra; an addition theorem holdsK αk +K βk =K α+β,k ; the operatorK αk has an inverse;K αk -1 , (as an operator on LebesgueL p space or on the locally integrable functions); partial derivatives are given forK αk [f](t) andO k [f](t) (sensitivity functions); and inequalities are established for the derivatives. Dominance relations between model curves are inferred. Error bound formulas are presented forK andO as bounds on ‖K αk f-K βl f‖ p and ‖O k f-O l f‖ p for allL p . Consequent limitations on relative errors are shown. The implications for operators on a finite time interval are deduced.
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    Bulletin of mathematical biology 47 (1985), S. 669-683 
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    Notes: Abstract The nonlinear nature of the hydraulic permeability, as well as the corresponding pressure and displacement fields, in a soft tissue are studied for steady-state permeation. From a two-phase continuum model analytical expressions are derived that can be used with the results from a permeation experiment to determine the dependence of the permeability on the strain. In the process it is found that, because of the compaction of the tissue arising from fluid flow, it is necessary to distinguish between the apparent and intrinsic permeability. The former, which is an averaged quantity, is the permeability usually obtained in permeation studies. However, as shown from the analysis, it can differ substantially from the latter, which is the local permeability in the tissue.
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Bulletin of mathematical biology 47 (1985), S. 695-695 
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    Bulletin of mathematical biology 47 (1985), S. 697-738 
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    Notes: Abstract The analytic, eccentric spheres model of the torso was used to examine the validity of approximating the ‘infinite medium’ potential by integrating ‘finite medium potentials’ over the torso surface. Although idealized, the analytic model is sophisticated enough for all important torso conductivity and geometry parameters to be preserved in the formulation. The model generates both ‘finite medium’ potentials (for which the torso is surrounded by air) and also ‘infinite medium’ potentials (for which the outermost layer of the torso extends outward to infinity). The finite medium torso potentials were integrated over the torso surface in accordance with the approximation used by many investigators in an effort to make the surface distribution more representative of the primary cardiac sources. The resulting potential distribution was compared with the true infinite medium potential, in which the effects of internal inhomogeneities (secondary sources) were taken into account. The difference between the two representations was found to be significant, and caution should be used when interpreting such data.
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    Bulletin of mathematical biology 47 (1985), S. 739-748 
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    Notes: Abstract Environ analysis, an input-output analysis for models of ecological systems, has been previously formulated for linear systems. This note has a twofold purpose: first, we indicate that a variation of parameters technique can be applied, at least in principle, to computeboth input and output environs; and second, we show that this technique may be used for computation of environs in nonautonomous, nonlinear compartment models. This nonlinear theory, obtained as a direct extension of dynamical system developments, allows the traditional environ partitioning of compartmental storages and flows. An example of a nonlinear nutrient-producer-consumer system whose output environs can be computed asymptotically is presented to illustrate these concepts.
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    Bulletin of mathematical biology 47 (1985), S. 749-755 
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    Notes: Abstract Prolonged exposure to cyanide leads to a delayed but reversible disappearance of tetanic hyperpolarization in theXenopus node (G. M. Schoepfle,Am. J. Physiol. 231, 1033–1038, 1976). This effect is attributed to a pronounced decline in the absolute values of the ATP and ADP concentrations, such that the ATP-driven ion translocation is no longer possible, regardless of the existing values for (Na)i, (K)i and the (ATP)/(ADP) ratio. Mathematically, this would imply a vanishing of a constant pump conductance gp in the exression for electrogenic pump current densitityJ p, whereJ p=g p (V m −E p) in whichV m is membrane potential andE p is an ATP-and sodium-dependent e.m.f.
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    Bulletin of mathematical biology 47 (1985), S. 757-764 
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    Notes: Abstract For the two-parameter (A, α) exponentially-stiffening constituitive relation, typical of many biological materials, it is shown that the uniaxial stress-strain behavior of an initially curved strip is significantly changed by the residual bending stresses. Closedform theoretical results depend on the thickness to radius ratio (h/R) and the relative strain level ε(h/R). The bending stresses tend to obscure accurate measurement ofA and α unless care is taken. However, it is shown that by changing co-ordinates to (dℝ/d∈, ℝ)-space, bothA and α can be recovered from the high stress data, and α alone can be recovered from the low stress data. This has practical application to the mechanics of cornea, sclera, and heart muscle.
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    Bulletin of mathematical biology 47 (1985), S. 765-769 
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    Notes: Abstract An axisymmetric flow of a power law fluid through circular tubes under constant pressure gradient with the flow parameters varying radially is analyzed theoretically. The main finding is that for the Fahraeus-Lindqvist (F-L) effect to occur, it is necessary to have at least one of the parametersK (consistency) andn (index) as a discontinuous function ofr in the absence of wall slip; and with slip condition the parameters could be continuous functions ofr under specific conditions. In both the cases the existence of more than one discontinuity cannot be ruled out. The results obtained are consistent with experimental findings of blood flow through narrow tubes.
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    Bulletin of mathematical biology 47 (1985), S. 771-782 
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    Notes: Abstract This is a study of the properties of a zygotic algebra of two linked autosomal loci with different recombination rates in males and females, without selection or mutation and with random mating. The above-mentioned zygotic algebra contains a genetic subalgebra. A canonical basis of this subalgebra is constructed and the train roots are calculated.
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    Bulletin of mathematical biology 47 (1985), S. 799-799 
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    Bulletin of mathematical biology 47 (1985), S. 783-789 
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    Notes: Abstract Among the conformations which the DNA molecule can adopt, the transition beween the A and B families, controlled by water content (relative humidity), seems to be implicated in the transcription process. Focusing on the main structural difference involved (tilting of base normals with respect to the helix axis), a model is constructed, solitary wave solutions of the resulting equation of motion are demonstrated and possible experimental implications indicated.
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    Bulletin of mathematical biology 47 (1985), S. 791-797 
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    Notes: Abstract Balls are removed one-at-a-time at equal time intervals from an urn initially containingw 0 white balls and a large number b of black balls and each black or white ball is immediately replaced by a black ball. The distribution of the number of white balls remaining aftert iterations (under certain limiting operations) is taken from the literature. The problem is to use this result to find the time required to remove a fixed number of white ballsw 1 from the urn. We then find the mean and variance of this distribution and also look at the special case whenw 1 =w 0.
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Circuits, systems and signal processing 4 (1985), S. 285-300 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Magnetostatic surface wave (MSSW) devices made with pure and gallium-substituted yttrium-iron garnet (Ga:La-YIG) films are described. These devices include nondispersive and dispersive delay lines, band-pass filters, oscillators, and resonators. By controlling the magnitude of the bias magnetic field and the temperature of operation, it is possible to tune these devices over a wide frequency range extending from 0.3 to 4 GHz and from 3 to 18 GHz using Ga:La-YIG and pure YIG films, respectively. These devices could be used in pulse compression radar, microscan receivers, complicated Fourier transform processors, and fundamental oscillator circuits. In this paper, we briefly show results for pure YIG devices tunable in C and X bands and discuss, in detail, the performance of the Ga:La-YIG devices for UHF applications.
