Different Dynamics (different + dynamics)

Distribution by Scientific Domains


Selected Abstracts


Segregation of temporal and spatial distribution between kleptoparasites and parasitoids of the eusocial sweat bee, Lasioglossum malachurum (Hymenoptera: Halictidae, Mutillidae)

ENTOMOLOGICAL SCIENCE, Issue 2 2009
Carlo POLIDORI
Abstract Cuckoo bees and velvet ants use different resources of their shared host bees, the former laying eggs on the host pollen stores and the latter on immature stages. We studied the activity patterns of the cuckoo bee Sphecodes monilicornis and the velvet ant Myrmilla capitata at two nesting sites of their host, the social digger bee Lasioglossum malachurum, over a 3 year period. Due to the difference in host exploitation, we expected different temporal patterns of the two natural enemies as well as a positive spatial association with host nest density for both species. At a daily level, S. monilicornis was more abundant between 10.00 and 15.00 h, while M. capitata was most active in the early morning and late afternoon; both species activities were independent from host provisioning activity. The activity of cuckoo bees was in general positively correlated with the density of open host nests (but not with the total number of nests), while that of velvet ants was rarely correlated with this factor. Sphecodes monilicornis was seen both attacking the guard bees and directly entering into the host nests or digging close to nest entrances, while M. capitata only gained access to host nests through digging. We conclude that the temporal and spatial segregation between the two species may be, at least partially, explained both by the different resources exploited and by the different dynamics of host interactions. [source]


Dynamics of heat-induced thermal stress resistance and hsp70 expression in the springtail, Orchesella cincta

FUNCTIONAL ECOLOGY, Issue 2 2009
Simon Bahrndorff
Summary 1The relationship between thermal resistance and expression of inducible heat shock proteins, especially Hsp70, depends on the species and temperature treatments. The induction of Hsp70 has been shown to be essential for heat stress survival in a number of species, yet the maximum protein expression levels do not coincide with peak survival after heat hardening in Drosophila. 2Here we study the functional relationship between heat-induced expression of the heat shock protein Hsp70, and thermal resistance in adult Orchesella cincta by comparing thermal resistance (survival of 37·4 °C for 60 min) with Hsp70 gene and protein expression levels, all three measured at time points 2, 4, 6, 23, 27, 49 h after a heat hardening treatment (35·4 °C for 60 min). 3Thermotolerance increased over time after heat hardening until 49 h after exposure when the experiment ended. On the other hand the expression of hsp70 messenger RNA reached a peak within the first 2 h and then sharply decreased after 6 h. Within 23 h hsp70 expression was back to control levels. 4Surprisingly, protein levels of Hsp70 followed thermotolerance and reached the highest levels 49 h after heat hardening. A significant positive association was found between thermotolerance and Hsp70 protein levels, but not with hsp70 mRNA levels. 5Our results support a strong correlation between Hsp70 expression levels and thermal resistance following a heat hardening treatment. They also show that gene and protein expression follow different dynamics, a difference that may be important for our understanding of the role of candidate genes in functional studies. [source]


Role of neuroimaging in promoting long-term recovery from ischemic stroke

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010
Rüdiger J. Seitz MD
Abstract Human ischemic stroke is an acute disorder followed by a recovery period which may be of varying duration and mechanism. Imaging has created a means to explore the stroke process in vivo, particularly its underlying pathophysiology and recovery mechanisms. Evidence from multicenter studies has shown that, in the acute phase, arterial recanalization and reperfusion of ischemic brain tissue are the most important determinants of recovery. This is followed by functional and structural changes in the perilesional tissue and in large-scale bihemispheric networks that continue with different dynamics for weeks to months. Proof-of-principle studies have revealed that the behavioral gains induced by rehabilitation are paralleled by changes in functional representations. This is supported by data from neuroimaging and electrophysiological studies early after stroke which have shown that dedicated training can induce changes in cerebral functional representations. Accordingly, there is clear evidence that neuroimaging has a significant potential for monitoring the hemodynamic, functional, and structural factors determining recovery from stroke. New imaging methods may provide relevant biomarkers for treatment decisions and therapeutic monitoring. By combining neuroimaging with electrophysiological measures, opportunities exist to develop neuroscience-based strategies in rehabilitation. J. Magn. Reson. Imaging 2010;32:756,772. © 2010 Wiley-Liss, Inc. [source]


AN EVALUATION OF THE AVAILABLE TECHNIQUES FOR ESTIMATING MISSING FECAL COLIFORM DATA,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004
Ashu Jain
ABSTRACT: This paper presents the findings of a study aimed at evaluating the available techniques for estimating missing fecal coliform (FC) data on a temporal basis. The techniques investigated include: linear and nonlinear regression analysis and interpolation functions, and the use of artificial neural networks (ANNs). In all, seven interpolation, two regression, and one ANN model structures were investigated. This paper also investigates the validity of a hypothesis that estimating missing FC data by developing different models using different data corresponding to different dynamics associated with different trends in the FC data may result in a better model performance. The FC data (counts/100 ml) derived from the North Fork of the Kentucky River in Kentucky were employed to calibrate and validate various models. The performance of various models was evaluated using a wide variety of standard statistical measures. The results obtained in this study are able to demonstrate that the ANNs can be preferred over the conventional techniques in estimating missing FC data in a watershed. The regression technique was not found suitable in estimating missing FC data on a temporal basis. Further, it has been found that it is possible to achieve a better model performance by first decomposing the whole data set into different categories corresponding to different dynamics and then developing separate models for separate categories rather than developing a single model for the composite data set. [source]


Dynamic advertising with spillovers: Cartel vs competitive fringe

OPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 6 2009
Luca Lambertini
Abstract A differential oligopoly game with advertising is investigated, where different dynamics occur between two groups of agents, the former playing a competitive Nash game and the latter cooperating as a cartel. Sufficient conditions for stability and a qualitative analysis of the profit ratio and social welfare at equilibrium are provided. A threshold value for the size of the competitive fringe is pointed out by a suitable numerical simulation. Copyright © 2009 John Wiley & Sons, Ltd. [source]