Mesoscopic organization reveals the constraints governing C. elegans nervous system

One of the biggest challenges in biology is to understand how activity at the cellular level of neurons, as a result of their mutual interactions, leads to the observed behavior of an organism responding to a variety of environmental stimuli. Investigating the intermediate or mesoscopic level of organization in the nervous system is a vital step towards understanding how the integration of micro-level dynamics results in macro-level functioning. In this paper, we have considered the somatic nervous system of the nematode Caenorhabditis elegans, for which the entire neuronal connectivity diagram is known. We focus on the organization of the system into modules, i.e., neuronal groups having relatively higher connection density compared to that of the overall network. We show that this mesoscopic feature cannot be explained exclusively in terms of considerations, such as optimizing for resource constraints (viz., total wiring cost) and communication efficiency (i.e., network path length). Comparison with other complex networks designed for efficient transport (of signals or resources) implies that neuronal networks form a distinct class. This suggests that the principal function of the network, viz., processing of sensory information resulting in appropriate motor response, may be playing a vital role in determining the connection topology. Using modular spectral analysis, we make explicit the intimate relation between function and structure in the nervous system. This is further brought out by identifying functionally critical neurons purely on the basis of patterns of intra- and inter-modular connections. Our study reveals how the design of the nervous system reflects several constraints, including its key functional role as a processor of information.Comment: Published version, Minor modifications, 16 pages, 9 figure

Adjusting process count on demand for petascale global optimization⋆

There are many challenges that need to be met before efficient and reliable computation at the petascale is possible. Many scientific and engineering codes running at the petascale are likely to be memory intensive, which makes thrashing a serious problem for many petascale applications. One way to overcome this challenge is to use a dynamic number of processes, so that the total amount of memory available for the computation can be increased on demand. This paper describes modifications made to the massively parallel global optimization code pVTdirect in order to allow for a dynamic number of processes. In particular, the modified version of the code monitors memory use and spawns new processes if the amount of available memory is determined to be insufficient. The primary design challenges are discussed, and performance results are presented and analyzed

Networked Computing in Wireless Sensor Networks for Structural Health Monitoring

This paper studies the problem of distributed computation over a network of wireless sensors. While this problem applies to many emerging applications, to keep our discussion concrete we will focus on sensor networks used for structural health monitoring. Within this context, the heaviest computation is to determine the singular value decomposition (SVD) to extract mode shapes (eigenvectors) of a structure. Compared to collecting raw vibration data and performing SVD at a central location, computing SVD within the network can result in significantly lower energy consumption and delay. Using recent results on decomposing SVD, a well-known centralized operation, into components, we seek to determine a near-optimal communication structure that enables the distribution of this computation and the reassembly of the final results, with the objective of minimizing energy consumption subject to a computational delay constraint. We show that this reduces to a generalized clustering problem; a cluster forms a unit on which a component of the overall computation is performed. We establish that this problem is NP-hard. By relaxing the delay constraint, we derive a lower bound to this problem. We then propose an integer linear program (ILP) to solve the constrained problem exactly as well as an approximate algorithm with a proven approximation ratio. We further present a distributed version of the approximate algorithm. We present both simulation and experimentation results to demonstrate the effectiveness of these algorithms

Development of the City Public Service Model on the Basis of Integrated Transport Flow Indicators

The problem of modeling public services based on architectural and planning decisions is considered, the role of traffic in the formation of a model of city services is analyzed. An integrated criterion for the quality of public services is proposed. A method has been developed for determining segmented public services taking into account the transport areas of the city, which will make it possible to evenly disperse public service centers. The basis is a socio-planning organization, as a material-spatial system containing anthropogenic and natural components – the territory and institutions where the functional processes that take place in the urban planning environment take place. The described model has certain versatility, and is simultaneously suitable for characterizing various categories of service institutions. Thus, the task of optimizing the quality of public services in the city is reduced to a mathematical model for which, by setting the basic design criteria, the optimal result can be obtained.On the basis of a questionnaire survey and analysis of statistical data, calculation of traffic intensity, the demand and supply of the level of public services фre studied. The structural elements of this model: population, territory, transport and service institutions, are in dialectical interaction, which is described by the mathematical model in this study. The model is based on the calculation of the minimum population in the service area, which allows to have i-th type establishments using the social potential method, as well as a graph-analytical method in determining the optimal location of service institutions in the city.As a result of the research, a conceptual model of public services for cities is built, a layout of supermarkets in the territory of Uzhhorod and distribution of service areas of these institutions is proposed. This optimization will ensure uniform domestic servicing of the territory, optimal performance indicators of service establishments and minimum average service radii of points