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    Circuits, systems and signal processing 4 (1985), S. 301-316 
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    Notes: Conclusion Significant improvements are required in the performance of MSW dispersive delay lines and filter banks before they are ready for systems application. Typically delay lines with bandwidths of 1 GHz or greater, differential delays in the range 200 ns to 1μs, and minimum phase errors (〈±1 °) are required for large (∿40 dB) dynamic range compressive receivers. However, techniques are evolving (see rest of this issue) in this relatively new area of technology which will allow systems performance requirements on phase errors to be met. Possible approaches to low phase error dispersive delay lines include reflective arrays, stepped ground planes, and multiple YIG films. The stepped ground plane technique is the most advanced and uses an optimization approach to the delay-line design, which results in a minimum phase error [20]. Ultimately the minimum achievable phase error will be limited by reflections from transducers and multiple mode effects in the delay lines. The MSW compressive receiver requires parallel advances in high-speed digital processing techniques to achieve its full potential. The MSW filter bank provides a simple channelization technique applicable up to approximately 20 GHz. Narrowband channels with 10 dB insertion loss, 3 dB bandwidths of 10 to 40 MHz, and 50 dB bandwidths of 30 to 120 MHz are possible with the already demonstrated techniques. Broader bandwidth channels in the range 50 to 200 MHz with flat passband response require improved transducer design techniques. The channelized receiver does not require extremely high-speed operations but, since a large number of channels are involved, size and cost become very significant.
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    Circuits, systems and signal processing 4 (1985), S. 413-434 
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    Notes: Abstract In recent studies, it has been verifiedheuristically andexperimentally (via simulations) that instability in power systems due to a fault occurs when one machine or a group of machines, called thecritical group, loses synchronism with the remaining machines. Using energy functions associated with a critical group (rather than system-wide functions), transient stability results which are less conservative than other existing results, have been obtained. The existence and identity of a critical group is ascertained in these studies byoff-line simulations. In this paper, we present results, for power systems with uniform damping, which establishanalytically theexistence and theidentity of the critical group of machines due to a given fault. We also present a result to determine estimates of the domain of attraction of asymptotically stable equilibrium points in power systems. The results presented herein can potentially be usedon-line to determine which machines belong to a critical group, and to use this information for corrective action (e.g.,shedding of the critical generators orfast valving for these generators). The applicability of the present results is demonstrated by means of a specific example (a 162-bus, 17-generator model of the power network of the State of Iowa).
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    Circuits, systems and signal processing 4 (1985), S. 367-383 
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    Notes: Abstract In a previous paper [1], a new algorithm for ARMA spectral estimation of stationary time series has been presented. The algorithm is based on nonlinear least squares fit of the sample partial autocorrelations to the partial autocorrelations generated by the assumed ARMA model. This paper explores the statistical properties of the above algorithm, including some numerical examples of the asymptotic variance of the estimated parameters, as compared to the Cramer-Rao bound. The results confirm the good performance of the algorithm and suggest an improvement in its implementation.
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    Circuits, systems and signal processing 4 (1985), S. 335-350 
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    Notes: Abstract A potential application of MSW technology lies in the area of time delay for future low-sidelobe wide-bandwidth phased array antennas. High-precision MSW electronically tunable analog time-delay units in transmit/receive modules in phased arrays have the potential of greatly enhancing antenna system capabilities, by increasing instantaneous operating bandwidth and decreasing sidelobe levels, over phased array systems using only phase shifters or switched lines for beam steering and control. This paper provides a status report of MSW time delays for such arrays.
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    Bulletin of mathematical biology 47 (1985), S. 35-52 
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    Notes: Abstract The present study deals with the effect of externally-imposed body accelerations on blood flow in arteries. Body accelerations may be caused deliberately, for example making the subjecs lie down on vibrating tables: or unintentionally during travel in road vehicles, aircraft or spacecraft. A mathematical model of flow in single arteries subject to a pulsating pressure gradient as well as body acceleration is presented. The resulting equations are solved by using the technique of Laplace transforms. Computational results are presented for the effects of body accelerations on flow variables namely flow rate, velocity of flow, acceleration and shear stress corresponding to typical arteries of human subjects.
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    Bulletin of mathematical biology 47 (1985), S. 53-70 
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    Notes: Abstract The left ventricle is modelled as a prolate spheroid of viscoelastic material with an aim to demonstrate the qualitative effects of anistropy and nonhomogeneity in the calculation of intact ventricular wall stresses. The pericardial pressure is accounted for in the analysis and an attempt is made to examine to what extent this influences the ventricular stresses. Numerical results are also obtained by computing the analytical expressions derived through the analysis.
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    Bulletin of mathematical biology 47 (1985), S. 111-122 
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    Notes: Abstract A Montes Carlo computer simulation is designed in order to described the evolution of an ecosystem under imposed environmental conditions of energy. Some preliminary results of a simple situation show a suggestive matching between the detailed random behaviors of individuals and a global deterministic model. This fact may provide a new insight into the understanding and control of biomass production processes and represents a new tool for the evaluation of the reliability of the classical treatments.
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    Bulletin of mathematical biology 47 (1985), S. 71-110 
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    Notes: Abstract A commonly accepted mathematical model for the slow-wave electrical activity of the gastro-intestinal tract of humans and animals comprises a set of interconnected nonlinear oscillators. Using a van der Pol oscillator with third-power conductance characteristics as the unit oscillator a number of structures have been analysed using a matrix Krylov-Bogolioubov method linearisation. The mode analysis of one-dimensional chains and two-dimensional arrays has been reported. In this paper the method has been extended to consider a tubular structure which is relevant to modelling small-intestinal rhythms. It is shown that this structure is capable of producing stable single models, non-resonant double modes and degenerated modes. General expressions are obtained for anm×n structure and examples given of two special conditions of 3×4 (i.e. odd numbers of oscillators in a ring) and 4×3 cases. The analytical results obtained for these two cases have been vertified experimentally using an electronic implementation of coupled van der Pol oscillators. Results obtained using fifth-power non-linear oscillators are summarised.
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    Bulletin of mathematical biology 47 (1985), S. 157-157 
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    Bulletin of mathematical biology 47 (1985), S. 161-192 
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    Bulletin of mathematical biology 47 (1985), S. 159-159 
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    Bulletin of mathematical biology 47 (1985), S. 205-213 
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    Notes: Abstract An urn contains balls ofs different colors. The problem of the reinforcement of a specified color and random depletion of balls has been considered by Shenton (1981, 1983). In this paper, the theory is applied to the biological age dependent half-life of radioactive iodine in man; the data of Cook and Snyder (1965) is used. The intake of radioactive iodine and its retention subsequently is studied.
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    Bulletin of mathematical biology 47 (1985), S. 193-204 
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    Notes: Abstract One of the limitations of stochastic, linear compartmental systems is the small degree of variability in the contents of compartments. S. R. Bernard's (1981) urn model (S. R. Bernardet al., Bull. math. Biol. 43, 33–45.) which allows for bulk arrivals and departures from a one-compartment system, was suggested as a way of increasing content variability. In this paper, we show how the probability distribution of the contents of an urn model may be simply derived by studying an appropriate set of exchangeable random variables. In addition, we show how further increases in variability may be modeled by allowing the size of arrivals and departures to be random.
