Multiple Networks for Interhemispheric Integration in the Visual Brain: fMRI BOLD Response Increases with EEG Synchronization

2006.05.6-12, ISMRM 2006, International Society for Magnetic Resonance in Medicine, 14th Scientific Meeting, Seattle, Washington, USA. Book of abstracts ELECTRONIC POSTER DISCUSSION: The Future of BOLD? Resting State Signals and Multiple Modalities: Electronic Poste

fMRI responses in medial frontal cortex that depend on the temporal frequency of visual input.

Functional networks in the human brain have been investigated using electrophysiological methods (EEG/MEG, LFP, and MUA) and steady-state paradigms that apply periodic luminance or contrast modulation to drive cortical networks. We have used this approach with fMRI to characterize a cortical network driven by a checkerboard reversing at a fixed frequency. We found that the fMRI signals in voxels located in occipital cortex were increased by checkerboard reversal at frequencies ranging from 3 to 14 Hz. In contrast, the response of a cluster of voxels centered on basal medial frontal cortex depended strongly on the reversal frequency, consistently exhibiting a peak in the response for specific reversal frequencies between 3 and 5 Hz in each subject. The fMRI signals at the frontal voxels were positively correlated indicating a homogeneous cluster. Some of the occipital voxels were positively correlated to the frontal voxels apparently forming a large-scale functional network. Other occipital voxels were negatively correlated to the frontal voxels, suggesting a functionally distinct network. The results provide preliminary fMRI evidence that during visual stimulation, input frequency can be varied to engage different functional networks

Landslide monitoring by fixed-base terrestrial stereo-photogrammetry

Photogrammetry has been used since long to periodically control the evolution of landslides; however, true monitoring is reserved to robotic total stations and ground based InSAR systems, capable of high frequency, high accurate 24h/day response. This paper presents the first results of a fixed terrestrial stereo photogrammetric system developed to monitor shape changes of the scene. The system is made of two reflex cameras, each contained in a sealed box with a control computer that periodically acquires an image and send it to a host computer; once an image pair is received from the two cameras, the DSM of the scene is generated by image correlation and made available for archiving or analysis. The system has been installed and is being tested on the Mont de la Saxe landslide, where several monitoring system are active. Some instability of the camera attitude has been noticed and is corrected with an automated procedure. First comparisons with InSAR data show a good agreement

Structural and optical investigation of non-polar (1-100) GaN grown by the ammonothermal method

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Applied Physics 113, 203513 (2013) and may be found at https://doi.org/10.1063/1.4807581.We studied the structural and optical properties of state-of-the-art non-polar bulk GaN grown by the ammonothermal method. The investigated samples have an extremely low dislocation density (DD) of less than 5 × 104 cm−2, which results in very narrow high-resolution x-ray rocking curves. The a and c lattice parameters of these stress-free GaN samples were precisely determined by using an x-ray diffraction technique based on the modified Bond method. The obtained values are compared to the lattice parameters of free-standing GaN from different methods and sources. The observed differences are discussed in terms of free-electron concentrations, point defects, and DD. Micro Raman spectroscopy revealed a very narrow phonon linewidth and negligible built-in strain in accordance with the high-resolution x-ray diffraction data. The optical transitions were investigated by cathodoluminescence measurements. The analysis of the experimental data clearly demonstrates the excellent crystalline perfection of ammonothermal GaN material and its potential for fabrication of non-polar substrates for homoepitaxial growth of GaN based device structures

