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Yoojin Lee, Tae Kim
PURPOSE: To quantitatively assess the hypertension-induced cerebrovascular alterations by measuring the dynamics of arterial spin labeling (ASL) signals. MATERIALS AND METHODS: The multiband Look-Locker ASL (MB LL-ASL) technique was evaluated in comparison to a single-band LL-ASL for three healthy subjects. Also, seven healthy subjects were scanned to determine the strength of the vascular crushing gradients applied to separate arterial from tissue ASL signal. With the optimized MB LL-ASL technique, multiple parameters, cerebral blood flow (CBF), transit times to artery (tA ), and capillary (tC ), delivery duration of labeled blood (τ), and arterial blood volume (CBVa ), were simultaneously quantified for age-matched eight control and eight hypertensive subjects with 259 msec of temporal resolution and 20 slices covering the whole-brain region at 3T...
July 10, 2017: Journal of Magnetic Resonance Imaging: JMRI
Wladimir Moya, Gabriel Jacome, ChangKyoo Yoo
In order to enhance in terms of accuracy and predict the modeling of the potential distribution of species, the integration of using principal components of environmental variables as input of maximum entropy (MaxEnt) has been proposed in this study. Principal components selected previously from the principal component analysis results performed in ArcGIS in the environmental variables was used as an input data of MaxEnt instead of raw data to model the potential distribution of red spiny lobster from the year 1997 to 2015 and for three different future scenarios 2020, 2050, and 2070...
July 2017: Ecology and Evolution
Alexander D Cohen, Dardo Tomasi, Ehsan Shokri-Kojori, Andrew S Nencka, Yang Wang
Functional connectivity density mapping (FCDM) is a newly developed data-driven technique that quantifies the number of local and global functional connections for each voxel in the brain. In this study, we evaluated reproducibility, sensitivity, and specificity of both local functional connectivity density (lFCD) and global functional connectivity density (gFCD). We compared these metrics using the human connectome project (HCP) compatible high-resolution (2 mm isotropic, TR = 0.8 s) multiband (MB), and more typical, lower resolution (3...
July 4, 2017: Brain Imaging and Behavior
G Pawlik, J Niczyj, A Noculak, W Radosz, A Podhorodecki
In this work, we report the results of theoretical modeling supported and confirmed by experimentally measured emission, emission decay curves, and power dependent emission spectra for sub 10 nm β-NaGdF4:Er(3+),Yb(3+) nanocrystals with different Yb(3+) content (0.5%-15%). For the theoretical analysis, we develop a stochastic Monte Carlo model which is based on two components: (i) formation of clusters composed of Er(3+) ion and Yb(3+) neighbors, which gives insight into the role of local parameters and (ii) a simplified kinetic model of excitation and relaxation phenomena in pairs of Er(3+)and Yb(3+) ions...
June 28, 2017: Journal of Chemical Physics
Wen Xu, Tae Kyung Lee, Byeong-Seok Moon, Donglei Zhou, Hongwei Song, Young-Jin Kim, Sang Kyu Kwak, Peng Chen, Dong-Hwan Kim
Lanthanide upconversion (UC) luminescent nanocrystals exhibit a uniquely sharp multiband emission over a broad spectral bandwidth covering the ultraviolet region to the near-infrared (NIR) region when subjected to NIR excitation, which is vital for multichannel optical communication using wavelength-division multiplexing to achieve high transmission rates. In this study, we experimentally and theoretically investigated the spectral and spatial characterization of a single NaYF4:Yb(3+),Tm(3+)(Yb(3+),Er(3+)) UC nanocrystal as a nanowaveguide...
July 6, 2017: Nanoscale
Jana Hutter, Anthony N Price, Lucilio Cordero-Grande, Shaihan Malik, Giulio Ferrazzi, Andreia Gaspar, Emer J Hughes, Daan Christiaens, Laura McCabe, Torben Schneider, Mary A Rutherford, Joseph V Hajnal
PURPOSE: To develop a purpose-built quiet echo planar imaging capability for fetal functional and diffusion scans, for which acoustic considerations often compromise efficiency and resolution as well as angular/temporal coverage. METHODS: The gradient waveforms in multiband-accelerated single-shot echo planar imaging sequences have been redesigned to minimize spectral content. This includes a sinusoidal read-out with a single fundamental frequency, a constant phase encoding gradient, overlapping smoothed CAIPIRINHA blips, and a novel strategy to merge the crushers in diffusion MRI...