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    Bulletin of mathematical biology 47 (1985), S. 231-238 
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    Notes: Abstract A stochastic model based on Eigen and Schuster's theory of biomolecular self-replication is studied by treating the master equation with the system-size expansion technique. The steady-state results are found to be in good agreement with the previous results and with those derived from the principle of detailed balancing. Multispecies competition and coexistence are studied carefully with the conclusions that a stable steady state is predicted for the former and a metastable state for the latter. The stochastic selection processes are also analyzed and discussed.
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    Bulletin of mathematical biology 47 (1985), S. 215-229 
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    Notes: Abstract A consensus in dex method comprises a consensus method and a consensus index that are defined on a common set of objects (e.g. classifications). For each profile of objects, the consensus method returns a consensus object representing information or structure shared among profile objects, while the consensus index returns a quantitative measure of agreement among profile objects. Since the relationship between consensus method and consensus index is poorly understood, we propose simple axioms prescribing it in the most general terms. Many taxonomic consensus index methods violate these axioms because their consensus indices measure consensus object invariants rather than profile agreement. We propose paradigms to obtain consensus index methods that measure agreement and satisfy the axioms. These paradigms salvage concepts underlying consensus index methods violating the axioms.
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    Bulletin of mathematical biology 47 (1985), S. 239-262 
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    Notes: Abstract The theory of multitype branching processes is applied to the kinetics of polynucleotide replication. The results obtained are compared with the solutions of the deterministic differential equations of conventional chemical kinetics.
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    Bulletin of mathematical biology 47 (1985), S. 263-272 
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    Notes: Abstract We investigate the circumstances under which the moments of the order statistics of the extinction times of a set of independent branching processes exist. This extends a result of Schuster and Sigmund,Bull. math. Biol. 46, 11–17, 1984, which was found in a special random selection model. Furthermore we discussed existence of the expectation of extinction times of multitype branching processes and extend well known results for irreducible processes to the reducible case.
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    Bulletin of mathematical biology 47 (1985), S. 287-293 
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    Notes: Abstract This note presents a general time-dependent study of linear stochastic compartmental models in discrete time. The transient distribution of the state of the system is obtained by adapting methods used in the continuous time analysis. Covariance functions with and without a time lag are then deduced by a simple probabilistic argument. Results are derived in the Markov case and are partly extended to the semi-Markov case.
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    Bulletin of mathematical biology 47 (1985), S. 273-286 
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    Notes: Abstract A simple practical method exists for classifying and comparing planar curves composed of connected line segments. This method assigns, a single numberD, the fractal dimension, to each curve.D=log(n)/[log(n)+log(d/L)], where:n is the number of line segments,L is the total length of the line segments, andd is the planar diameter of the curve (the greatest distance between any two endpoints). At one end of the spectrum, for straight line curves,D=1; at the other end of the spectrum, for random walk curves,D→2. Standard statistics are done on the logarithms of the fractal dimension [log(D)]. With this measure, trails of biological movement, such as the growth paths of the cells and the paths of wandering organisms, can be analyzed to determine the likelihood that these trails are random walks and also to compare the straightness of the trails before and after experimental interventions.
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    Bulletin of mathematical biology 47 (1985), S. 295-304 
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    Notes: Abstract A model is proposed of an ecological community where some (or all) of the subpopulations exhibit mutual interference. Mutual interference introduces sublinearities which makes the persistence analysis of the community more complex since the model is no longer a dynamical system. A transformation is introduced which yields a dynamical system, thereby making a persistence analysis more tractable. The results are applied to determining top-predator persistence of a simple food chain and to the question of invasibility of a stable community by a new subpopulation.
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    Bulletin of mathematical biology 47 (1985), S. 613-627 
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    Notes: Abstract This paper concerns the fluid-mechanical study of the effects of permeability of the wall of an arteriosclerotic blood vessel by idealizing the tissue space as a porous medium bounding the blood vessel and the arteriosclerotic blood vessel as a constricted axisymetric tube of slowly but arbitrarily varying cross-secton. An analytical solution in the general case is obtained by perturbation technique and several important particular geometries of constriction are discussed as special cases. Numerical results for the effects of permeability on the wall shear stress and filtration velocity are shown graphically.
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    Bulletin of mathematical biology 47 (1985), S. 629-650 
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    Notes: Abstract Beginning from the notion of semantic network structure, we develop a quantitative description of how much can be learned by an animal whose developmental programme is a set of co-acting epigenetic rules. In the model considered, the activity of the rules regulates the size, connectivity and innate information content of the semantic network. The network itself is associated with a behavioral repertoire. The modeling approach shows how to begin accounting for the effects of both genetic and environmental information, in a manner that quantifies the roles of specific epigenetic rules for psychological development. In previous models the Shannon-Weaver information contentI of a semantic network follows power lawsI ∞N ξ, withN the number of interrelated concept elements in the network and ξ a scaling exponent labeling a universality class of semantic networks. Our calculations provide evidence that epigenetic rules of the type considered, involving both innate and learned semantic network components, sustain a new universality class for which ξ=1.
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    Circuits, systems and signal processing 4 (1985), S. 41-62 
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    Notes: Abstract This is a review of two electrical equivalent circuits for multi-element magnetostatic wave transducers. The two circuit models are identified as a transmission line and a two terminal model. Both models have been extended to all three principal MSW modes of propagation to the point where computer programs have been written to plot phase and amplitude response as measured by commercial network analyzers. A review is provided of the basic assumptions, similarities and differences, advantages and disadvantages, and limitations of the two models. The useful range of them covers many cases of practical interest in the one to twelve Ghz frequency range.
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    Circuits, systems and signal processing 4 (1985), S. 201-209 
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    Notes: Abstract The performance of the magnetostatic surface wave straight-edge resonator (MSSW-SER) is presented. The resonator uses a rectangular YIG film to propagate MSSWs where the straight edge serves as a reflector. Problems arising from coupling to width mode resonances and their effect on the main resonance are investigated. Through a careful choice of YIG and transducer parameters, the interference effects of the width mode resonances with the main resonance are minimized. As a result, highQ tunable microwave resonators with a tuning range from 2–20 GHz, insertion loss less than 10 dB, and spurious rejection better than 10 dB could be designed and fabricated. This MSSW resonator could be used to construct a tunable low-phase-noise feedback oscillator. However, the tuning range of this MSW feedback oscillator is limited by the phase change of the external amplifier circuit.
