Exploring the role of white matter connectivity in cortex maturation.

The maturation of the cortical gray matter (GM) and white matter (WM) are described as sequential processes following multiple, but distinct rules. However, neither the mechanisms driving brain maturation processes, nor the relationship between GM and WM maturation are well understood. Here we use connectomics and two MRI measures reflecting maturation related changes in cerebral microstructure, namely the Apparent Diffusion Coefficient (ADC) and the T1 relaxation time (T1), to study brain development. We report that the advancement of GM and WM maturation are inter-related and depend on the underlying brain connectivity architecture. Particularly, GM regions and their incident WM connections show corresponding maturation levels, which is also observed for GM regions connected through a WM tract. Based on these observations, we propose a simple computational model supporting a key role for the connectome in propagating maturation signals sequentially from external stimuli, through primary sensory structures to higher order functional cortices

Pulmonary macrophage and epithelial cells

Separate abstracts were prepared for the 41 papers presented at the conference. Abstracts of two papers have appeared in previous issues of Energy Research Abstracts. (HLW

White matter microstructural changes in short-term learning of a continuous visuomotor sequence

Efficient neural transmission is crucial for optimal brain function, yet the plastic potential of white matter (WM) has long been overlooked. Growing evidence now shows that modifications to axons and myelin occur not only as a result of long-term learning, but also after short training periods. Motor sequence learning (MSL), a common paradigm used to study neuroplasticity, occurs in overlapping learning stages and different neural circuits are involved in each stage. However, most studies investigating short-term WM plasticity have used a pre-post design, in which the temporal dynamics of changes across learning stages cannot be assessed. In this study, we used multiple magnetic resonance imaging (MRI) scans at 7 T to investigate changes in WM in a group learning a complex visuomotor sequence (LRN) and in a control group (SMP) performing a simple sequence, for five consecutive days. Consistent with behavioral results, where most improvements occurred between the two first days, structural changes in WM were observed only in the early phase of learning (d1-d2), and in overall learning (d1-d5). In LRNs, WM microstructure was altered in the tracts underlying the primary motor and sensorimotor cortices. Moreover, our structural findings in WM were related to changes in functional connectivity, assessed with resting-state functional MRI data in the same cohort, through analyses in regions of interest (ROIs). Significant changes in WM microstructure were found in a ROI underlying the right supplementary motor area. Together, our findings provide evidence for highly dynamic WM plasticity in the sensorimotor network during short-term MSL

From downbuilding to contractional reactivation of salt-sediment systems: insights from analog modeling.

This work studies salt-detached fold-and-thrust belts involving minibasins by means of physical analogue modeling. The experimental set up consist of a series of minibasins and diapirs built by downbuilding into a regular polygonal framework. The minibasins-diapir framework were then submitted to contraction, and for some examples accompanied by different rates of syncontractional sedimentation. We aimed at evaluating the influence of an initial salt basin geometry (i.e. equal thickness vs. along-strike tapered) on the development of the salt-sediment system, and how this influences the geometries and kinematics of fold-and-thrust belts. We also tested how these are influenced by different syncontractional sedimentation rates. Results show that major differences on the early salt structures occur during downbuilding as a result of original salt budget (i.e. from pillows to diapirs), with a positive correlation between amount of original salt and salt structure development. Initial contractional deformation is localized on the weaker salt bodies, favoring salt extrusion. Shortening is then transferred forwards once vertical salt feeders are welded (i.e. secondary welds), while basal (primary) welds are sheared, rolled or delaminated. Changes on structural styles occur abruptly along-strike as controlled by degree of development of the precontractional salt structures. Relatively low syncontractional sedimentation rate delays forward propagation of deformation and promotes minibasins tilting. With larger sedimentation rates, a thicker cover inhibits minibasins deformation and secondary welding and, promotes a more coherent mechanical beam detached on the basal weld. Our modeling is compared to natural fold-and-thrust belts such as the Zagros and the European Alps

