Measuring a mitotic oscillator: The ARC discontinuity

Mitosis occurs synchronously in up to 10⁸ nuclei in the syncytial plasmodium ofPhysarum polycephalum. Any two phases of the mitotic cycle may be mixed by fusing plasmodial pairs. A topological property of the synchronized phase of the fused pair as a function of parental phases, the arc discontinuity, characterizes the underlying oscillator, and indicates mitosis is controlled by a moderate relaxation oscillator which rotates more rapidly near its singularity than its limit cycle. A model oscillator is briefly described. Proceedings article from the Dissipative Structures Section of the Tenth Symposium on Biomathematics and Computer Science in the Life Sciences, University of Texas, Houston. March 29–31, 1973. Symposium Chairman: Stuart O. Zimmerman. Session Chairman and Proceedings Editors: Charles Walter and Hugo M. Martinez.     

The global asymptotic stability of prey-predator systems with second-order dissipation

Models of biological development, evolution and control should take into account that very small numbers of cells or chemicals or individuals eventually grow into stable, large populations. The simplified two-component model used in these studies includes the following: (1) first-order decay; (2) first-order autocatalysis; (3) negative feedback; (4) positive feedback; (5) second-order decay; (6) second-order autocatalysis. A positive definite Lyapunov function is constructed and shown to have a negative definite total derivative. The stationary statex>0,y>0, therefore possesses global asymptotic stability. This means that sustained oscillations cannot occur. Another stationary state,x=y=0, is shown to be unstable. This means that infinitesimally small perturbations ofx=y=0 will result in evolution of the variables to the stable stationary state. This result contrasts with that obtained with the Lotka-Volterra model in that small perturbations ofx=y=0 for that model result in sustained, oscillating excursions; the smaller the initial perturbations, the larger these excursions will be. A simulation illustrates that stable populations of 10²⁰ x's andy's can arise from a singlex andy.x grows more or less continuously, buty remains extremely small for 80 per cent of the time interval required for the variables to approach their stable populations. Proceedings article from the Dissipative Structures section of the Tenth Symposium on Biomathematics and Computer Science in the Life Sciences, University of Texas, Houston. March 29–31, 1973. Symposium Chairman: Stuart O. Zimmerman. Session Chairman and Proceedings Editors: Charles Walter and Hugo M. Martinez.     

Algebraic properties of automata associated to Petri nets and applications to computation in biological systems

Biochemical and genetic regulatory networks are often modeled by Petri nets. We study the algebraic structure of the computations carried out by Petri nets from the viewpoint of algebraic automata theory. Petri nets comprise a formalized graphical modeling language, often used to describe computation occurring within biochemical and genetic regulatory networks, but the semantics may be interpreted in different ways in the realm of automata. Therefore, there are several different ways to turn a Petri net into a state-transition automaton. Here, we systematically investigate different conversion methods and describe cases where they may yield radically different algebraic structures. We focus on the existence of group components of the corresponding transformation semigroups, as these reflect symmetries of the computation occurring within the biological system under study. Results are illustrated by applications to the Petri net modelling of intermediary metabolism. Petri nets with inhibition are shown to be computationally rich, regardless of the particular interpretation method. Along these lines we provide a mathematical argument suggesting a reason for the apparent all-pervasiveness of inhibitory connections in living systems.     

Buchbesprechungen/Book Reviews

Book reviewed in this article:
Grossbard, E. , Hatfield Polytechnic, UK., Straw Decay and Its Effect on Disposal and Utilization. Proceedings of a Symposium on Straw Decay and Workshop on Assessment Techniques, held at Hatfield Polytedhnic, April 10–11th 1979.     

Book Reviews

Book Review in This Article:
É cologie M icrobienne du S ol . Y. Dommergues and F. Mangenot
I nfections and I mmunosuppression in S ubhuman P rimates —The Proceedings of the International Symposium on Infections and Immunosuppression in Subhuman Primates, Rijswijk, December 1969, organized jointly by the World Health Organization and the Radiobiological Institute, TNO, Holland. Edited by H. Balner and W. I. B. Beveridge.     