June 26, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Molin Zhou, Xingxing Jiang, Yangwu Guo, Zheshuai Lin, Jiyong Yao, Yicheng Wu
By combining different nonlinear optical-active structural chromophores with transition metal Mn into a crystal structure, two novel quaternary metal chalcogenides Pb0.65Mn2.85Ga3S8 (1) and Pb0.72Mn2.84Ga2.95Se8 (2) were successfully synthesized. Compounds 1 and 2 are isostructural, and they represent a new structure type that crystallizes in the space group P6̅ (No. 174) in the hexagonal system. Their structures feature an interesting three-dimensional open-tunnel framework composed of bridged infinite chains with Pb(2+) cations filling in the biggest tunnels...
July 17, 2017: Inorganic Chemistry
Massimo Zanetti, Lorenzo Bruzzone
Variational models are known to work well for addressing image restoration/regularization problems. However, most of the methods proposed in the literature are defined for scalar inputs and are used on multiband images (such as RGB or multispectral imagery) by the composition of a simple band-wise processing. This involves suboptimal results and may introduce artifacts. Only in a few cases, variational models are extended to the case of vector-valued inputs. However, the known implementations are restricted to the first-order models, while the second-order models are never considered...
September 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Rui Xie, Xianrong Wan, Sheng Hong, Jianxin Yi
The performance of a passive radar network can be greatly improved by an optimal radar network structure. Generally, radar network structure optimization consists of two aspects, namely the placement of receivers in suitable places and selection of appropriate illuminators. The present study investigates issues concerning the joint optimization of receiver placement and illuminator selection for a passive radar network. Firstly, the required radar cross section (RCS) for target detection is chosen as the performance metric, and the joint optimization model boils down to the partition p-center problem (PPCP)...
June 14, 2017: Sensors
János K Asbóth, Andrea Alberti
We study the relation between the global topology of the Hofstadter butterfly of a multiband insulator and the topological invariants of the underlying Hamiltonian. The global topology of the butterfly, i.e., the displacement of the energy gaps as the magnetic field is varied by one flux quantum, is determined by the spectral flow of energy eigenstates crossing gaps as the field is tuned. We find that for each gap this spectral flow is equal to the topological invariant of the gap, i.e., the net number of edge modes traversing the gap...
May 26, 2017: Physical Review Letters
Sebastian Weingärtner, Steen Moeller, Sebastian Schmitter, Edward Auerbach, Peter Kellman, Chetan Shenoy, Mehmet Akçakaya
PURPOSE: To develop a saturation recovery myocardial T1 mapping method for the simultaneous multislice acquisition of three slices. METHODS: Saturation pulse-prepared heart rate independent inversion recovery (SAPPHIRE) T1 mapping was implemented with simultaneous multislice imaging using FLASH readouts for faster coverage of the myocardium. Controlled aliasing in parallel imaging (CAIPI) was used to achieve minimal noise amplification in three slices. Multiband reconstruction was performed using three linear reconstruction methods: Slice- and in-plane GRAPPA, CG-SENSE, and Tikhonov-regularized CG-SENSE...
August 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
M A Griffith, T O Puel, M A Continentino, G B Martins
A mean-field treatment is presented of a square lattice two-orbital-model for [Formula: see text] taking into account intra- and inter-orbital superconductivity. A rich phase diagram involving both types of superconductivity is presented as a function of the ratio between the couplings of electrons in the same and different orbitals ([Formula: see text]) and electron doping x. With the help of a quantity we call orbital-mixing ratio, denoted as [Formula: see text], the phase diagram is analyzed using a simple and intuitive picture based on how [Formula: see text] varies as electron doping increases...
June 2, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Luis Craco, Mukul S Laad, Stefano Leoni
Unusual metallic states involving breakdown of the standard Fermi-liquid picture of long-lived quasiparticles in well-defined band states emerge at low temperatures near correlation-driven Mott transitions. Prominent examples are ill-understood metallic states in d- and f-band compounds near Mott-like transitions. Finding of superconductivity in solid O2 on the border of an insulator-metal transition at high pressures close to 96 GPa is thus truly remarkable. Neither the insulator-metal transition nor superconductivity are understood satisfactorily...