Timed patterns: TCOZ to timed automata

Abstract. The integrated logic-based modeling language, Timed Communicating Object Z (TCOZ), is well suited for presenting complete and coherent requirement models for complex real-time systems. However, the challenge is how to verify the TCOZ models with tool support, especially for analyzing timing properties. Specialized graph-based modeling technique, Timed Automata (TA), has powerful mechanisms for designing real-time models using multiple clocks and has well developed automatic tool support. One weakness of TA is the lack of high level composable graphical patterns to support systematic designs for complex systems. The investigation of possible links between TCOZ and TA may benefit both techniques. For TCOZ, TA’s tool support can be reused to check timing properties. For TA, a set of composable graphical patterns can be defined based on the semantics of the TCOZ constructs, so that those patterns can be re-used in a generic way. This paper firstly defines the composable TA graphical patterns, and then presents sound transformation rules and a tool for projecting TCOZ specifications into TA. A case study of a railroad crossing system is demonstrated

Influence on preexisting salt diapirs during thrust wedge evolution and secondary welding: insights from analogue modeling

Salt lithologies are mechanically weaker than other sedimentary rocks. Salt horizons usually act as décollements and precursor salt bodies preferentially deform early during contraction, concentrate deformation, and impact the structural style and kinematics during mountain building. Focusing on shortened isolated-diapir provinces, our analog modeling program investigates the influence of two salt walls on folding and thrusting. High resolution topographic scans and particle image analysis show that the presence of precursor diapirs impacts the layer parallel shortening patterns and presumably the stress field at the onset of contraction. Shortening concentrates on diapirs, leading to roof arching, crestal extension and salt extrusion. This sequence of events occurs earlier on thinner salt- sediment sequences including diapirs having well-developed pedestals, particularly when proximal to the deformation front. Folds and thrusts nucleate at salt walls if they feature a well-developed pedestal. Further shortening results in secondary welding as evidenced by the collapse of uplifted roof domes, cessation of indentation and reverse faulting nucleated at the secondary welds. Meanwhile, and depending upon the processes occurring on the diapir closer to the backstop, the deformation of the distal salt wall is discontinuous. Our modeling results are compared with experimental works and natural examples from the Fars (Zagros Mountains)

Gravitational Lensing and f(R) theories in the Palatini approach

We investigate gravitational lensing in the Palatini approach to the f(R) extended theories of gravity. Starting from an exact solution of the f(R) field equations, which corresponds to the Schwarzschild-de Sitter metric and, on the basis of recent studies on this metric, we focus on some lensing observables, in order to evaluate the effects of the non linearity of the gravity Lagrangian. We give estimates for some astrophysical events, and show that these effects are tiny for galactic lenses, but become interesting for extragalactic ones.Comment: 7 Pages, RevTex, 1 eps figure; references added; revised to match the version accepted for publication in General Relativity and Gravitatio

Spatial gradients in the cosmological constant

It is possible that there may be differences in the fundamental physical parameters from one side of the observed universe to the other. I show that the cosmological constant is likely to be the most sensitive of the physical parameters to possible spatial variation, because a small variation in any of the other parameters produces a huge variation of the cosmological constant. It therefore provides a very powerful {\em indirect} evidence against spatial gradients or temporal variation in the other fundamental physical parameters, at least 40 orders of magnitude more powerful than direct experimental constraints. Moreover, a gradient may potentially appear in theories where the variability of the cosmological constant is connected to an anthropic selection mechanism, invoked to explain the smallness of this parameter. In the Hubble damping mechanism for anthropic selection, I calculate the possible gradient. While this mechanism demonstrates the existence of this effect, it is too small to be seen experimentally, except possibly if inflation happens around the Planck scale.Comment: 12 page

Studying the anisotropy of the gravitational wave stochastic background with LISA

A plethora of gravitational wave stochastic backgrounds populate the sensitivity window of the Laser Interferometer Space Antenna. We show that LISA can detect the anisotropy of the background corresponding to the multipole moments of order l=2 and 4. The signal-to-noise ratio generated by galactic white dwarf binary systems could be as high as 60 for 3 yrs of integration, and LISA could provide valuable information on the spatial distribution of a variety of galactic sources. We also show that the cross-correlation of the data sets from two interferometers could marginally lead to meaningful upper-limits on the degree of isotropy of the primordial gravitational wave background.Comment: 4 pages, uses RevTe