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    Circuits, systems and signal processing 4 (1985), S. 89-103 
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    Notes: Abstract This paper presents in a condensed form, a review of information regarding the technology of yttrium iron garnet (Y3Fe5O12 — YIG) film growth for MSW applications. The method used for film growth is liquid phase epitaxy from a molten solution of PbO/B2O3 into which Y2O3 and Fe2O3 have been added. There are five sections to the paper. The first is an introduction to the crystalline and magnetic features found in YIG. A short second section deals with growth techniques and apparatus. In a third section the melt composition, conditions of growth and homogeneity of as grown material are explored. Growth temperatures varying from 848° C to 998° C have been shown to successfully produce YIG films. Possible sources of MSW loss are explored in the fourth section. It is seen that material contamination and physical irregularities may have a negative effect onΔH. The final section summarizes the state in which YIG film production now stands. The finding is that although usable films are producible routinely, intrinsic performance is not yet achievable on a regular basis.
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    Circuits, systems and signal processing 4 (1985), S. 5-7 
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    Circuits, systems and signal processing 4 (1985), S. 115-135 
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    Notes: Abstract Magnetostatic waves are intrinsically suited for use in microwave dispersive delay lines, because they are readily generated at high frequencies and their velocity is frequency dependent. Here we review progress toward meeting the systems requirement that the delay time be linear in frequency. Magnetostatic waves can approach this condition if a ground plane is nearby or if two or more ferrite layers are present; with forward volume waves one may also use a dispersive reflecting array, as is done with surface acoustic waves. The use of a properly shaped ground plane gives the lowest phase errors so far measured (±16° over 0.6 GHz); multiple ferrite layers show promise of allowing the greatest delay.
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    Circuits, systems and signal processing 4 (1985), S. 221-225 
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    Notes: Abstract A theoretical derivation of theQ-factor of an MSW delay-line based oscillator is presented which is based on a rigorous, classical definition of theQ-factor of a resonator. The theory takes into account (1) the propagation loss in the delay line, (2) the transduction losses at the input and output transducers of the delay line, (3) the delay times in the delay line and the circuit external to the delay line, and (4) the loading of the oscillator. While the present work was done with MSW in mind, the results are generally applicable to all delay-line based oscillators and would, for instance, apply to the SAW delay-line based oscillators.
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    Circuits, systems and signal processing 4 (1985), S. 253-263 
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    Notes: Abstract The present paper reviews recent theoretical results, and reports initial experimental results, on the convolution of contra-propagating magnetostatic forward volume waves (MSFVWs), in the form of cw signals or time-limited cw pulses, in an epitaxial yttrium iron garnet (YIG) film. Computations of the convolver bilinearity factorF int indicate an efficient convolution process over a wide bandwidth, with values ofF int that are of the same order as, or better than, the reported experimental results for MSW convolution in a YIG cylindrical or plate geometry. The values of Fint determined experimentally are in excellent agreement with theory. These results are of interest to microwave system developers particularly if bandwidths of 1 GHz or larger can be realized in practice. A limiting feature of magnetostatic wave (MSW) convolvers is that the maximum delay time of a delay line that is realizable without excessive insertion loss is in the order of 0.5μs. The advantage of MSW convolvers, of course, lies in their ability to perform signal processing directly at microwave frequencies, and in applications such as electronic warfare the advantageously large bandwidths would mitigate the limitations in delay time.
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    Circuits, systems and signal processing 4 (1985), S. 439-457 
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    Notes: Abstract We set out a procedure for defining the region of wavenumber support relevant for maximum entropy spectral estimation of a noise field incident on a planar array. We consider first linear, nonequispaced arrays, and argue that the problem of defining a region of wavenumber support is only well-posed when either position uncertainty for the array elements is postulated, or phase uncertainty in the measurement of the signals at the array elements is postulated, or one acknowledges that a polar diagram that is almost periodic defines an aliasing frequency in virtually the same way as a polar diagram which is periodic. For planar arrays, the region of wavenumber support can be approximately circular but in general has to be defined with reference to the particular array.
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    Circuits, systems and signal processing 4 (1985), S. 485-502 
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    Notes: Abstract This paper investigates the zero-input stability properties of the exact second-order recursive digital filter having both overflow and quantization non-linearities. Two examples demonstrate the adverse influence of quantization on the overflow-stability property of the filter. Three sets of conditions are presented to ensure asymptotic overflow-stability in the presence of quantization. Using these criteria, various regions in the coefficient plane corresponding to different minimum internal wordlengths required to ensure the non-interaction of overflow and quantization are derived. These results thus form a useful design criterion.
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    Bulletin of mathematical biology 47 (1985), S. 23-34 
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    Notes: Abstract An earlier paper by E. L. Keller, 1980,Bull. math. Biol. 42, 181–189, gave necessary and sufficient conditions for primitivity of a product of two Leslie matrices. This paper generalized that result to an arbitrary number of Leslie matrices. The generalized result shows that Keller's is, from one viewpoint, more conveniently stated in a slightly different form (our equation (6)). This restatement in turn simplifies the proof of his special case of the general result. It also shows that the case of products of just pairs of matrices is a special one in that the simple form of result obtained for that case doesnot retain its simplicity when generalized to higher order products.
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    Bulletin of mathematical biology 47 (1985), S. 155-155 
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    Bulletin of mathematical biology 47 (1985), S. 123-143 
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    Notes: Abstract A theoretical analysis of electric and magnetic fields of the heart, based solely upon the scalar multipole expansion, is carried out in order to gain an insight into the interrelation of the data contained in electro- and magnetocardiological measurements. The usual multipole expansion is applied for the electric field, however corresp[nding equivalent multipoles are formulated as idealized generators, having not only flow sources, but also vortex sources of the field. Furthermore, the magnetic field in a homogeneous infinite volume conductor is expressed as a sum of two series, the first being the usual multipole expansion of the nonvortex component of the magnetic field, and the second being a sequence of magnetic fields set up by the aforementioned electric multipole generators reduced to axial form. The former term is uniquely defined by the electric multipole components, but the latter reflects properties of the cardiogenerator that can be revealed only by means of magnetic measurements. Features of the electric and magnetic multipole components as integral characteristics of the cardiogenerator are discussed and concepts of the magnetic centre and magnetic axis of the cardiogenerator are proposed. The analysis is illustrated by examples of simple generator configurations.
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Bulletin of mathematical biology 47 (1985), S. 305-316 
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    Notes: Abstract The occurrence of multifurcations in essentially binary trees is investigated with respect to two methods for testing growth models,viz. subtree partition analysis and vertex analysis. It is shown that under certain conditions multifurcations may be incorporated in the analysis. Although the conditions are more restrictive for subtree partition analysis only minor loss of information occurs if forbidden multifurcations are simply ignored.
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    Bulletin of mathematical biology 47 (1985), S. 317-320 
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    Notes: Abstract An equation with five exponential terms is shown to fit the depolarized potassium current with different initial conditions. This equation has a molecular basis and was derived from the assumption that the potassium ions are transported under the combined forces via Newton's second law. It points out that the initial phase of the potassium current may take a different form and the usual concept that potassium conductance has a time delay may be misleading.
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    Bulletin of mathematical biology 47 (1985), S. 321-321 
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Bulletin of mathematical biology 47 (1985), S. 323-336 
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    Notes: Abstract A growth model for topological trees is formulated as a generalization of the terminal and segmental growth model. For this parameterized growth model, expressions are derived for the partition probabilities (probabilities of subtree pairs of certain degrees). The probabilities of complete trees are easily derived from these partition probabilities.
