CFD simulation of methane dispersion and innovative methane management in underground mining faces

This study addresses methane dispersion in a mine tunnel with discrete methane sources and various methods to handle it. Air flow behavior and methane dispersion in the tunnel are simulated utilizing the computational fluid dynamics (CFD) approach. Various possible conditions which may occur in a mine tunnel are investigated. Simulation results indicate that methane dispersion inside the mine tunnel is influenced significantly by the number as well as location of the sources and quantity of methane released from each source. Furthermore, application of an innovative flow divider which comprises volumetric flow control and flow director, is investigated. It is found that by properly directing the ventilation flow to the location where methane is accumulating can reduce methane concentration below the safe level. In addition, it is noted that focusing the ventilation flow at a point is more effective as compared to dispersing it at several points. This study provides some new ideas for designing an “intelligent” underground mine ventilation system which can cost-effectively maintain methane concentration below the critical value.     

Routing vehicles to minimize fuel consumption

We consider a generalization of the capacitated vehicle routing problem known as the cumulative vehicle routing problem in the literature. Cumulative VRPs are known to be a simple model for fuel consumption in VRPs. We examine four variants of the problem, and give constant factor approximation algorithms. Our results are based on a well-known heuristic of partitioning the traveling salesman tours and the use of the averaging argument.     

A kernel machine-based fMRI physiological noise removal method

Functional magnetic resonance imaging (fMRI) technique with blood oxygenation level dependent (BOLD) contrast is a powerful tool for noninvasive mapping of brain function under task and resting states. The removal of cardiac- and respiration-induced physiological noise in fMRI data has been a significant challenge as fMRI studies seek to achieve higher spatial resolutions and characterize more subtle neuronal changes. The low temporal sampling rate of most multi-slice fMRI experiments often causes aliasing of physiological noise into the frequency range of BOLD activation signal. In addition, changes of heartbeat and respiration patterns also generate physiological fluctuations that have similar frequencies with BOLD activation. Most existing physiological noise-removal methods either place restrictive limitations on image acquisition or utilize filtering or regression based post-processing algorithms, which cannot distinguish the frequency-overlapping BOLD activation and the physiological noise. In this work, we address the challenge of physiological noise removal via the kernel machine technique, where a nonlinear kernel machine technique, kernel principal component analysis, is used with a specifically identified kernel function to differentiate BOLD signal from the physiological noise of the frequency. The proposed method was evaluated in human fMRI data acquired from multiple task-related and resting state fMRI experiments. A comparison study was also performed with an existing adaptive filtering method. The results indicate that the proposed method can effectively identify and reduce the physiological noise in fMRI data. The comparison study shows that the proposed method can provide comparable or better noise removal performance than the adaptive filtering approach.     

Perborate as novel fuel for enhanced performance of membraneless fuel cells

This paper presents the development of membraneless sodium perborate fuel cell using acid/alkaline electrolyte. In the acid/alkaline electrolyte, perborate works both as an oxidant as well as reductant. Sodium perborate affords hydrogen peroxide in aqueous medium. The cell converts the energy released by H₂O₂ decomposition with H⁺ and OH^? ions into electricity and produces water and oxygen. Such a novel design eliminates the need of a membrane, in which acid and alkaline electrolytes contact with each other. At room temperature, the laminar flow-based microfluidic membraneless fuel cell can reach a maximum power density of 34 mW/cm² with the molar ratio of [Perborate]/[NaOH]?=?1 as fuel and [Perborate]/[H₂SO₄]?=?2 as oxidant. The paper reports for the first time the use of sodium perborate as the oxidant and reductant. The developed fuel cell emits no CO₂, features no proton exchange membrane, inexpensive catalysts, and simple planar structure, which enables high design flexibility and easy integration of the microscale fuel cell into actual microfluidic systems and portable power applications.     