June 1, 2017: Scientific Reports
Jana Hutter, J Donald Tournier, Anthony N Price, Lucilio Cordero-Grande, Emer J Hughes, Shaihan Malik, Johannes Steinweg, Matteo Bastiani, Stamatios N Sotiropoulos, Saad Jbabdi, Jesper Andersson, A David Edwards, Joseph V Hajnal
PURPOSE: Advanced diffusion magnetic resonance imaging benefits from collecting as much data as is feasible but is highly sensitive to subject motion and the risk of data loss increases with longer acquisition times. Our purpose was to create a maximally time-efficient and flexible diffusion acquisition capability with built-in robustness to partially acquired or interrupted scans. Our framework has been developed for the developing Human Connectome Project, but different application domains are equally possible...
May 30, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Gilad Liberman, Eddy Solomon, Michael Lustig, Lucio Frydman
PURPOSE: Spatio-temporal encoding (SPEN) experiments can deliver single-scan MR images without folding complications and with robustness to chemical shift and susceptibility artifacts. Further resolution improvements are shown to arise by relying on multiple receivers, to interpolate the sampled data along the low-bandwidth dimension. The ensuing multiple-sensor interpolation is akin to recently introduced SPEN interleaving procedures, albeit without requiring multiple shots. METHODS: By casting SPEN's spatial rasterization in k-space, it becomes evident that local k-data interpolations enabled by multiple receivers are akin to real-space interleaving of SPEN images...
May 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Toshihiko Aso, Guanhua Jiang, Shin-Ichi Urayama, Hidenao Fukuyama
Recent evidence has suggested that blood oxygenation level-dependent (BOLD) signals convey information about brain circulation via low frequency oscillation of systemic origin (sLFO) that travels through the vascular structure ("lag mapping"). Prompted by its promising application in both physiology and pathology, we examined this signal component using multiple approaches. A total of 30 healthy volunteers were recruited to perform two reproducibility experiments at 3 Tesla using multiband echo planar imaging...
2017: Frontiers in Neuroscience
Michele Fabrizio
We present a simple scheme to evaluate linear response functions including quantum fluctuation corrections on top of the Gutzwiller approximation. The method is derived for a generic multiband lattice Hamiltonian without any assumption about the dynamics of the variational correlation parameters that define the Gutzwiller wavefunction, and which thus behave as genuine dynamical degrees of freedom that add on those of the variational uncorrelated Slater determinant. We apply the method to the standard half-filled single-band Hubbard model...
February 28, 2017: Physical Review. B
Georgios Dimitrakopoulos, Ioannis Kakkos, Zhongxiang Dai, Julian Lim, Joshua deSouza, Anastasios Bezerianos, Yu Sun
Efficient classification of mental workload, an important issue in neuroscience, is limited so far to single task, while cross-task classification remains a challenge. Furthermore, network approaches have emerged as a promising direction for studying the complex organization of the brain, enabling easier interpretation of various mental states. In this study, using two mental tasks (N-back and mental arithmetic), we present a framework for cross- as well as within-task workload discrimination by utilizing multiband EEG cortical brain connectivity...
May 4, 2017: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Jorge Querol, José Miguel Tarongí, Giuseppe Forte, José Javier Gómez, Adriano Camps
MERITXELL is a ground-based multisensor instrument that includes a multiband dual-polarization radiometer, a GNSS reflectometer, and several optical sensors. Its main goals are twofold: to test data fusion techniques, and to develop Radio-Frequency Interference (RFI) detection, localization and mitigation techniques. The former is necessary to retrieve complementary data useful to develop geophysical models with improved accuracy, whereas the latter aims at solving one of the most important problems of microwave radiometry...
May 10, 2017: Sensors
Tun Cao, Yang Li, Chen-Wei Wei, Yi-Mei Qiu
We numerically demonstrate a multiband circular dichroism (CD) by tilting achiral metamaterials (MMs) composed of an elliptical nanoholes array (ENA) penetrating through metal/ phase-change material (PCM) /metal multilayer stack, with respect to the incident light. The CD spectrum can be actively tuned across a wide range from the near-infrared (NIR) to mid-infrared (MIR) regime by transiting the state of the PCM (Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>) from amorphous to crystalline...
May 1, 2017: Optics Express
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