Ga2O3 polymorphs: Tailoring the epitaxial growth conditions

Gallium oxide is a wide bandgap n-type semiconductor highly interesting for optoelectronic applications (e.g., power electronics and solar blind UV photodetectors). Besides its most thermodynamically stable monoclinic β phase, Ga2O3 can crystallize in different polymorphs; among them the corundum α and the orthorhombic ϵ phases are the most promising ones. In this review we focus on the main aspects that promote the nucleation and stable growth of these Ga2O3 polymorphs. Particular emphasis is given to the ϵ phase since it is recently gaining increasing attention in the scientific community because of: (i) its higher lattice symmetry with respect to β-Ga2O3, which could favour the realization of heterostructures, (ii) the possibility to be grown on cheap sapphire substrates and (iii) its peculiar piezoelectric properties. While the growth of β-Ga2O3 is widely studied and understood, a thorough and comprehensive analysis of the chemical and physical aspects that allow for the stabilization of the metastable Ga2O3 phases with different synthesis methods is still missing. Therefore, the present review aims at filling this gap, by analysing the relevant growth parameters for several growth techniques (MOVPE, HVPE, mist-CVD, MBE, and PLD), highlighting similarities and differences, looking for a unified framework to understand the growth and nucleation of different Ga2O3 polymorphs. As a conclusion, we highlight practical guidelines for the deposition of the different Ga2O3 polymorphs with all the discussed thin film growth techniques

Abyssal Hill Segmentation: Quantitative Analysis of the East Pacific Rise Flanks 7°S-9°S

The recent RN Maurice Ewing EW9105 Hydrosweep survey of the East Pacific Rise (EPR) and adjacent flanks between 7°S and 9°S provides an excellent opportunity to explore the causal relationship between the ridge and the abyssal hills which form on its flanks. These data cover 100% of the flanking abyssal hills to 115 km on either side of the axis. We apply the methodology of Goff and Jordan (1988) for estimating statistical characteristics of abyssal hill morphology (rms height, characteristic lengths and widths, plan view aspect ratio, azimuthal orientation, and fractal dimension). Principal observations include the following: (I) the rms height of abyssal hill morphology is negatively correlated with the width of the 5- to 20-km-wide crestal high, consistent with the observations of Goff (1991) for northern EPR abyssal hill morphology; (2) the characteristic abyssal hill width displays no systematic variation with position relative to ridge segmentation within the EW9105 survey area, in contrast with observations of Goff (1991) for northern EPR abyssal hill morphology in which characteristic widths tend to be smallest al segment ends and largest toward the middle of segments; (3) abyssal hill rms heights and characteristic widths are very large just north of a counterclockwise rotating "nannoplate", suggesting that the overlap region is being pushed northward in response to microplate-style tectonics; and (4) within the 7°12'S-8°38'S segment, abyssal hill lineaments are generally parallel to the ridge axis, while south of this area, abyssal hill lineaments rotate with a larger "radius of curvature" than does the EPR axis approaching the EPR-Wilkes ridge-transform intersection

Low temperature superlattice in monoclinic PZT

TEM has shown that the strongly piezoelectric material Pb(Zr0.52Ti0.48)O3 separates into two phases at low temperatures. The majority phase is the monoclinic phase previously found by x-ray diffraction. The minority phase, with a nanoscale coherence length, is a slightly distorted variant of the first resulting from the anti-phase rotation of the oxygen octahedra about [111]. This work clears up a recent controversy about the origin of superlattice peaks in these materials, and supports recent theoretical results predicting the coexistence of ferroelectric and rotational instabilities.Comment: REVTeX4, 4 eps figures embedded. JPG version of figs. 2&4 is also include

Analysis of predictive thermodynamic models for estimation of polycyclic aromatic solid solubility in hot pressurized water

This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License.The ability of two thermodynamic approaches to predict the solubility of solid compounds in hot pressurized water is studied and compared. The Regular Solution Theory, based on the solubility parameter concept, and UNIFACbased models were applied to calculate the solute activity coefficient and then, solubility predictions were compared with experimental data reported in the literature. The analysis was carried out considering polycyclic aromatic hydrocarbons as model substances, i.e. substances which contain only the aromatic AC and ACH groups, and for which reliable pure physical properties such as melting point, fusion enthalpy and molar volume are available in the literature. The solubility values predicted with the UNIFAC-based models were considerably better than those obtained with the solubility parameter approach. Particularly, the modified Dortmund UNIFAC model presented an appropriate functionality of solubility with temperature, and the extension of this model to other type of aromatic compounds also provided a satisfactory prediction of solubility data.This work has been financed by project S2009-AGR- 1469 from the Comunidad Autónoma de Madrid (Spain) and CSD2007-00063 FUN-CFOOD (Programa CONSOLIDERINGENIO 2010) project.Peer Reviewe