Cyclohexyl iodide promoted approach for coumarin analog synthesis using small scaffold

New chemical approaches were adopted for the synthesis of biologically important coumarins utilizing cyclohexane-1,3-dione derivatives as novel scaffold which were prepared from acetone and ethyl acrylate following our previous report. The stepwise strategies of aromatization, dehydrogenation, and demethylative cyclization were followed for coumarins synthesis from cyclohexane-1,3-dione derivatives. This work reports the first time cyclohexyl iodide was used for the demethylative cyclization reaction of $\upbeta , \upbeta $ -diaryl acrylates for 4-arylcoumarins synthesis. Graphical abstract      

Synthesis and characterization of layered perovskite-type oxides LnSr2MnFeO7 (Ln = La, Nd, Gd, and Dy)

Layered perovskite-type oxides LnSr₂MnFeO₇, with Ln?=?La, Nd, Gd, and Dy, have been synthesized by conventional solid-state reaction method. Rietveld refinement shows that all the phases were found to crystallize with tetragonal unit cell in the space group I4/mmm. The unit cell parameters a and c decrease monotonically with decreasing effective ionic radius of the lanthanide ion. The phases show insulating behavior with no anomalous features in the entire temperature range of 150–350 K and the electrical conduction occurs by Mott’s variable range hopping mechanism. The magnetic studies suggest that the phases are antiferromagnetic and the Weiss constant (θ) increases with decreasing ionic radius of lanthanide ion.     

A Symmetry‐Based Concise Formal Synthesis of Platencin,a Novel Lead against “Superbugs”

Quick access : A concise and efficient formal synthesis of platencin has been accomplished in nine steps from a commercially available starting material. The synthesis utilized only one protecting group. The base‐catalyzed Michael cyclization of precursor 1 afforded the key diketone 2 , which was converted into the desired core structure 4 via the radical intermediate 3 .

     

Two novel bis‐azomethines derived from quinoxaline‐2‐carbaldehyde

The Schiff base compounds N,N′‐bis[(E)‐quinoxalin‐2‐ylmethylidene]propane‐1,3‐diamine, C₂₁H₁₈N₆, (I), and N,N′‐bis[(E)‐quinoxalin‐2‐ylmethylidene]butane‐1,4‐diamine, C₂₂H₂₀N₆, (II), crystallize in the monoclinic crystal system. These molecules have crystallographically imposed symmetry. Compound (I) is located on a crystallographic twofold axis and (II) is located on an inversion centre. The molecular conformations of these crystal structures are stabilized by aromatic π–π stacking interactions.     

Combinatorics in affine flag varieties

The Littelmann path model gives a realization of the crystals of integrable representations of symmetrizable Kac–Moody Lie algebras. Recent work of Gaussent and Littelmann [S. Gaussent, P. Littelmann, LS galleries, the path model, and MV cycles, Duke Math. J. 127 (1) (2005) 35–88] and others [A. Braverman, D. Gaitsgory, Crystals via the affine Grassmannian, Duke Math. J. 107 (3) (2001) 561–575; S. Gaussent, G. Rousseau, Kac–Moody groups, hovels and Littelmann's paths, preprint, arXiv: math.GR/0703639, 2007] has demonstrated a connection between this model and the geometry of the loop Grassmanian. The alcove walk model is a version of the path model which is intimately connected to the combinatorics of the affine Hecke algebra. In this paper we define a refined alcove walk model which encodes the points of the affine flag variety. We show that this combinatorial indexing naturally indexes the cells in generalized Mirkovi?–Vilonen intersections.     

A diethyltartrate-based synthesis of both (−)- and (+)-arundic acid

A diethyltartrate-based synthesis of both enantiomers of the acute ischemic stroke therapeutic agent, arundic acid is presented. Separable diastereomers were obtained through the Johnson-Claisen rearrangement of the chiral vicinal diol based on the diethyltartrate skeleton and were converted separately into the two enantiomers of arundic acid.