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    Bulletin of mathematical biology 47 (1985), S. 513-533 
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    Notes: Abstract We consider a Markov chain modeling competition between two alleles in a haploid population of constant size and undergoing mutation, selection and Fisher-Wright mating. The Markov chain is rescaled to a diffusion process. We study the interaction of external noise (due to a random selection coefficient) and internal fluctuations (due to mating); the interaction is found to be additive. The stationary probability density displays a critical point. We draw an analogy between the behavior of the probability density at the critical point and the theory of phase transitions; critical exponents are introduced and calculated. We also analyze the effect of external noise on the genetic diversity of the population and on mean first passage times of the gene frequency.
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    Bulletin of mathematical biology 47 (1985), S. I 
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    Bulletin of mathematical biology 47 (1985), S. 551-564 
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    Notes: Abstract This paper introduces a double-layer enzyme-membrane model representing the Na+−K+ pump in living cells. We present a mathematical solution to the problem of controlling the sodium flux in malignant cells, where an inhibitor exists in the outer layer of the membrane. We give an algorithm for the numerical resolution of this problem of optimal control with illustrations. Finally, we point out the biological importance of this study.
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    Bulletin of mathematical biology 47 (1985), S. 565-589 
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    Notes: Abstract In order to determine the growth of inhaled aerosol particles in the human respiratory tract the relative humidity in a lung model has been calculated using a numerical method. The computations take into account different types of airflows, enhanced transport mechanisms and an optimized wall temperature profile in the upper airways. These parameters are varied to fit experimental temperature data. Under certain conditions the corresponding relative humidity shows a maximum near the first bifurcation, which exceeds the final humidity in the alveoli. This high humidity forces dry NaC1 particles with diameters less than 0.5 μm to grow to their maximum size in the first bronchi. Thereafter the droplets loose water and reach their final size in the terminal bronchioles.
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    Bulletin of mathematical biology 47 (1985), S. 591-612 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We consider a class of differentiable dynamical systems that fulfill a criterion of adaptation, or beingfit. The adaptation criterion is found to be sufficient for the existence of hierarchical behavior in these systems, once they become complex. Commutative diagram methods are used to show that under reasonable conditions the hierarchical behavior takes the form of a closed dynamics of aggregate variables. This dynamics characterizes the system functions as a whole. Existence conditions for the aggregate dynamics are obtained, together with their differential form and their connections to the original system description. The results indicate that evolutionary processes are likely to produce systems that are hierarchically organized in term of their function as well as their structure.
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    Circuits, systems and signal processing 4 (1985), S. 3-3 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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    Circuits, systems and signal processing 4 (1985), S. 63-88 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Although magnetostatic wave devices normally employ spatially uniform magnetic bias, control of important features of the modes is afforded through judicious use of dc field gradients. Such control can be the basis for new forms of microwave signal processors. Gradients in either the field magnitude, direction, or both can be employed to affect wave dispersion or mode spectra. This is done to control prespecified characteristics such as frequency, rf energy distribution, impedance, and the velocity of energy propagation. Very general mathematical analyses of both the forward volume wave and surface wave geometries are developed for cases where the effective magnetic bias has, depending upon the mode, transverse spatial variation along either the ferrite film width or thickness caused by the applied field, saturation magnetization, magnetic anisotropy — or some combination. Computer simulation has been used to obtain eigenfrequencies and eigenmodes when the bias is uniform or nonuniform. The latter cases reveal that a great deal of control over the mode energy distributions can be exercised by the proper choice of gradients. For example, a forward volume wave can be forced to have strong field-displacement characteristics that are either nearly reciprocal or very strongly nonreciprocal.
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    Circuits, systems and signal processing 4 (1985), S. 157-180 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The continual demand for increased performance in modern communication and radar systems in terms of increased bandwidths and higher operating frequencies has led to investigation of novel techniques and technologies for analog signal processing. In particular, surface acoustic waves (SAW) have been extensively exploited with great success to this end, but systems requiring bandwidths greater than 500 MHz and center frequencies greater than 1 GHz have pushed SAW devices near the practical physical limit of the technology. A novel technology promising increased bandwidths at higher frequencies is based on magnetostatic waves (MSW) propagating in epitaxial films such as Yttrium Iron Garnet (YIG). These waves can be exploited in devices offering instantaneous bandwidths up to 2.2 GHz at microwave center frequencies from 0.5 to 20 GHz. MSW signal processing technology, based on transversal filtering concepts has been under extensive investigation for the past 10 years. This paper reviews the work that has been done utilizing the MSW technology in conjunction with reflective arrays to achieve practical spectral amplitude and delay modification.
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    Circuits, systems and signal processing 4 (1985), S. 181-200 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The purpose of this paper is to describe the current status of magnetostatic wave tunable resonators operating between 2 and 12GHz and their applications to microwave oscillators, the wave propagating in a pure yttrium-iron-garnet epi-layer. The first section deals with magnetostatic surface wave (MSSW) resonators consisting of a pair of reflective grooved gratings and two microstrip-transducers set between the gratings. Results on insertion loss, off-resonance frequency rejection andQ value are presented. However MSSW cavities suffer several disadvantages such as the small saturation power level at low frequencies and the difficulty to temperature compensate MSSW devices. These problems are overcome with magnetostatic forward volume waves (MSFVW). Then the second section is devoted to MSFVW resonators. A peculiar folded geometry made of five grooved gratings and two microstrip-transducers has been designed to provide a sufficient out-of-band rejection. The experimental characteristics of these resonators are given. In the last section of this paper are reported the features of tunable oscillators implemented with MSSW and MSFVW resonators in a hybrid configuration. Results about tunability, output power,FM phase noise are reported. MSFVW resonator stabilized oscillators are very promising and magnetostatic wave resonators seem a challenge to YIG spheres.
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    Circuits, systems and signal processing 4 (1985), S. 227-252 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The signal-processing characteristics of signal-to-noise enhancers and frequency-selective limiters are described. Performance of several practical devices is discussed. The theory of below-threshold operation is reviewed. New theoretical results are presented for calculation of threshold power and above-threshold power loss. Frequency selectivity and the consequences of linear losses are calculated for the limiter.
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    Circuits, systems and signal processing 4 (1985), S. 385-411 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper extends the problem of double-port matching of two frequencydependent non-Foster positive real impedances to that of multi-port matching. Givenn non-Foster positive real impedances and the preassigned transducer power-gain characteristics, necessary and sufficient conditions are given for the existence of a lossless, reciprocaln-port equalizer terminated in these impedances at the ports satisfying the prescribed transducer power-gain characteristics.
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    Circuits, systems and signal processing 4 (1985), S. 459-483 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A design method for two-dimensional (2-D) half-plane recursive digital filters is proposed. Constraints in the parameters of the designed transfer function are imposed to ensure octagonal symmetry in the magnitude response. Optimization algorithms are used to minimize thel p norm. The stability of these filters is checked easily by evaluating a small number of predetermined inequalities. Twelve designs are presented to show the characteristics and efficiency of the method proposed.