Reviews of publications

Insects-Plants. Proceedings of the 6th International Symposium on Insect—Plant Relationships, Pau, France, 1986, edited by V. Labeyrie, G. Fabres & D. Lachaise. Dordrecht: W. Junk, 1987
In vitro Culture of Higher Plants , by R. L. M. Pierik     

Book reviews

Book reviewed in this article: Fruit Flies of Economic Significance: Their Identification and Bionomics. By Ian M. White and Marlene M. Elson-Harris. Arthropods of Medical and Veterinary Importance . A checklist of preferred names and allied terms. Compiled by A.R. Pittaway. Behaviour and Impact of Aphidophaga [Proceedings of the 4th meeting of the IOBC working group ‘Ecology of Aphidophaga’], Edited by Polgar, L., R. J. Chambers, A. F. G. Dixon and I. Hodek. Proceedings of the 7^th International Symposium on Insect-Plant Relationships     

Book Review

Book review in this article:
Sly, P.G . (Ed.) (1982) Sediment/Freshwater Interaction: Proceedings of the Second International Symposium .     

Book reviews

Book reviewed in this article: Marjory A. Hoy (Ed.): Recent Advances in Knowledge of the Phytoseiidae J. H. Visser and A. K. Minks (Eds.). Proceedings of the 5th International Symposium on Insect-Plant Relationships R. C. Rainey (Ed.): Biona Reports 1 & 2: Insect Flight.     

Bird origins and evolution: data accumulates, scientists integrate, and yet the "debate" still rages

book reviewed in this article
New Perspectives on the Origin and Early Evolution of Birds:Proceedings of the International Symposium in Honor of John H.Ostrom.Edited by Jacques Gauthier and Lawrence F.Gall.     

Fundamentals of estimating the net benefits of ecosystem preservation: the case of the Salton Sea

This article, both theoretical and methodological in nature, argues the potential merits of using a net benefits’ framework as a tool to aid policy makers in their efforts to compare Salton Sea restoration alternatives and inform the public as to the potential magnitude and distribution of trade-offs associated with each alternative. A net benefits’ approach can provide a more accurate comparison and evaluation of the potential net returns from public spending on Salton Sea restoration than what would be provided under the suggested criteria of current legislative mandates. Furthermore, a net benefits’ framework provides a more lucid and systematic accounting framework by which to enumerate the full array of benefits and costs of each alternative for policy analysis. Finally, net benefits’ analysis serves to add transparency to the decision-making process so that the public gains an understanding of how its scarce resources, including both financial and natural capital, are being appropriated. Additionally, we illustrate and emphasize the importance of estimating the non-market values associated with many of the ecosystem services provided by the Salton Sea and describe the major techniques that do so. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005     

Stereometry in very close-range stereophotogrammetry with non-metric cameras for human movement analysis

In this paper a stereophotogrammetric algorithm based on a black-box approach to the modelling of object to image spaces relationship is proposed. The algorithm is well suited for 'very close-range photogrammetry', with respect to experiments in which the measurement field is 0.5 X 0.5 X 0.5 m or smaller, as in the analysis of a few or small body segments movements. The attainable accuracy is high, better than 0.1% of the observation distance. Non-professional and even different cameras can be used. Consequently an inexpensive experimental set-up can be realized. A very simple, cheap and easily usable calibration object is needed. Computation time for the reconstruction of object-space co-ordinates of point body landmarks is one order of magnitude lower than in the case of the Direct Linear Transformation (DLT) (Abdel Aziz and Karara, Proceedings of the ASP/U1 Symposium on Close-Range Photogrammetry, pp. 1-18. American Society of Photogrammetry, 1971; Marzan and Karara, Proceedings of the Symposium on close-range Photogrammetric Systems, pp. 420-467. American Society of Photogrammetry, 1975). Computation time for calibration is two-fold in respect of the DLT. An example of application to the recording of the movements of the index finger with respect to the metacarpophalangeal joint is given.     

Book notices

INSECT HORMONES. By V. J. A. Novak
PHASE AND CASTE DETERMINATION IN INSECTS. ENDOCRINE ASPECTS. Papers presented at a Symposium of the Section Physiology and Biochemistry of the XV International Congress of Entomology, Washington, D.C., 1976 (Chairman: Dorothy Feir). Edited by Martin Lüscher
A BIOLOGY OF LOCUSTS. By R. F. Chapman     

21st century zoo design

A review of Conservation Centres for the New Millennium. Proceedings of the 5^th International Symposium on Zoo Design, edited by Amy B. Plowman and Peter M.C. Stevens. Paignton, Devon, U.K.: Whitely Wildlife Conservation Trust, 1999, 181 pp., paperback.     

