Noncovalent engineering of carbon nanotube surfaces by rigid,functional conjugated polymers

We report a new nonwrapping approach to noncovalent engineering of carbon nanotube surfaces by short, rigid functional conjugated polymers, poly(aryleneethynylene)s. Our technique not only enables the dissolution of various types of carbon nanotubes in organic solvents, which represents the first example of solubilization of carbon nanotubes via pi-stacking without polymer wrapping, but could also introduce numerous neutral and ionic functional groups onto the carbon nanotube surfaces.     

Imaging the neural circuitry and chemical control of aggressive motivation

Background  

With the advent of functional magnetic resonance imaging (fMRI) in awake animals it is possible to resolve patterns of neuronal activity across the entire brain with high spatial and temporal resolution. Synchronized changes in neuronal activity across multiple brain areas can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviors. To this end, fMRI in conscious rats combined with 3D computational analysis was used to identifying the putative distributed neural circuit involved in aggressive motivation and how this circuit is affected by drugs that block aggressive behavior.     

Triple corner reflector antenna and its performance in H-plane

An experimental investigation of a novel corner reflector antenna with improved performance is reported. The corner reflector antenna has been structurally modified by attaching two more reflector elements. The parameters such as the primary corner angle, position, width and angle of the secondary elements have significant effects on the H-plane radiation characteristics of the antenna. Certain symmetric configurations of this triple corner reflector (TCR) antenna provide sharp beams with a gain of the order of 3 dB over that of the conventional corner reflector (CR) antenna     

Multiple-magnetic field 139La NMR and density functional theory investigation of the solid lanthanum(III) halides

Results from a solid-state ¹³⁹La NMR spectroscopic investigation of the anhydrous lanthanum(III) halides (LaX₃; X=F, Cl, Br, I) at applied magnetic fields of 7.0, 9.4, 11.7, 14.1, and 17.6 T are presented and highlight the advantages of working at high applied magnetic field strengths. The ¹³⁹La quadrupolar coupling constants are found to range from 15.55 to 24.0 MHz for LaCl₃ and LaI₃, respectively. The lanthanum isotropic chemical shifts exhibit an inverse halogen dependence with values ranging from −135 ppm for LaF₃ to 700 ppm for LaI₃, which represents nearly half of the total lanthanum chemical shift range. The spans of the magnetic shielding tensors also vary widely, from 35 to 650 ppm for the solid LaF₃ through LaI₃. DFT calculations of the ¹³⁹La electric field gradient and magnetic shielding tensors have been performed and provide a qualitative interpretation of the trends observed experimentally.     

Computation of Dispersion in Microstrip Line with Anisotropic Substrate and Overlay

This paper presents an analysis of frequency dependent propagation characteristics of microstrip lines with anisotropic substrate and overlay. The method involves setting up of the Greens functions corresponding to the structure and formulating a dispersion relation in Fourier transform domain. The dispersion relation is constructed in a Galerkins procedure. Numerical results are also presented.     

Maximum norm stability of difference schemes for parabolic equations on overset nonmatching space-time grids

In this paper, theoretical results are described on the maximum norm stability and accuracy of finite difference discretizations of parabolic equations on overset nonmatching space-time grids. We consider parabolic equations containing a linear reaction term on a space-time domain which is decomposed into an overlapping collection of cylindrical subregions of the form , for . Each of the space-time domains are assumed to be independently grided (in parallel) according to the local geometry and space-time regularity of the solution, yielding space-time grids with mesh parameters and . In particular, the different space-time grids need not match on the regions of overlap, and the time steps can differ from one grid to the next. We discretize the parabolic equation on each local grid by employing an explicit or implicit -scheme in time and a finite difference scheme in space satisfying a discrete maximum principle. The local discretizations are coupled together, without the use of Lagrange multipliers, by requiring the boundary values on each space-time grid to match a suitable interpolation of the solution on adjacent grids. The resulting global discretization yields a large system of coupled equations which can be solved by a parallel Schwarz iterative procedure requiring some communication between adjacent subregions. Our analysis employs a contraction mapping argument.

Applications of the results are briefly indicated for reaction-diffusion equations with contractive terms and heterogeneous hyperbolic-parabolic approximations of parabolic equations.

     

Poly(4-vinylpyridine) catalyzed hydrolysis of methyl bromide to methanol and dimethyl ether

The hydrolysis of methyl bromide with neutral water is performed in the presence and absence of various amines in a batch reactor at different temperatures (50–125 °C). Screening of poly(4-vinylpyridine) as a potential reusable solid amine catalyst showed maximum efficiency. This significant enhancement in efficiency is due to the capture of HBr by solid PVP and remains phase-separated driving the reaction forward. The major advantage of this process is that the polymer can be easily regenerated and reused without loss of activity making it a very effective catalyst for the conversion of methyl halides to methanol and dimethyl ether.