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    Circuits, systems and signal processing 4 (1985), S. 105-113 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract An MSW forward volume wave delay line technique for evaluating the properties of as-grown YIG films is described. Presently a qualitative measurement of the effective demagnetizing field including anisotropy contributions is obtained together with a more qualitative estimate of propagation loss. Amplitude ripple or attenuation notches due to MSW to exchange resonance coupling is easily observed. Improvements are suggested which will enable all YIG film parameters relevant to MSW device performance to be obtained.
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    Circuits, systems and signal processing 4 (1985), S. 137-156 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A major impediment to the realization of practical magnetostatic wave (MSW) devices is the inherent non-linear delay versus frequency characteristics of MSW delay lines. Most device applications require either nondispersive (delay vs. frequency slope=0) or linearly dispersive (delay vs. frequency slope = constant) characteristics. There are four basic approaches to the elimination and/or linearization of MSW dispersion: (1) modification of the magnetic film properties as a function of film thickness, (2) modification of the ground plane geometry, (3) modification of the bias field uniformity, and (4) perturbation of the propagation path surface with metal electrode reflective arrays. In principle all four approaches can yield either linearly dispersive or nondispersive characteristics with a suitable choice of bias field orientation and critical design parameters. These dispersion control techniques are reviewed, and data from recent experiments demonstrating the strengths and weaknesses of the various approaches are discussed. To date the most extensive experimental work has been done with the multiple layer (magnetic properties varied as a function of film thickness) and ground-plane spacing techniques. At present the ground-plane spacing technique produces results acceptable for some systems applications, while the multiple-layer approach is still under development.
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    Circuits, systems and signal processing 4 (1985), S. 211-219 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A recently reported experimental study of microwave tunable oscillators employing narrowband magnetostatic-wave (MSW) delay lines is reviewed. The narrowbanding was achieved by usinglifted transducers with magnetostatic surface waves (MSSWs) which yielded a bandwidth of 10 MHz with an insertion loss of less than 20dB. This approach at delay-line narrowbanding does not work as well with the other MSW wave-types because of increased insertion loss. The mode-hopping problem which beset earlier studies of MSW delay-line oscillators was overcome in the present work but now a different problem arose, viz., frequency jumping, which occurred every time the electrical length of the circuit external to the delay line changed by 360 degrees. A maximum tuning range of about 600 MHz was obtained, with this range limited primarily by the Avantek GaAs FET amplifier that was used whose electrical length was equivalent to about 45 cm of air transmission line. It was concluded that, if the electrical length of the external circuit is sufficiently reduced (ideally made zero), singlemode operation over an octave bandwidth or more is possible.
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    Circuits, systems and signal processing 4 (1985), S. 265-284 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Magneto-optical devices based on Bragg diffraction of light by magnetostatic waves (MSWs) offer the potential of large time-bandwidth optical signal processing at microwave frequencies of 1 to 20 GHz and higher. A thin-film integrated-optical configuration, with the interacting MSW and guided-optical wave both propagating in a common ferrite layer, is necessary to avoid shape-factor demagnetization effects. The underlying theory of the MSW-optical interaction is outlined, including the development of expressions for optical diffraction efficiency as a function of MSW power and frequency, device geometry, materials properties, and other relevant parameters. Recent experimental observations of anisotropic Bragg diffraction and collinear TE↔TM mode conversion induced by MSWs in yttrium iron garnet (YIG) thin films suggest that high-performance MSW integrated-optical devices are feasible. Diffraction levels as large as 4% (7-mm interaction length) and a modulation dynamic range of ∼30 db have been demonstrated. Potential signal processing applications are mentioned, including: spectrum analyzers, convolvers/correlators, deflectors, non-reciprocal optical isolators, and tunable narrowband optical filters. Advantages of these MSW-based devices over the analogous acousto-optical devices include: much greater operating frequencies, tuning through the MSW dispersion relation by varying either the rf frequency or the applied bias magnetic field, simple MSW transducer structures (e.g., a single stripline), and the potential for very high diffraction efficiencies.
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    Circuits, systems and signal processing 4 (1985), S. 317-334 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A need for microwave signal processing components ranging from simple delay lines to broadband, complex analog non-recursive transversal filters has led to the exploration of several solid-state technologies. Bulk acoustic delay lines lack spatial signal tapping and have high insertion loss. Electromagnetic delay lines have high insertion loss, limited signal processing capabilities, and are bulky. Surface acoustic wave (SAW) devices offer excellent signal processing capabilities at VHF/UHF but suffer from excessive loss at microwave frequencies and the requirement for transducers of sub-micron linewidths. However, a signal processing technology based on magnetostatic waves (MSW) propagating on epitaxial yttrium iron garnet (YIG) is emerging to fill microwave signal processing requirements. This paper summarizes the characteristics and status of magnetostatic waves and devices based on MSW, and initial experimental studies of the application of MSW devices to systems, and presents a survey of other potential areas of MSW device applications.
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    Circuits, systems and signal processing 4 (1985), S. 351-363 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Current magnetostatic wave technology applicable to EW systems is assessed. Some of the developments currently underway with dispersive and non-dispersive delay lines, tunable oscillators and bandpass filters are examined and projected performance three years from now is given. Various EW applications are then described based on these projections. This includes compressive receivers, “fast call” receivers, phased arrays, scanning receivers, and channelizers. In many instances MSW technology can replace SAW provided further improvements materialize.
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    Circuits, systems and signal processing 4 (1985), S. 503-511 
    ISSN: 1531-5878
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The Finite Time Laplace Transform unifies the basis of periodically reverse switched capacitors and periodically switched capacitors. Several examples utilizing both of these switched capacitors are given. Both capacitors have additive semi-null functions which are removed by either a staircase input signal or a post-sampler. The impedance concept is retained and the simplified analysis is more readily accessible than the ubiquitous charge analysis in the literature. There is questionable substance to allegations of a time-variant nature to any switched capacitor.
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    Circuits, systems and signal processing 4 (1985), S. 9-39 
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The present paper reviews the propagation characteristics of the three magnetostatic wave-types that can exist in a ferrimagnetic film such as the commonly used epitaxial yttrium-iron-garnet (YIG) film, viz., magnetostatic surface waves (MSSWs), magnetostatic forward volume waves (MSFVWs) and magnetostatic backward volume waves (MSBVWs). The pronounced inherent dispersiveness of these waves and methods of controlling or tailoring dispersion are discussed. Other propagation characteristics such as diffraction and propagation loss and the envelope distortion of acw pulse in propagating through such a dispersive medium are briefly described.
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    European journal of wildlife research 31 (1985), S. 3-14 
    ISSN: 1439-0574
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The stomach and colon contents of 185 common seals (Phoca vitulina L.) from the coastal shallows of Schleswig-Holstein were examined. The analysis of the food fishes is based on the investigation of otoliths. Main food species are: Gobies, flounder, plaice, smelt, dab, cod and shrimps. The composition of food changes with the age of the seals: the young ones feed mainly on shrimps, gobies and small flatfish, the older ones feed more on bigger flatfish and on a wider spectrum of species. Seasonal changes of the food composition occur. The common seal is not a specialist feeder but takes those species which are very common and/or easy to hunt.
