Rotifer Population Dynamics in Two Coupled Habitats: Invasion of Chaos

We study the role of interactions between habitats in rotifer dynamics. We use a simple discrete-time model to simulate the interactions between neighboring habitats with different intrinsic dynamics. Being uncoupled, one habitat shows periodical oscillations of the rotifer biomass while the other one demonstrates chaotic oscillations. As a result of the exchange of rotifer biomass, chaos replaces regular oscillations. As a result, the rotifer dynamics becomes chaotic in both habitats. We show that the invasion of chaos is followed by the synchronization of the chaotic regimes of both habitats, and this synchronization increases as coupling between the habitats is increased. We also demonstrate that the biological invasion of the rotifer species, which show chaotic dynamics, to a neighboring habitat with intrinsically regular plankton dynamics leads to the invasion of chaos and the synchronization of chaotic oscillations of the plankton biomass in both the habitats.     

Two site-single carrier transport kinetics

Rate equations have been developed which describe the concentration dependence for ion absorption by a two site-single carrier transport system for those cases in which the ion transport can be considered to be formally equivalent with an enzymic process. Comparison of this type of transport is made with ion transport via a one site-two carrier transport system. The equations developed are also applicable to enzymic processes catalysed by an enzyme having two substrate binding sites.     

Advances in synthetic biology: on the path from prototypes to applications

Synthetic biology combines knowledge from various disciplines including molecular biology, engineering, mathematics and physics to design and build novel proteins, genetic circuits and metabolic networks. Early efforts aimed at altering the behavior of individual elements have now evolved to focus on the construction of complex networks in single-cell and multicellular systems. Recent achievements include the development of sophisticated non-native behaviors such as bi-stability, oscillations, proteins customized for biosensing, optimized drug synthesis and programmed spatial pattern formation. The de novo construction of such systems offers valuable quantitative insight into naturally occurring information processing activities. Furthermore, as the techniques for system design, synthesis and optimization mature, we will witness a rapid growth in the capabilities of synthetic systems with a wide-range of applications.     

具有共生作用两种群离散耦合Logistic模型混沌控制

针对具有共生作用的离散耦合Logistic模型,首先采用Lyapunov指数方法验证了混沌现象的存在.然后详细地分析了系统随参数变化的分岔图,发现了系统中存在更复杂的现象.最后应用混沌跟踪控制方法控制系统的混沌现象,使得种群稳定到正不动点轨道上,消除了种群中存在的混沌现象.仿真结果验证了控制方法的有效性.     

Chaos: principles and implications in biology

In this paper we review some of the basic principles of thetheory of dynamical systems. We introduce the reader to thedefinition of chaos and strange attractors and we discuss theirimplications in biology. Received on June 9, 1988; accepted on October 24, 1988     

Re-establishability in abstract biology

It is shown that any (ℳ ℛ) has some component which cannot be re-established after it has been inhibited. If there is only one such component, it must be central, that is, its inhibition stops the whole system. These results hold even when it is not assumed that ℳ is connected.     

Two semantic brain systems for rapid and slow differentiation of the abstract and concrete words

In the previous studies, semantic processing was repeatedly found to be reflected in the late (300-800 ms) components of event-related potentials (ERP). However, a human may catch the meaning of the words much earlier. In this work we investigated brain mechanisms of semantic analysis of abstract and concrete written words in four experimental conditions: (1) simple reading (a subjects had to read words to him/herself); (2) simple classification (a subjects had to classify presented words into abstract and concrete categories); (3) cued and (4) uncued selective classification conditions (a subject had to classify only the words typed in a particular color). In the simple reading condition, early (40-100 ms) differences between the ERPs to concrete and abstract words were found mostly in the right frontal areas. During simple classification, the early differences between the ERPs were observed in more dorsal areas. Differences in the late ERP components (450-700 ms) in the left frontal area were characteristic of all cases of explicitly classified words. The findings suggest the existence of two semantic systems: a rapid implicit system which involves the right frontal cortex and can be suppressed by task demands, and a slow explicit system of word classification involving, predominantly, the left frontal area.     

BioText Search Engine: beyond abstract search

The BioText Search Engine is a freely available Web-based application that provides biologists with new ways to access the scientific literature. One novel feature is the ability to search and browse article figures and their captions. A grid view juxtaposes many different figures associated with the same keywords, providing new insight into the literature. An abstract/title search and list view shows at a glance many of the figures associated with each article. The interface is carefully designed according to usability principles and techniques. The search engine is a work in progress, and more functionality will be added over time. Availability: http://biosearch.berkeley.edu.     

Two conformational states of Ras GTPase exhibit differential GTP-binding kinetics

Previous ³¹P NMR studies revealed that small GTPases H-Ras and K-Ras in complex with GTP assume two interconverting conformational states, state 1 and state 2. While state 2 corresponds to an active conformation, little is known about the function of state 1, an inactive conformation incapable of effector binding. To address the biochemical properties of state 1, we measured the ³¹P NMR spectra of five Ras family small GTPases; H-Ras, M-Ras, Rap1A, Rap2A and RalA, and find that they exhibit distinctive state 2/state 1 populations with the ratios ranging from 0.072 for M-Ras to 16 for Rap2A. Further, we show that GTPases with higher populations of state 1 exhibit higher dissociation and association rate constants for GTP. These results imply that GTP loading to the nucleotide-free small GTPases preferentially yields state 1, which is subsequently converted to state 2, rendering the GTP-bound form functional.     

Chaos in percepts?

Multistability in perceptual tasks has suggested that the mechanisms underlying our percepts might be modeled as nonlinear, deterministic systems that exhibit chaotic behavior. We present evidence supporting this view, obtaining an estimate of 3.5 for the dimensionality of such a system. A surprising result is that this estimate applies for a rather diverse range of perceptual tasks. Received: 22 April 1993/Accepted in revised form: 6 August 1993     

Navigating abstract virtual environment: an eeg study

Perceptions of different environments are different for different people. An abstract designed environment, with a degree of freedom from any visual reference in the physical world requests a completely different perception than a fully or semi-designed environment that has some correlation with the physical world. Maximal evidence on the manner in which the human brain is involved/operates in dealing with such novel perception comes from neuropsychology. Harnessing the tools and techniques involved in the domain of neuropsychology, the paper presents nee evidence on the role of pre-central gyrus in the perception of abstract spatial environments. In order to do so, the research team developed three different categories of designed environment with different characteristics: (1) Abstract environment, (2) Semi-designed environment, (3) Fully designed environment, as experimental sample environments. Perception of Fully-designed and semi-designed environments is almost the same, [maybe] since the brain can find a correlation between designed environments and already experienced physical world. In addition to this, the response to questionnaires accompanied with a list of buzzwords that have been provided after the experiments, also describe the characteristics of the chosen sample environments. Additionally, these results confirm the suitability of continuous electroencephalography (EEG) for studying Perception from the perspective of architectural environments.     

Chaos in biology.

This paper presents a brief and pedagogical account of the relevance of chaos theory in biology. A few caveats to avoid misleading interpretations are underlined, for instance the required determinism and consistency of the experimental time series. The selective advantage offered by a properly controlled chaotic dynamics is discussed on the examples of cardiac rhythm and brain dynamics.