521 research outputs found
Differential activation of lumbar and sacral motor pools during walking at different speeds and slopes
Organization of spinal motor output has become of interest for investigating differential activation of lumbar and sacral motor pools during locomotor tasks. Motor pools are associated with functional grouping of motoneurons of the lower limb muscles. Here we examined how the spatiotemporal organization of lumbar and sacral motor pool activity during walking is orchestrated with slope of terrain and speed of progression. Ten subjects walked on an instrumented treadmill at different slopes and imposed speeds. Kinetics, kinematics, and electromyography of 16 lower limb muscles were recorded. The spinal locomotor output was assessed by decomposing the coordinated muscle activation profiles into a small set of common factors and by mapping them onto the rostrocaudal location of the motoneuron pools. Our results show that lumbar and sacral motor pool activity depend on slope and speed. Compared with level walking, sacral motor pools decrease their activity at negative slopes and increase at positive slopes, whereas lumbar motor pools increase their engagement when both positive and negative slope increase. These findings are consistent with a differential involvement of the lumbar and the sacral motor pools in relation to changes in positive and negative center of body mass mechanical power production due to slope and speed.NEW & NOTEWORTHY In this study, the spatiotemporal maps of motoneuron activity in the spinal cord were assessed during walking at different slopes and speeds. We found differential involvement of lumbar and sacral motor pools in relation to changes in positive and negative center of body mass power production due to slope and speed. The results are consistent with recent findings about the specialization of neuronal networks located at different segments of the spinal cord for performing specific locomotor tasks
Bisphenol-A Exposure During Adolescence Leads to Enduring Alterations in Cognition and Dendritic Spine Density in Adult Male and Female Rats
We have previously demonstrated that adolescent exposure of rats to bisphenol-A (BPA), an environmental endocrine disrupter, increases anxiety, impairs spatial memory, and decreases dendritic spine density in the CA1 region of the hippocampus (CA1) and medial prefrontal cortex (mPFC) when measured in adolescence in both sexes. The present study examined whether the behavioral and morphological alterations following BPA exposure during adolescent development are maintained into adulthood. Male and female, adolescent rats received BPA, 40 ÎĽg/kg/bodyweight, or control treatments for one week. In adulthood, subjects were tested for anxiety and locomotor activity, spatial memory, non-spatial visual memory, and sucrose preference. Additionally, stress-induced serum corticosterone levels and dendritic spine density in the mPFC and CA1 were measured. BPA-treated males, but not females, had decreased arm visits on the elevated plus maze, but there was no effect on anxiety. Non-spatial memory, object recognition, was also decreased in BPA treated males, but not females. BPA exposure did not alter spatial memory, object placement, but decreased exploration during the tasks in both sexes. No significant group differences in sucrose preference or serum corticosterone levels in response to a stress challenge were found. However, BPA exposure, regardless of sex, significantly decreased spine density of both apical and basal dendrites on pyramidal cells in CA1 but had no effect in the mPFC. Current data are discussed in relation to BPA dependent changes, which were present during adolescence and did, or did not, endure into adulthood. Overall, adolescent BPA exposure, below the current reference safe daily limit set by the U.S.E.P.A., leads to alterations in some behaviors and neuronal morphology that endure into adulthood
Erraticity of Rapidity Gaps
The use of rapidity gaps is proposed as a measure of the spatial pattern of
an event. When the event multiplicity is low, the gaps between neighboring
particles carry far more information about an event than multiplicity spikes,
which may occur very rarely. Two moments of the gap distrubiton are suggested
for characterizing an event. The fluctuations of those moments from event to
event are then quantified by an entropy-like measure, which serves to describe
erraticity. We use ECOMB to simulate the exclusive rapidity distribution of
each event, from which the erraticity measures are calculated. The dependences
of those measures on the order of of the moments provide single-parameter
characterizations of erraticity.Comment: 10 pages LaTeX + 5 figures p
