Correlation functions for inhomogeneous magnetic field in random media with application to a dense random pack of spheres

In porous media subject to applied magnetic field, the internal field arises out of susceptibility contrast of the constituents. We have examined the spatial inhomogeneity of the internal fields in a random pack of spheres using numerical computation. We find that the pair-correlation function of the internal field (K2) is a close approximation to the structure factor of the material, thus K2 can be used to characterize pore geometry. The magnetic length scale LambdaM exhibited in K2 is shown to be related to the fluid transport in the medium.     

Biomolecule-based switching devices that respond inversely to thermal stimuli

We demonstrate a molecular switch, on the basis of the characteristic properties of DNA and RNA, which indicates a completely inverted response to thermal stimuli using the transition between right- and left-handed helices. We designed a system using aminopurine (Ap), which can convert the pi-stack information of the transition from right-handed to left-handed DNA (B-Z transition) and RNA (A-Z transition) into an output giving a fluorescent signal. These two biomolecular devices together serve as "right-left" or "off-on" switches. When the temperature is changed from low to high, the RNA device changes from the off to on signal; however, the DNA device changes from on to off. The response of these RNA and DNA based devices against thermal stimulus was completely reversible.     

Molecular dynamics simulation study on a monolayer of half [2]rotaxane self-assembled on Au(111)

The self-assembled monolayer (SAM) structure of the tetrathiafulvalene-side half of the Stoddart-Heath type [2]rotaxane on Au(111) surface was investigated using molecular dynamics (MD) simulations. We find that the orientation of the cyclobis(paraquat-p-phenylene) (CBPQT) ring depends dramatically on the coverage, changing in order to obtain highly packed SAMs. The ring lies with its large hollow parallel to the surface at lower coverage (up to one CBPQT per 27 surface Au atoms with a footprint of 1.9 nm(2); 1/27) when free space is available around it, but as the coverage increases (up to one CBPQT per 12 surface Au atoms with a footprint of 0.9 nm(2); 1/12), it tilts completely around its axis and lies with its smaller side (paraquat or phenyl ring) parallel to the surface to accommodate the reduced area available. We find that the best packing densities correspond to one CBPQT per 12-18 surface Au atoms (1/18-1/12) with footprints in the range between 0.9 nm(2) and 1.3 nm(2).     

Pyrazolidine derivatives with heteroaryl urea as dipeptidyl peptidase IV inhibitors

In the continuation of efforts to modify the structure of our novel DP-IV inhibitors, a series of pyrazolidine derivatives with heteroaryl urea was synthesized and evaluated for their ability to inhibit dipeptidyl peptidase IV (DP-IV).     

Hadron masses in medium and neutron star properties

We investigate the properties of the neutron star with relativistic mean-field models. We incorporate in the quantum hadrodynamics and in the quark-meson coupling models a possible reduction of meson masses in nuclear matter. The equation of state for neutron star matter is obtained and is employed in Oppenheimer-Volkov equation to extract the maximum mass of the stable neutron star. We find that the equation of state, the composition and the properties of the neutron stars are sensitive to the values of the meson masses in medium.     

Idesolide: a new spiro compound from Idesia polycarpa

[structure: see text]. Idesolide, a new spiro compound possessing tetrahydrobenzodioxole structure, was isolated from the fruits of Idesia polycarpa Maxim. Its structure was established by NMR and MS spectroscopic analysis with single-crystal X-ray experiments. Idesolide significantly reduced nitric oxide production induced by lipopolysaccharide in BV2 microglial cells.     

An anionic strategy for three- and four-component coupling reactions leading to ketone frameworks based on vinylogous conversion of dilithio ketone alpha,beta-dianions

[reaction: see text] Ketone alpha,delta-dianions are generated by vinylogous extension of ketone alpha,beta-dianions with alkenes such as vinylarenes, vinylsilanes, and vinyl sulfides, which then undergo reactions at the delta and alpha positions with different electrophiles, creating ketone frameworks. This work represents a cascade-type anion method that achieved three- and four-carbon component assembly reactions leading to ketones.     

Quencher-free, end-stacking oligonucleotides for probing single-base mismatches in DNA

[reaction: see text] Fluorescence can be quenched through PET from the fluorophore to neighboring C, T, and G bases, but not to the A moiety. The hairpin stem stability arising from pi-stacking and the PET between the pyrene-labeled 2'-deoxynucleotide units and their neighboring bases are the two main factors that affect the operation of these novel fluorescent oligonucleotides.     

An efficient cell separation system using 3D-asymmetric microelectrodes

An efficient 3D-asymmetric microelectrode system for high-throughput was designed and fabricated to enhance sorting sensitivities to the dielectric properties-size, morphology, conductivity, and permittivity-of living cells. The principle of the present system is based on the use of the relative strengths of negative dielectrophoretic and drag forces, as in a conventional 3D-microelectrode system. Whereas the typical 3D-microelectrode system has a constant electric field magnitude due to the constant width of the microelectrodes and a fixed gap between face-to-face microelectrodes, the present 3D-asymmetric microelectrode system has electric fields of continuously varying magnitudes along the transverse direction of a channel owing to the changing widths of the electrodes in the half-circular shaped cross section of the microchannel. Thus, varying dielectric forces are generated, leading to increased sorting sensitivity through differentially induced forces to definitely distinct cell types. Numerical analysis verified the improved sensitivity of the present system for sorting living cells. The feasibility of using the newly fabricated system under experimental conditions was tested by demonstrating that a mixed population of mouse P19 embryonic carcinoma (EC) and red blood cells (RBCs) was effectively sorted to different wells depending on their respective relative physical properties.     

In situ one-pot synthesis of 1-dimensional transition metal oxide nanocrystals

One-dimensional colloidal metal oxide nanocrystals are of great importance in materials chemistry, but reports on these materials are rare due to lack of well-defined synthetic protocols. In this paper, we present a general and highly effective one-pot synthetic protocol to produce 1-dimensional nanostructures of transition metal oxide (e.g., W(18)O(49), TiO(2), Mn(3)O(4), and V(2)O(5)) through thermally induced crystal growth processes from a mixture of metal chloride and surfactants.