Efficient Parallel Graph Algorithms for Coarse-Grained Multicomputers and BSP

In this paper we present deterministic parallel algorithms for the coarse-grained multicomputer (CGM) and bulk synchronous parallel (BSP) models for solving the following well-known graph problems: (1) list ranking, (2) Euler tour construction in a tree, (3) computing the connected components and spanning forest, (4) lowest common ancestor preprocessing, (5) tree contraction and expression tree evaluation, (6) computing an ear decomposition or open ear decomposition, and (7) 2-edge connectivity and biconnectivity (testing and component computation). The algorithms require O(log p) communication rounds with linear sequential work per round (p = no. processors, N = total input size). Each processor creates, during the entire algorithm, messages of total size O(log (p) (N/p)) . The algorithms assume that the local memory per processor (i.e., N/p ) is larger than p ^ε , for some fixed ε > 0 . Our results imply BSP algorithms with O(log p) supersteps, O(g log (p) (N/p)) communication time, and O(log (p) (N/p)) local computation time. It is important to observe that the number of communication rounds/ supersteps obtained in this paper is independent of the problem size, and grows only logarithmically with respect to p . With growing problem size, only the sizes of the messages grow but the total number of messages remains unchanged. Due to the considerable protocol overhead associated with each message transmission, this is an important property. The result for Problem (1) is a considerable improvement over those previously reported. The algorithms for Problems (2)—(7) are the first practically relevant parallel algorithms for these standard graph problems. Received July 5, 2000; revised April 16, 2001.     

Naive statics: Current misconceptions on equilibrium.

Studied common concepts regarding the equilibrium of objects in 3 experiments, using a total of 85 17–45 yr old Ss. Groups of Ss (including some experts in statics) were asked to solve problems like finding the resting position of objects suspended either by their center of gravity or at some point more or less removed from the center of gravity. Results show that, with few exceptions, Ss confused neutral equilibrium with the stable equilibrium that is assumed when the object is symmetrical with its vertical axis. This error is explained, together with the errors found in tasks in which objects were not suspended by their center of gravity, by the hypothesis that Ss conceive equilibrium as an equaling of the potential energy of gravity. The possibility that Ss' mistakes may be due to an impression of equilibrium connected to conditions of perfect symmetry is discussed, as is the hypothesis of the coexistence of naive and objective concepts in the human system of knowledge. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation between the redox state of iron-based nanoparticles and their cytotoxicity toward Escherichia coli

Iron-based nanoparticles have been proposed for an increasing number of biomedical or environmental applications although in vitro toxicity has been observed. The aim of this study was to understand the relationship between the redox state of iron-based nanoparticles and their cytotoxicity toward a Gram-negative bacterium, Escherichia coli. While chemically stable nanoparticles (gammaFe2O3) have no apparent cytotoxicity, nanoparticles containing ferrous and, particularly, zerovalent iron are cytotoxic. The cytotoxic effects appear to be associated principally with an oxidative stress as demonstrated using a mutant strain of E. coli completely devoid of superoxide dismutase activity. This stress can result from the generation of reactive oxygen species with the interplay of oxygen with reduced iron species (Fe(II) and/or Fe(0)) or from the disturbance of the electronic and/or ionic transport chains due to the strong affinity of the nanoparticles for the cell membrane.     

New insights into the psychological dimension of wood–human interaction

The effect a wooden-built environment exerts on the physical and psychological well-being of people has mostly been investigated by evaluation, through a limited number of sensory modalities, of small size stimuli. In this research, two real-size wooden and plaster indoor settings were used to examine the influence of wood on people’s emotions and perceptions. Three questionnaires assessed participants’ multimodal sensory, affective, and cognitive responses to the settings (Semantic Differential questionnaire), their emotional state (Positive and Negative Affect Schedule), and their environmental behaviour and biophilia degree (Nature Relatedness Scale). The results revealed that wood induces more positive emotions than plaster, and that individual biophilia degree appears to influence the tactile, auditory, and olfactory evaluation of the settings. It furthermore indicates how wood used in real buildings positively influences human psychological well-being and highlights the importance of considering multiple sensory modalities when investigating wood–human interaction.     

A general framework for trajectory data warehousing and visual OLAP

In this paper we present a formal framework for modelling a trajectory data warehouse (TDW), namely a data warehouse aimed at storing aggregate information on trajectories of moving objects, which also offers visual OLAP operations for data analysis. The data warehouse model includes both temporal and spatial dimensions, and it is flexible and general enough to deal with objects that are either completely free or constrained in their movements (e.g., they move along a road network). In particular, the spatial dimension and the associated concept hierarchy reflect the structure of the environment in which the objects travel. Moreover, we cope with some issues related to the efficient computation of aggregate measures, as needed for implementing roll-up operations. The TDW and its visual interface allow one to investigate the behaviour of objects inside a given area as well as the movements of objects between areas in the same neighbourhood. A user can easily navigate the aggregate measures obtained from OLAP queries at different granularities, and get overall views in time and in space of the measures, as well as a focused view on specific measures, spatial areas, or temporal intervals. We discuss two application scenarios of our TDW, namely road traffic and vessel movement analysis, for which we built prototype systems. They mainly differ in the kind of information available for the moving objects under observation and their movement constraints.     

Thermochemical or hybrid cycles of hydrogen production—technico-economical comparison with water electrolysis

The creation, by means of a computer, of numerous thermochemical cycles allowed a general evaluation of the energy and economic outputs of this process. In the energy field, the thermochemical process is theoretically equivalent to the electrolytic line but its irreversibilities are heavier. The large amount of raw materials to be produced in each reaction of a thermochemical cycle will require too high investment costs to make this process economically competitive. Addition of electric energy in a hybrid cycle improves slightly the efficiency and decreases the amount of materials to be handled; therefore lower investment costs are needed. However, these characteristics remain insufficient to compete with direct electrolysis.Direct electrolysis of water seems to be the best way for a mass production of hydrogen by water decomposition.     

Rigid and non-rigid kinetic depth effect with rotating discrete helices

To determine any difference of TV viewing attitude between normal and hearing-loss children, 14 normal and 8 sensory impaired infants/toddlers were observed separately in a playroom with a TV set showing a 12-min videotape. All children enjoyed TV and showed clear differences in TV viewing behavior between hearing-loss and auditory normal children. At the beginning of their favorite programs or changes in programs, normal infants/toddlers were quickly aware of the TV sound and turned toward the TV set, where as hearing-loss children remained unaware. Our observation proved the intact hearing of two clients who had not responded to regular infant auditory tests. Moreover, we surveyed 65 hearing-loss children. Only 21% of them began to watch TV at 0 year of age, 50% at 1 year. They did it apparently later than normal infants who began to watch TV mostly before 1 year of age in the Japanese general population. From fitting with a hearing aid, however, most of them began to enjoy TV, watch it longer, have their favorite programs (music, songs, etc.) and turn to face the TV whenever a favorite program began. This suggests hearing acuity is important to enjoy TV. Since TV is already familiar and attractive to most any children, it is a useful and sensitive tool for early detection of hearing-loss children at 6-18 months of age.