The model of particle production by strong external sources
Using some knowledge of multiplicity disributions for high energy reactions,
it is possible to propose a simple analytical model of particle production by
strong external sources. The model describes qualitatively most peculiar
properties of the distributions. The generating function of the distribution
varies so drastically as it can happen at phase transitions.Comment: 7 pages, no Figures, LATEX; Eq. (10) corrected, Eqs (25), (26) added,
ref [20] corrected; Pisma v Zhetf 84, n5 (2006
Critical Behavior of Hadronic Fluctuations and the Effect of Final-State Randomization
The critical behaviors of quark-hadron phase transition are explored by use
of the Ising model adapted for hadron production. Various measures involving
the fluctuations of the produced hadrons in bins of various sizes are examined
with the aim of quantifying the clustering properties that are universal
features of all critical phenomena. Some of the measures involve wavelet
analysis. Two of the measures are found to exhibit the canonical power-law
behavior near the critical temperature. The effect of final-state randomization
is studied by requiring the produced particles to take random walks in the
transverse plane. It is demonstrated that for the measures considered the
dependence on the randomization process is weak. Since temperature is not a
directly measurable variable, the average hadronic density of a portion of each
event is used as the control variable that is measurable. The event-to-event
fluctuations are taken into account in the study of the dependence of the
chosen measures on that control variable. Phenomenologically verifiable
critical behaviors are found and are proposed for use as a signature of
quark-hadron phase transition in relativistic heavy-ion collisions.Comment: 17 pages (Latex) + 24 figures (ps file), submitted to Phys. Rev.
Congenital tumors and nonimmune hydrops fetalis
Peer Reviewe
Universal behavior of multiplicity differences in quark-hadron phase transition
The scaling behavior of factorial moments of the differences in
multiplicities between well separated bins in heavy-ion collisions is proposed
as a probe of quark-hadron phase transition. The method takes into account some
of the physical features of nuclear collisions that cause some difficulty in
the application of the usual method. It is shown in the Ginzburg-Landau theory
that a numerical value of the scaling exponent can be determined
independent of the parameters in the problem. The universality of
characterizes quark-hadron phase transition, and can be tested directly by
appropriately analyzed data.Comment: 15 pages, including 4 figures (in epsf file), Latex, submitted to
Phys. Rev.
Modified Gravity on the Brane and Dark Energy
We analyze the dynamics of an AdS5 braneworld with matter fields when gravity
is allowed to deviate from the Einstein form on the brane. We consider exact
5-dimensional warped solutions which are associated with conformal bulk fields
of weight -4 and describe on the brane the following three dynamics: those of
inhomogeneous dust, of generalized dark radiation, and of homogeneous
polytropic dark energy. We show that, with modified gravity on the brane, the
existence of such dynamical geometries requires the presence of non-conformal
matter fields confined to the brane.Comment: Revised version published in Gen. Rel. Grav. Typos corrected, updated
reference and some remarks added for clarity. 11 pages, latex, no figure
Separating Agent-Functioning and Inter-Agent Coordination by Activated Modules: The DECOMAS Architecture
The embedding of self-organizing inter-agent processes in distributed
software applications enables the decentralized coordination system elements,
solely based on concerted, localized interactions. The separation and
encapsulation of the activities that are conceptually related to the
coordination, is a crucial concern for systematic development practices in
order to prepare the reuse and systematic integration of coordination processes
in software systems. Here, we discuss a programming model that is based on the
externalization of processes prescriptions and their embedding in Multi-Agent
Systems (MAS). One fundamental design concern for a corresponding execution
middleware is the minimal-invasive augmentation of the activities that affect
coordination. This design challenge is approached by the activation of agent
modules. Modules are converted to software elements that reason about and
modify their host agent. We discuss and formalize this extension within the
context of a generic coordination architecture and exemplify the proposed
programming model with the decentralized management of (web) service
infrastructures
- …