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Zongpeng Wang, Yumin Hou
We investigate the absorption enhancement of an unstructured graphene sheet in a broad frequency range from terahertz (THz) to mid-infrared regime. Ultra-multiband graphene absorption enhancement is observed by integrating graphene in a metal-dielectric-graphene (MDG) sandwich structure for polarized waves. Multiple order Fabry-Perot (FP) resonances are demonstrated to be responsible for the multiband absorption. Furthermore, perfect absorption is realized by introducing the MDG structure on a metal reflector to suppress the transmission channel...
August 7, 2017: Optics Express
Alexander Toet
Despite of the ongoing interest in the fusion of multi-band images for surveillance applications and a steady stream of publications in this area, there is only a very small number of static registered multi-band test images (and a total lack of dynamic image sequences) publicly available for the development and evaluation of image fusion algorithms. To fill this gap, the TNO Multiband Image Collection provides intensified visual (390-700 nm), near-infrared (700-1000 nm), and longwave infrared (8-12 µm) nighttime imagery of different military and surveillance scenarios, showing different objects and targets (e...
December 2017: Data in Brief
Julia E Cohen-Gilbert, Lisa D Nickerson, Jennifer T Sneider, Emily N Oot, Anna M Seraikas, Michael L Rohan, Marisa M Silveri
The transition to college is associated with an increase in heavy episodic alcohol use, or binge drinking, during a time when the prefrontal cortex and prefrontal-limbic circuitry continue to mature. Traits associated with this immaturity, including impulsivity in emotional contexts, may contribute to risky and heavy episodic alcohol consumption. The current study used blood oxygen level dependent (BOLD) multiband functional magnetic resonance imaging (fMRI) to assess brain activation during a task that required participants to ignore background images with positive, negative, or neutral emotional valence while performing an inhibitory control task (Go-NoGo)...
2017: Frontiers in Psychology
Fei Chen, Dingchang Zheng, Yu Tsao
Vocoder simulation studies have suggested that the carrier signal type employed affects the intelligibility of vocoded speech. The present work further assessed how carrier signal type interacts with additional signal processing, namely, single-channel noise suppression and envelope dynamic range compression, in determining the intelligibility of vocoder simulations. In Experiment 1, Mandarin sentences that had been corrupted by speech spectrum-shaped noise (SSN) or two-talker babble (2TB) were processed by one of four single-channel noise-suppression algorithms before undergoing tone-vocoded (TV) or noise-vocoded (NV) processing...
September 2017: Journal of the Acoustical Society of America
J S Egerton, M J S Lowe, P Huthwaite, H V Halai
Finite element (FE) simulations are popular for studying propagation and scattering of ultrasonic waves in nondestructive evaluation. For a large number of degrees of freedom, time domain FE simulations are much more efficient than the equivalent frequency domain solution. However, unlike frequency domain simulations, time domain simulations are often poor at representing the speed and the attenuation of waves if the material is strongly damping or highly dispersive. Here, the authors demonstrate efficient and accurate representation of propagated and scattered waves, achieved by combining a set of time domain solutions that are obtained for a set of frequency ranges known as bands, such that, in combination, the authors' multiband solution accurately represents the whole wave spectrum...
September 2017: Journal of the Acoustical Society of America
E Baldini, A Mann, L Benfatto, E Cappelluti, A Acocella, V M Silkin, S V Eremeev, A B Kuzmenko, S Borroni, T Tan, X X Xi, F Zerbetto, R Merlin, F Carbone
In systems having an anisotropic electronic structure, such as the layered materials graphite, graphene, and cuprates, impulsive light excitation can coherently stimulate specific bosonic modes, with exotic consequences for the emergent electronic properties. Here we show that the population of E_{2g} phonons in the multiband superconductor MgB_{2} can be selectively enhanced by femtosecond laser pulses, leading to a transient control of the number of carriers in the σ-electronic subsystem. The nonequilibrium evolution of the material optical constants is followed in the spectral region sensitive to both the a- and c-axis plasma frequencies and modeled theoretically, revealing the details of the σ-π interband scattering mechanism in MgB_{2}...
September 1, 2017: Physical Review Letters
Xiaoyuan Yang, Jingkai Wang, Ridong Zhu
A new framelet-based random walks (RW) method is presented for synthetic aperture radar (SAR) image fusion, including SAR-visible images, SAR-infrared images and Multiband SAR images. In this method, we build a novel random walks model based on the statistical characteristics of framelet coefficients to fuse the high-frequency and low-frequency coefficients. This model converts the fusion problem to estimate the probability of each framelet coefficient being assigned each input image. Experimental results show that the proposed approach improves the contrast while preserves the edges simultaneously, and outperforms many traditional and state-of-the-art fusion techniques in both qualitative and quantitative analysis...
August 30, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Yuting Yang, Tao Xu, Yun Fei Xu, Zhi Hong Hang
Interface states in photonic crystals provide efficient approaches to control the flow of light. Photonic Zak phase determines the bulk band properties of photonic crystals, and, by assembling two photonic crystals with different bulk band properties together, deterministic interface states can be realized. By translating each unit cell of a photonic crystal by half the lattice constant, another photonic crystal with identical common gaps but a different Zak phase at each photonic band can be created. By assembling these two photonic crystals together, multiband waveguide can thus be easily created and then experimentally characterized...
August 15, 2017: Optics Letters
Jun Hua, Xinyuan Miao, Shruti Agarwal, Chetan Bettegowda, Alfredo Quiñones-Hinojosa, John Laterra, Peter C M Van Zijl, James J Pekar, Jay J Pillai
At present, presurgical functional mapping is the most prevalent clinical application of functional magnetic resonance imaging (fMRI). Signal dropouts and distortions caused by susceptibility effects in the current standard echo planar imaging (EPI)-based fMRI images are well-known problems and pose a major hurdle for the application of fMRI in several brain regions, many of which are related to language mapping in presurgical planning. Such artifacts are particularly problematic in patients with previous surgical resection cavities, craniotomy hardware, hemorrhage, and vascular malformation...
June 2017: Tomography: a Journal for Imaging Research
Sana Suri, Anya Topiwala, Nicola Filippini, Enikő Zsoldos, Abda Mahmood, Claire E Sexton, Archana Singh-Manoux, Mika Kivimäki, Clare E Mackay, Stephen Smith, Klaus P Ebmeier
Episodic and spatial memory are commonly impaired in ageing and Alzheimer's disease. Volumetric and task-based functional magnetic resonance imaging (fMRI) studies suggest a preferential involvement of the medial temporal lobe (MTL), particularly the hippocampus, in episodic and spatial memory processing. The present study examined how these two memory types were related in terms of their associated resting-state functional architecture. 3T multiband resting state fMRI scans from 497 participants (60-82 years old) of the cross-sectional Whitehall II Imaging sub-study were analysed using an unbiased, data-driven network-modelling technique (FSLNets)...
July 26, 2017: NeuroImage
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
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