Sachregister

Book reviews in this article: Szegi, J. , ed., Proceedings of the Symposium on Soil Microbiology (Symposia Biologica Hungarica, Vol. 11). Metzner, H. , Biochemie der Pflanzen. Microautoradiography and Electron Probe Analysis . Their Application to Plant Physiology.     

Biological monitoring of fish and crustaceans in the Wadden Sea — potential and problems

Monitoring of fish and crustaceans in the Wadden Sea (WS) must cope with rapid changes in distribution patterns, access to certain areas and gear efficiency. Application and limitations of a variety of fishing devices (fyke nets, gill nets, enclosures, stow nets, purse seines, beam trawls, push nets, beach seines, bottom trawls, pelagic trawls) are discussed with regard to different objectives of monitoring. Furthermore, the validity of data from three current monitoring programmes is also discussed. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

International Symposium on the Evaluation of Butadiene and Chloroprene Health Risks

These proceedings represent nearly all the platform and poster presentations given during the International Symposium on Evaluation of Butadiene and Chloroprene Health Risks, held in Charleston, South Carolina, USA, on September 20-22, 2005. The Symposium was attended by 78 participants representing private industry (37), academia (21), government (11), not-for-profit organizations (5), and consulting (4). The program followed the format of previous symposia on butadiene, chloroprene, and isoprene in London UK (2000) and butadiene and isoprene in Blaine, Washington USA (1995). This format enabled the exchange of significant new scientific results and discussion of future research needs. Isoprene was not evaluated during the 2005 Symposium because of lack of new data. For background information, the reader is referred to the proceedings of the London 2000 meeting for a thorough historical perspective and overview of scientific and regulatory issues concerning butadiene, chloroprene, and isoprene [Chem.-Biol. Interact. (2001) 135-136:1-7]. The Symposium consisted of seven sessions: (1) Introduction and Opening Remarks, (2) Butadiene/styrene-butadiene rubber (SBR)--Process Overview, Exposure and Health Effects/Human Studies; (3) Chloroprene--Process Overview, Exposure and Health Effects/Human Studies; (4) Mode of Action/Key Events; (5) Risk Assessment; (6) Poster Presentations; and (7) Panel Discussion and Future Directions. The Symposium concluded with a discussion by all participants of issues that arose throughout the course of the Symposium. The Proceedings of the Symposium published in this Special Issue are organized according to the Sessions outlined above. The purpose of this foreword is to summarize the presentations and their key findings and recommend future research directions for each chemical.     

Determining the roles of different chain fragments in recognition of immunoglobulin fold

We examine sequence-to-structure specificity of beta-structural fragments of immunoglobulin domains. The structure specificity of separate chain fragments is estimated by computing the Z-score values in recognition of the native structure in gapless threading tests. To improve the accuracy of our calculations we use energy averaging over diverse homologs of immunoglobulin domains. We show that the interactions between residues of beta-structure are more determinant in recognition of the native structure than the interactions within the whole chain molecule. This result distinguishes immunoglobulins from more typical proteins where the interactions between residues of the whole chain normally recognize the native fold more accurately than interactions between the residues of the secondary structure residues alone [Reva,B. and Topiol,S. (2000) BIOCOMPUTING: Proceedings of the Pacific Symposium. World Scientific Publishing Co., pp. 168-178]. We also find that the predominant contributions of the secondary structure are produced by the four central beta-strands that form the core of the molecule. The results of this study allow us through quantitative means to understand the architecture of immunoglobulin molecules. Comparing the fold recognition data for different chain fragments one can say that beta-strands form a rigid frame for immunoglobulin molecules, whereas loops, with no structural role, can develop a broad variety of binding specificities. It is well known that protein function is determined by specific portions of a protein chain. This study suggests that the whole protein structure can be predominantly determined by a few fragments of chain which form the structural framework of the molecule. This idea may help in better understanding the mechanisms of protein evolution: strengthening a protein structure in the key framework-forming regions allows mutations and flexibility in other chain regions.     

Homogeneous nets of neuron-like elements

Propagation and reverberation of excitation patterns are investigated for 1-dimensional and 2-dimensional homogeneous nets of neuron-like elements. A 1-dimensional net has a proper set of excitation patterns which only can be conducted in the net. Such a net has an ability of discriminating and shaping stimulus signals. Two types of self-reproducing reverberatory excitation patterns are shown for 2-dimensional homogeneous nets. An algebraic theory of general homogeneous nets is also developed.