Synthesis of N2-alkyl-8-oxo-7,8-dihydro-2'-deoxyguanosine derivatives and effects of these modifications on RNA duplex stability

N(2)-alkyl analogues of 8-oxo-7,8-dihydro-2'-deoxyguanosine (OG) were synthesized (alkyl = propyl, benzyl) via reductive amination of the protected OG nucleoside and incorporated into various positions of an RNA strand. Thermal stability studies of duplexes containing A or C opposite a single modified base revealed only moderate destabilization. Both OG as well as its N(2)-alkyl analogues can pair opposite A or C with nearly equal stability, potentially offering a new means of modulating RNA-protein interactions in the minor vs major grooves.     

Enhanced electrocatalytic performance of functionalized carbon nanotube electrodes for oxygen reduction in proton exchange membrane fuel cells

Although nitrogen doped CNTs (N-CNTs) are considered as a promising alternative to platinized carbon for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs), the origin of the enhanced ORR activity with N-CNTs is not clear at present. Among several plausible reasons, the exposure of edge plane and creation of impurity band/surface states near the Fermi level are considered as major causes behind the catalytic activity. However, CNTs without nitrogen doping are not known to catalyze the ORR. In this work, we study the ORR activity of functionalized carbon nanotubes with different functional groups, such as sulfonic acid and phosphonic acid, in order to understand the role of surface functionalities in catalyzing the reaction. Functionalized CNTs show significantly enhanced activity towards the ORR, while CNTs without such surface functional groups do not reveal any such special ORR activity. Linear sweep voltammetry experiments with different rotation rates show diffusion controlled limiting current values for functionalized CNTs, and the 'n' values derived from Koutecky-Levich plots are 3.3 and 1.7 for S-MWCNTs and P-MWCNTs, respectively. This work demonstrates the ORR activity of functionalized MWCNTs, which opens up new strategies for electrocatalyst design in PEMFCs.     

MHD effects on free convective flow over moving semi-infinite vertical cylinder with temperature oscillation

Numerical solutions of magnetodynamics(MHD) effects on the free convective flow of an incompressible viscous fluid past a moving semi-infinite vertical cylinder with temperature oscillation are presented.The dimensionless,unsteady,non-linear,and coupled governing partial differential equations are solved by using an implicit finite difference method of the Crank-Nicolson type.The velocity,temperature,and concentration profiles are studied for various parameters.The local skin-friction,the average skin-fr...     

The set of dynamically special points

We call a point ??dynamically special?? if it has a dynamical property, which no other point has. We prove that, for continuous self maps of the real line, all dynamically special points are in the closure of the union of the full orbits of periodic points, critical points and limits at infinity. We completely describe the set of dynamically special points of real polynomial functions. The following characterization for the set of special points is also obtained: A subset of ${\mathbb{R}}$ is the set of dynamically special points for some continuous self map of ${\mathbb{R}}$ if and only if it is closed.     

Substituent effect on azobenzene‐based liquid‐crystalline organophosphorus polymers

An Erratum has been published for this article in Journal of Polymer Science Part A: Polymer Chemistry (2003) 41(23) 3862 A new series of combined‐type, azobenzene‐based organophosphorus liquid‐crystalline polymers were synthesized, and their photoisomerization properties were studied. The prepared polymers contained azobenzene units as both the main‐chain and side‐chain mesogens. Various groups were substituted in the terminal of the side‐chain azobenzene mesogen, and the effects of the substituents were investigated. All the polymers were prepared at the ambient temperature by solution polycondensation with various 4‐substituted phenylazo‐4′‐phenyloxyhexylphosphorodichloridates and 4,4′‐bis(6‐hydroxyhexyloxy) azobenzene. The polymers were characterized with gel permeation chromatography, Fourier transform infrared, and ¹H, ¹³C, and ³¹P NMR spectroscopy. Thermogravimetric analysis revealed that all the polymers had high char yields. The liquid‐crystalline behavior of the polymers was examined with hot‐stage optical polarizing microscopy, and all the polymers showed liquid‐crystalline properties. The formation of a mesophase was confirmed by differential scanning calorimetry (DSC). The DSC data suggested that mesophase stability was better for electron‐withdrawing substituents than for halogens and unsubstituted ones. Ultraviolet irradiation studies indicated that the time taken for the completion of photoisomerization depended on the dipolar moment, size, and donor–acceptor characteristics of the terminal substituents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3188–3196, 2003     

Hybrid gold nanoparticles in molecular imaging and radiotherapy

Metallic nanoparticles, because of their size, chemical and physical properties, are particularly attractive as therapeutic probes in treating cancer. Central to any clinical advances in nanoparticulate based therapy will be to produce hybrid nanoparticles that can be targeted to vascular, extracellular or cell surface receptors. Development of hybrid nanoparticles that specifically target cancer vasculature has received considerable attention. Most cancers have leaky vasculature and the defective vascular architecture, created due to the rapid vascularization necessary to serve fast growing cancers, in combination with poor lymphatic drainage allows increased permeation and retention effects. The leaky vasculature, because of higher porosity and permeability, serve as natural high affinity targets to metallic nanoparticles. Another attractive approach toward the application of nanotechnology to nanomedicine is the utility of nanoparticles that display inherent therapeutic properties. For example radioactive gold nanoparticles present attractive prospects in therapy of cancer. The radioactive properties of Au-198 (β_max = 0.96 MeV; t_1/2 = 2.7 d) and Au-199 (β_max = 0.46 MeV; t_1/2 = 3.14 d) make them ideal candidates for use in radiotherapeutic applications. In addition, they both have imageable gamma emissions for dosimetry and pharmacokinetic studies and Au-199 can be made carrier-free by indirect methods. Gold nanoparticles are of interest for treatment of disease as they can deliver agents directly into cells and cellular components with a higher concentration of radioactivity, e.g. higher dose of radioactivity, to cancerous tumor cells.     

Periodic solutions of nonlinear wave equations with damping

A known existence theorem for doubly periodic solutions of nonlinear wave equations with linear damping is being proved in a direct manner by an approach which has been developed by the authors in [5, 6, 7] for hyperbolic problems, when the kernel of the underlying linear operator is infinite dimensional.