    Abstract: Résumé Les contenus stomacaux et intestinaux de 185 phoques veaux-marins (Phoca vitulina L.) provenant du Wattenmeer (Schleswig-Holstein) ont été analysés quant à leur composition alimentaire. La détermination des différentes espèces de poissons fut réalisée par l'examen des otolithes. Les espèces les plus fréquentes sont le Goujon, le Flet, la Plie, l'Eperlan, le Cabillaud, la Limande et la Crevette. Le régime alimentaire se modifie avec l'âge du Phoque: le jeune Phoque se nourrit essentiellement de crevettes, de goujons et de plies de petite dimension, tandis que le Phoque plus âgé préfère des plies de grande dimension et recherche un éventail beaucoup plus large d'espèces. Des variations saisonnières du régime alimentaire se manifestent selon l'abondance du poisson dans le Wattenmeer. Le Phoque n'est pas une espèce à régime alimentaire spécialisé mais se nourrit d'espèces qui sont abondantes et/ou qui sont facilement accessibles.
    Notes: Zusammenfassung Magen- und Darminhalte von 185 Seehunden(Phoca vitulina L.) aus dem schleswig-holsteinischen Wattenmeer wurden auf die Zusammensetzung der Nahrung hin untersucht. Die Analyse der Fischarten erfolgte mit Hilfe der Otolithen-Bestimmung. Die häufigsten Nahrungs-Arten sind: Grundeln, Flunder, Scholle, Stint, Dorsch (Kabeljau), Kliesche und Garnelen. Die Nahrungszusammensetzung ändert sich mit dem Alter der Seehunde: Junge Tiere fressen hauptsächlich Garnelen, Grundeln und kleine Plattfische, während ältere größere Plattfische bevorzugen und ein breiteres Spektrum von Arten erjagen. Jahreszeitliche Schwankungen in der Nahrungszusammensetzung treten auf in Abhängigkeit vom Vorkommen der Fische im Wattenmeer. Der Seehund ist kein Nahrungsspezialist, sondern frißt Arten, die häufig vorkommen und/oder leicht zu erreichen sind.
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    European journal of wildlife research 31 (1985), S. 22-33 
    ISSN: 1439-0574
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary Contaminant emissions affect inanimate objects, plants, animals and humans. Such emissions can be quantified with specialised measuring equipment — without any particular technical expenditure but, rather, exact both as regards time and area. Plants as biomonitors can integrate the quantity and effect of emissions at the defined site over broader periods of time. Thanks to their mobility animals provide additional possibilities of integration throughout different areas. For the wider utilisation of the advantages of biomonitors, the important thing is to recognise the regressions and correlations between emission rates for particular substances measured from the chemical/physical/technical standpoint in specific areas and periods of time and the concentrations of these substances in defined biological samples for the same areas and periods. On this basis there arise economical possibilities for extensive and revealing collection and review of area pattern and temporal trend of contaminant pollution, for interpolation between measuring stations or extrapolation beyond measuring networks, for early recognition of unknown terrain and, in addition, early warning in relation to humans and/or the used or protected components of ecosystems. Ecologists are required to interpret analyses and interrelations. Biomonitoring and specimen banking seem to be sensible concepts. Comparatively small research expenditure on the biological/ecological side could improve and deepen the existing state of things considerably. Bioindication and biomonitoring cannot, however, dispense with calibration through physical/chemical measurements.
    Abstract: Résumé L'émission de matières toxiques agissent sur les matériaux inanimés, les plantes, les animaux, les hommes. De telles émissions se prêtent à des mesures quantitatives au moyen d' appareils adéquats — sans poser de problèmes techniques majeurs mais avec une portée ponctuelle dans l' espace et dans le temps. Des plantes indicatrices peuvent intégrer des émissions ainsi que leurs effets à un endroit déterminé sur des périodes très longues. Les animaux, en raison de leur mobilité, procurent des possibilités d' intégration complémentaires sur des fractions de l' espace. Pour une utilisation plus large des avantages des bio-indicateurs, il convient de déceler les régressions et corrélations entre les mesures des taux d' émission techno-physico-chimiques, pour des matières déterminées au sein d' échantillons biologiques définis au cours des mêmes périodes et fractions de l'espace. Cette donnée de base fournit des possibilités appréciables en vue d'un contrôle extensif et cependant révélateur de points dispersés dans l'espace ainsi que de l'évolution au cours du temps de la charge que constituent les matières toxiques, en vue d'une interpolation entre les stations de mesure ou de l'extrapolation au-delà du réseau de contrôle, ceci de manière à disposer d'une information prémonitoire pour des zones non connues et, partant, d'une indication précoce intéressant la population ou/et les composants exploités ou protégés des écosystèmes. L'interprétation des résultats d'analyse et de leurs interrelations nécessitent des écologues. Le 〉biomonitoring〈 et le 〉specimen banking〈 apparaissent comme de judicieux concepts. Un investissement scientifique relativement modeste sur le plan éco-biologique pourrait améliorer et approfondir considérablement certaines évaluations. La bio-indication et le biomonitoring ne peuvent cependant pas renoncer à l'étalonnage sur base de mesures physico-chimiques
    Notes: Zusammenfassung Schadstoffimmissionen wirken auf unbelebte Stoffe, auf Pflanzen, Tiere und Menschen. Solche Immissionen lassen sich mit geeigneten Meßgeräten quantifizieren — ohne besonderen technischen Aufwand jedoch nur punktuell, in zeitlicher und räumlicher Hinsicht. Pflanzen als Biomonitoren können Immissionsmenge und -wirkung am definierten Ort über größere Zeitspannen integrieren. Tiere bieten durch ihre Beweglichkeit zusätzliche Integrationsmöglichkeiten über Raumausschnitte. Für die breitere Nutzung der Vorteile von Biomonitoren kommt es darauf an, die Regressionen und Korrelationen zwischen chemisch-physikalisch-technisch gemessenen Immissionsraten für bestimmte Stoffe in Zeit- und Raumausschnitten mit den Konzentrationen dieser Stoffe in definierten biologischen Proben für dieselben Zeit- und Raumausschnitte zu erkennen. Auf dieser Grundlage ergeben sich preiswerte Möglichkeiten zur extensiven und doch aussagekräftigen Erfassung und Überwachung von räumlichem Muster und zeitlichem Trend von Schadstoffbelastungen, zur Interpolation zwischen Meßstationen bzw. Extrapolation über Meßnetze hinaus, für erstes Erkunden von unbekanntem Terrain und darüber hinaus zur Frühwarnung in bezug auf den Menschen und/oder auf die genuzten oder geschützten Komponenten von Ökosystemen. Zur Interpretation von Analysen und Zusammenhängen sind Ökologen nötig. „Biomonitoring“ und „Specimen Banking“ erscheinen als vernünftige Konzepte. Vergleichsweise geringer Forschungsaufwand auf biologisch-ökologischer Seite könnte bestehende Ansätze wesentlich verbessern und vertiefen. Auf die Eichung durch physikalisch-chemische Messungen können jedoch Bioindikation und Biomonitoring nicht verzichten.
