Synthesis and Antitumor Activity of Heterocycles Related to Carbendazim

Three types of compounds were synthesized from carbendazim ( 1 ), a benzimidazole derivative (Scheme 1 ). They included a group of esters at N1 prepared by treating carbendazim with isocyanates bearing ester groups ( 2a , 2b , 2c ), carboxyalkyl‐1,2,3,4‐tetrahydro‐s‐triazino[1,2‐a]benzimidazole‐2,4‐dione esters ( 3a and 3b , 3d and 3c derived from 3a . The antitumor potencies of the N1 esters were in the range of 7 to 40 μM, which compares favorably with carbendazim, but their water solubilities were low. The s‐triazine derivatives showed activity against pancreatic tumor cells, and one of them ( 3b ) was active in mice, but they were not effective against other tumor types. Treatment of carbendazim with 3‐bromopropionyl chloride produced 1‐methoxycarbonyl‐4‐oxo‐1,2,3,4‐tetrahydropyrimido[1,2‐a]benzimidazole ( 4 ), which gave 1‐(3‐aminopropionyl)benzimidazole 2‐methylcarbamates, substituted on the amino nitrogen ( 5a , 5b , and 5d ), when treated with amines. These products showed some antitumor activity in cell cultures, and an ethoxy derivative ( 5c ), obtained by treating 1‐methoxycarbonyl‐4‐oxo‐1,2,3,4‐tetrahydropyrimido[1,2‐a]benzimidazole with sodium ethoxide, was active in the 67–150 μM range. Some of the new compounds had good water solubility. Carbendazim kills tumor cells by inhibiting tubulin; however, s‐triazine 3b , which differs from it in size and functional groups, does not act by this mechanism.     

A displaced-line velocity diagnostic and its application in a visualization engine

A technique for measuring three-dimensional velocity by imaging the displacement of a marked fluid line is described, together with its use in an automotive visualization engine. In a flow seeded with 2–3 μ phosphorescing particles, a line is excited by a UV laser beam, deformed by the local velocity field, and detected by stereo low-light-level video cameras. The derivation of velocity from digitized images is discussed and capabilities of the diagnostic are assessed. Some image data taken in the engine are shown and quantitative two-component velocity plots along the line are presented.     

Polymeric cross-linked surface treatments for controlling block copolymer orientation in thin films

The orientation of cylinder-forming poly(styrene-block-methyl methacrylate) [P(S-b-MMA)] was investigated on two sets of polymeric surface treatments: 10 para-substituted polystyrene derivatives with <10 mol % poly(4-vinylbenzyl azide) and a series of poly(styrene-random-4-vinylbenzyl azide) [P(S-r-VBzAz)] copolymers with 5-100 mol % poly(4-vinylbenzyl azide). The copolymers were spin-coated to form thin films and then cross-linked by heating. The resulting films exhibited a range of surface tensions from 21 to 45 dyn/cm. Perpendicular orientation of P(S-b-MMA) cylinders was achieved with poly(p-bromostyrene) and all the [P(S-r-VBzAz)] copolymer surface treatments, most notably the homopolymer of poly(4-vinylbenzyl azide). Films made from these simple copolymers are as effective as random terpolymer alignment layers commonly made from both block monomers and a cross-linkable monomer.     

Nanoscale mixing of soft solids

Assessing the state of mixing on the molecular scale in soft solids is challenging. Concentrated solutions of micelles formed by self-assembly of polystyrene-block-poly(ethylene-alt-propylene) (PS-PEP) diblock copolymers in squalane (C(30)H(62)) adopt a body-centered cubic (bcc) lattice, with glassy PS cores. Utilizing small-angle neutron scattering (SANS) and isotopic labeling ((1)H and (2)H (D) polystyrene blocks) in a contrast-matching solvent (a mixture of squalane and perdeuterated squalane), we demonstrate quantitatively the remarkable fact that a commercial mixer can create completely random mixtures of micelles with either normal, PS(H), or deuterium-labeled, PS(D), cores on a well-defined bcc lattice. The resulting SANS intensity is quantitatively modeled by the form factor of a single spherical core. These results demonstrate both the possibility of achieving complete nanoscale mixing in a soft solid and the use of SANS to quantify the randomness.     

Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film

La_0.67Ba_0.33MnO₃ (LBMO) thin film is deposited on a 36.7°C SrTiO₃ bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance with the increase in temperature is due to enhanced spin-flip scattering process.     

Yang-Mills and Dirac fields in a bag,constraints and reduction

The structure of the constraint set in the Yang-Mills-Dirac theory in a contractible bounded domain is analysed under the bag boundary conditions. The gauge symmetry group is identified, and it is proved that its action on the phase space is proper and admits slices. The reduced phase space is shown to be the union of symplectic manifolds, each of which corresponds to a definite mode of symmetry breaking.Research partially supported by NSERC Research Grant SAP0008091.Research partially supported by DFG Grant Schw. 485/2-1.Research partially supported by NSERC Research Grant OGP0042416.     

Heteroclinic solutions of a van der Waals model with indefinite nonlocal interactions

We construct heteroclinic the global minimizers of a nonlocal free energy functional that van der Waals derived in 1893. We study the case where the nonlocality satisfies only a weakened type of ellipticity, which precludes the use of comparison methods. In the interesting case when the local part of the energy is nonconvex, we construct a classical the global minimizer by studying a relaxed functional corresponding to the convexification of the local part and exclude the possibility of minimizers of the relaxed functional having rapid oscillations. We also construct examples where the global minimizer is not monotonic.     

Testing experimental analysis techniques for liquid crystals using computer simulation

Computer simulation has been used widely over the last two decades to investigate the phase behaviour and physical properties of liquid crystal systems. Here we review studies in which simulations have been used to calculate information on the physical properties of liquid crystals in a pseudo-experimental way. We concentrate on the calculation of 'experimental data' from computer simulations, from which we can extract information on the structure and dynamics of the nematic and smectic A phases. Where relevant, these are compared with both existing theoretical and experimental results. In particular, routes between the raw experimental data and physical parameters such as the orientational order parameter are highlighted and their effectiveness investigated.