Voxel selection in fMRI data analysis based on sparse representation

Multivariate pattern analysis approaches toward detection of brain regions from fMRI data have been gaining attention recently. In this study, we introduce an iterative sparse-representation-based algorithm for detection of voxels in functional MRI (fMRI) data with task relevant information. In each iteration of the algorithm, a linear programming problem is solved and a sparse weight vector is subsequently obtained. The final weight vector is the mean of those obtained in all iterations. The characteristics of our algorithm are as follows: 1) the weight vector (output) is sparse; 2) the magnitude of each entry of the weight vector represents the significance of its corresponding variable or feature in a classification or regression problem; and 3) due to the convergence of this algorithm, a stable weight vector is obtained. To demonstrate the validity of our algorithm and illustrate its application, we apply the algorithm to the Pittsburgh Brain Activity Interpretation Competition 2007 functional fMRI dataset for selecting the voxels, which are the most relevant to the tasks of the subjects. Based on this dataset, the aforementioned characteristics of our algorithm are analyzed, and a comparison between our method with the univariate general-linear-model-based statistical parametric mapping is performed. Using our method, a combination of voxels are selected based on the principle of effective/sparse representation of a task. Data analysis results in this paper show that this combination of voxels is suitable for decoding tasks and demonstrate the effectiveness of our method

Bis{μ-2,2′-[ethane-1,2-diylbis(nitrilo­methyl­idyne)]diphenolato}dinickel(II)

The asymmetric unit of the title compound, [Ni2(C16H14N2O2)2], contains an NiII cation which is coordinated by two imine N atoms and by two phenolate O atoms of the salen ligand {salen = N,N′-bis­(salicyl­idene)ethane-1,2-diamine or 2,2′-[ethane-1,2-diyl­bis(nitrilo­methyl­idyne)]diphenol}, leading to a distorted square-planar conformation. When a secondary Ni—O inter­action > 2.41 Å to the neighbouring phenolate O atom is considered, two mol­ecules are linked into a centrosymmetric dimer with an overall square-pyramidal coordination for the NiII cation. Weak π–π inter­actions with a shortest interplanar distance of 3.704 Å help to stabilize the crystal structure

A new species of Zhangixalus (Anura, Rhacophoridae) from Yunnan, China

We described herein Zhangixalus yunnanensis sp. nov., a new treefrog species from central and western Yunnan, China, which had previously been confused with Z. nigropunctatus, based on morphological and molecular evidence. Our phylogenetic analyses revealed that the new species is sister to the clade of Z. nigropunctatus and Z. melanoleucus with strong support (100% and 73% for BI and ML, respectively). Our morphological analysis suggested that Z. yunnanensis sp. nov. is distinctly different from all known congeners by the combination of the following morphological characters: black blotches on body flank and hind-limb, medium body size (SVL31.3–36.0 mm in males and 47.6–48.6 mm in females), head wider than long, iris yellowish-brown, dorsum uniformly green, vocal sac external, throat black, webbing greyish and fingers webbed one third and toes webbed half. Additionally, we revealed that the specimens ROM 38011 (Sa Pa, Vietnam) and VNMN 4099 (Son La, Vietnam) are neither Z. dorsoviridis nor Z. nigropunctatus, but probably represent one or two cryptic species of Zhangixalus pending further morphological and molecular data. Including the new species described herein, the genus Zhangixalus currently comprises 42 species, 30 of which are distributed in China with 11 species known from Yunnan. Amongst different zoogeographic regions in Yunnan, south-eastern Yunnan has the highest diversity of Zhangixalus, followed by western Yunnan and southern Yunnan. More studies are required to clarify the species diversity of this genus based on multiple lines of evidence (e.g. morphological and molecular data)

Particulate immersed boundary method for complex fluid-particle interaction problems with heat transfer

In our recent work (Zhang et al., 2015), a Particulate Immersed Boundary Method (PIBM) for simulating fluid-particle multiphase flow was proposed and assessed in both two- and three-dimensional applications. In this study, the PIBM was extended to solve thermal interaction problems between spherical particles and fluid. The Lattice Boltzmann Method (LBM) was adopted to solve the fluid flow and temperature fields, the PIBM was responsible for the no-slip velocity and temperature boundary conditions at the particle surface, and the kinematics and trajectory of the solid particles were evaluated by the Discrete Element Method (DEM). Four case studies were implemented to demonstrate the capability of the current coupling scheme. Firstly, numerical simulation of natural convection in a two-dimensional square cavity with an isothermal concentric annulus was carried out for verification purpose. The current results were found to have good agreement with previous references. Then, sedimentation of two-and three-dimensional isothermal particles in fluid was numerically studied, respectively. The instantaneous temperature distribution in the cavity was captured. The effect of the thermal buoyancy on particle behaviors was discussed. Finally, sedimentation of three-dimensional thermosensitive particles in fluid was numerically investigated. Our results revealed that the LBM-PIBM-DEM is a promising scheme for the solution of complex fluid-particle interaction problems with heat transfer.Peer ReviewedPostprint (author's final draft

PIBM: Particulate immersed boundary method for fluid-particle interaction problems

It is well known that the number of particles should be scaled up to enable industrial scale simulation. The calculations are more computationally intensive when the motion of the surrounding fluid is considered. Besides the advances in computer hardware and numerical algorithms, the coupling scheme also plays an important role on the computational efficiency. In this study, a particulate immersed boundary method (PIBM) for simulating the fluid–particle multiphase flow was presented and assessed in both two- and three-dimensional applications. The idea behind PIBM derives from the conventional momentum exchange-based Immersed Boundary Method (IBM) by treating each Lagrangian point as a solid particle. This treatment enables Lattice Boltzmann Method (LBM) to be coupled with fine particles residing within a particular grid cell. Compared with the conventional IBM, dozens of times speedup in two-dimensional simulation and hundreds of times in three-dimensional simulation can be expected under the same particle and mesh number. Numerical simulations of particle sedimentation in Newtonian flows were conducted based on a combined LBM–PIBM–Discrete Element Method (DEM) scheme, showing that the PIBM can capture the feature of particulate flows in fluid and is indeed a promising scheme for the solution of the fluid–particle interaction problems

Design of a dual-band radiation system for a complex magnetically insulated line oscillator

In this paper, a dual-band radiation system for a complex magnetically insulated line oscillator (MILO) is designed and investigated numerically. The radiation system comprises a coaxial plate-inserted mode converter, a power combiner and a conical horn antenna. The mode converter converts the coaxial TEM mode microwaves (1.775 GHz and 3.175 GHz) which are generated by the complex MILO into the coaxial TE11 mode microwaves, and then the coaxial TE11 mode microwaves are combined by the power combiner in a circular waveguide. Lastly, the microwaves are radiated by a conical horn antenna into the air. The gains of the dual-band radiation system are calculated to be 17.8 dB at 1.775 GHz and 18.9 dB at 3.175 GHz. The 3 dB beam widths are 20.5° in E-plane, 26.4° in H-plane at 1.775 GHz and 20.8° in E-plane, 15.1° in H-plane at 3.175 GHz. The power transmission efficiencies of the dual-band radiation system are 98.5% at 1.775 GHz and 95.7% at 3.175 GHz respectively. The power handling capacities of the dual-band radiation system are 4.2 GW at 1.775 GHz and 4.7 GW at 3.175 GHz, respectively