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    European journal of wildlife research 31 (1985), S. 42-46 
    ISSN: 1439-0574
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The literature on the subject generally gives the following tooth-formula for the badger (Meles meles L.): 3141/3142. In several badger skulls collected in the Rückholz/Allgäu area in the years 1980 to 1983, however, the tooth pattern was different: either on the one or on both sides the first premolar was missing on the upper and lower jaw. This discovery gave rise to the examination of a larger badger-skull collection for the absence of the 1st premolar. Included in this study were the 21 badger skulls in the collection belonging to the Zoological Research Institute and Museum Alexander Koenig in Bonn, as well as the 7 badger skulls belonging to the Forschungsstelle für Jagdkunde und Wildschadenverhütung des Landes Nordrhein-Westfalen. It was found that only around 30% of the badger skulls examined had all four premolars on each jaw side. In around 22%, the 1st premolar was missing on one side of the jaw, in around 40% on two jaw sides and in around 8% even on three sides of the jaw. On this basis of the study it is suggested that the reduction of the 1st premolar be expressed in the tooth formula for the badger similar to that for the hyaena by giving the number of the premolars as 3 to 4. The tooth formula for the badger would then read correctly: 314–31/314–32.
    Abstract: Résumé Pour le Blaireau (Meles meles L.), la littérature fournit généralement la formule dentaire suivante 3141/3142. Chez la plupart des crânes de Blaireau rassemblés au cours de années 1980 à 1983 dans la région Rückholz/Allgäu apparut cependant une autre dentition: il manquait unilatéralement ou des deux côtés la première prémolaire de la mâchoire supérieure ou inférieure. Cette découverte fut le point de départ d'une recherche portant sur l'absence de la première prémolaire sur une collection de crânes de blaireaux plus importante. Cette collection fut en outre enrichie de 21 crânes de blaireaux provenant de la collection de l'Institut de Recherches zoologiques et du Musée Alexander König à Bonn de même que de 7 crânes de la «Station de Recherches de Cynégétique et de Prévention des Dégâts de Gibier du Land de Rhénanie-Westphalie». Il s'avéra que seulement 30% environ des crânes des blaireaux analysés présentaient les 4 prémolaires à chacun des maxillaires gauche et droit. Chez quelque 22% des crânes, une prémolaire faisait défaut sur une des branches des maxillaires, chez quelque 40% sur deux branches des maxillaires, chez quelque 8% sur trois des quatre branches des maxillaires. A la lumière de cette recherche, il est proposé de traduire cette réduction constatée de la première molaire chez le Blaireau de façon analogue à ce qui se fait pour la formule dentaire de l'Hygène, pour laquelle le nombre de prémolaires est indiqué par 3 à 4. La formule dentaire du Blaireau doit dès lors s'énoncer plus correctement de la façon suivante: 314–31/314–32.
    Notes: Zusammenfassung Für den Dachs (Meles meles L.) wird in der Literatur allgemein folgende Zahnformel angegeben: 3141/3142. Bei mehreren im Raum Rückholz/Allgäu in den Jahren von 1980 bis 1983 gesammelten Dachsschädeln fand sich jedoch eine andere Bezahnung; es fehlte ein- oder beidseitig im Ober- bzw. Unterkiefer der 1. Praemolar. Dieser Befund war Veranlassung, eine größere Dachsschädel-Kollektion auf das Fehlen des 1. Praemolaren zu untersuchen. Einbezogen wurden in diese Untersuchung die 21 Dachsschädel der Sammlung des Zoologischen Forschungsinstituts und Museums Alexander Koenig, Bonn, sowie die 7 Dachsschädel der Forschungsstelle für Jagdkunde und Wildschadenverhütung des Landes Nordrhein-Westfalen. Gefunden wurde, daß nur noch ca. 30% der untersuchten Dachsschädel in jedem Kieferast alle vier Praemolaren aufwiesen. Bei ca. 22% fehlte der 1. Praemolar in einem Kieferast, bei ca. 40% in zwei Kieferästen und bei ca. 8% sogar bereits in drei Kieferästen. Aufgrund der Untersuchung wird vorgeschlagen, die vorgefundene Reduktion des 1. Praemolaren in der Zahnformel für den Dachs analog der Zahnformel bei der Hyäne zum Ausdruck zu bringen, indem die Anzahl der Praemolaren mit 3 bis 4 angegeben wird. Die Zahnformel für den Dachs müßte mithin richtigerweise wie folgt lauten: 314–31/314–32
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    European journal of wildlife research 31 (1985), S. 60-62 
    ISSN: 1439-0574
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Mathematical programming 32 (1985), S. 249-277 
    ISSN: 1436-4646
    Keywords: Minisum Locations ; Location-Allocation ; Network Location ; Dynamic Location
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper, we consider multiperiod minisum location problems on networks in which demands can occur continuously on links according to a uniform probability density function. In addition, demands may change dynamically over time periods and at most one facility can be located per time period. Two types of networks are considered in conjunction with three behavioral strategies. The first type of network discussed is a chain graph. A myopic strategy and long-range strategy for locatingp-facilities are considered, as is a discounted present worth strategy for locating two facilities. Although these problems are generally nonconvex, effective methods are developed to readily identify all local and global minima. This analysis forms the basis for similar problems on tree graphs. In particular, we construct algorithms for the 3-facility myopic problem and the 2-facility long-range and discounted cost problems on a tree graph. Extensions and suggestions for further research on problems involving more general networks are provided.
    Type of Medium: Electronic Resource
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  • 98
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    Electronic Resource
    Springer
    Mathematical programming 32 (1985), S. 366-370 
    ISSN: 1436-4646
    Keywords: Cores ; Dual Prices ; Linear Production Games
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Consider a game in which resources may be combined to produce products of known values. For linear production processes, the game may be characterized by a family of linear programs. It is shown that appropriately defined market prices for the resources coincide with the set of optimal dual solutions to one of these linear programs. This result generalizes and unifies the known cases in game theory, in which the core of a game coincides with the set of dual optimal solutions to a corresponding master linear programming problem.
    Type of Medium: Electronic Resource
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  • 99
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    Mathematical programming 33 (1985), S. 61-67 
    ISSN: 1436-4646
    Keywords: Conjugate Gradient Methods ; Global Convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The paper examines a method of implementing an angle test for determining when to restart conjugate gradient methods in a steepest descent direction. The test is based on guaranteeing that the cosine of the angle between the search direction and the negative gradient is within a constant multiple of the cosine of the angle between the Fletcher-Reeves search direction and the negative gradient. This guarantees convergence, for the Fletcher-Reeves method is known to converge. Numerical results indicate little, if anything, is lost in efficiency, and indicate gains may well be possible for large problems.
    Type of Medium: Electronic Resource
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  • 100
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    Mathematical programming 33 (1985), S. 120-121 
    ISSN: 1436-4646
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Type of Medium: Electronic Resource
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