Observation of the effects of radially sheared electric fields on the suppression of turbulent vortex structures and the associated transverse loss in GAMMA 10

Vortexlike turbulent structures in hot-ion mode plasmas with several keV are observed in the case with a radially produced weak shear of electric fields E(r). However, a strong E(r) shear formation due to a high ion-confining potential phi(c) production clears up these vortices together with plasma-confinement improvement and disappearance of both drift-wave and turbulencelike Fourier spectral signals. These findings are based on three-time progress in phi(c) in comparison to phi(c) attained 1992-2002. The significant advance of phi(c) is well extended in line with proposed potential-formation physics scalings.     

Rheological microscopy: local mechanical properties from microrheology

We demonstrate how tracer microrheology methods can be extended to study submicron scale variations in the viscoelastic response of soft materials; in particular, a semidilute solution of lambda-DNA. The polymer concentration is depleted near the surfaces of the tracer particles, within a distance comparable to the polymer correlation length. The rheology of this microscopic layer alters the tracers' motion and can be precisely quantified using one- and two-point microrheology. Interestingly, we found this mechanically distinct layer to be twice as thick as the layer of depleted concentration, likely due to solvent drainage through the locally perturbed polymer structure.     

Effect of Temperature and Ionic Concentration on Self-Assembled Films of Chicago Sky Blue

We employ a layer-by-layer adsorption technique for deposition on solid substrates of polyionic films of Chicago Sky Blue. Film growth was significant with the increasing number of layers. Photochemical properties of these films are investigated for different ionic concentrations. A significant blue shift is observed with the increasing ionic strength of the solution, suggesting the formation of aggregation. Temperature effect studies show some preferable reorientation of molecules in the film during cooling process. Most remarkable observation is that the absorption intensity is the highest for a particular degree of inclination. Deposition time is fixed at 15rain because adsorption kinetics results show saturation after 15 min.     

1,5-Benzothiazepine Derivatives: Green Synthesis,In Silico and In Vitro Evaluation as Anticancer Agents

Considering the importance of benzothiazepine pharmacophore, an attempt was carried out to synthesize novel 1,5-benzothiazepine derivatives using polyethylene glycol-400 (PEG-400)-mediated pathways. Initially, different chalcones were synthesized and then subjected to a cyclization step with benzothiazepine in the presence of bleaching clay and PEG-400. PEG-400-mediated synthesis resulted in a yield of more than 95% in less than an hour of reaction time. Synthesized compounds 2a–2j were investigated for their in vitro cytotoxic activity. Moreover, the same compounds were subjected to systematic in silico screening for the identification of target proteins such as human adenosine kinase, glycogen synthase kinase-3β, and human mitogen-activated protein kinase 1. The compounds showed promising results in cytotoxicity assays; among the tested compounds, 2c showed the most potent cytotoxic activity in the liver cancer cell line Hep G-2, with an IC₅₀ of 3.29 ± 0.15 µM, whereas the standard drug IC₅₀ was 4.68 ± 0.17 µM. In the prostate cancer cell line DU-145, the compounds displayed IC₅₀ ranges of 15.42 ± 0.16 to 41.34 ± 0.12 µM, while the standard drug had an IC₅₀ of 21.96 ± 0.15 µM. In terms of structural insights, the halogenated phenyl substitution on the second position of benzothiazepine was found to significantly improve the biological activity. This characteristic feature is supported by the binding patterns on the selected target proteins in docking simulations. In this study, 1,5-benzothiazepines have been identified as potential anticancer agents which can be further exploited for the development of more potent derivatives.     

Step and steady shear responses of nearly monodisperse highly entangled 1,4-polybutadiene solutions

Nonlinear relaxation dynamics of highly entangled solutions of high molecular weight 1,4-polybutadiene (PB) in a PB oligomer are studied in steady shear and step shear flows. Polymer entanglement densities vary in the range 14hN/N_e(J)⣴, allowing systematic investigation of entanglement effects on nonlinear rheological response. In agreement with previous steady shear studies using well entangled polystyrene solutions, a flow regime is found where both the steady-state shear stress and first normal stress difference remain constant or increase quite slowly with shear rate, leading to a plateau in the steady-state orientation angle. The magnitude of the average orientation angle in the plateau range is in accordance with predictions of a recent theory by Islam and Archer (2001). In step shear, the nonlinear relaxation modulus G(t,%) is approximately factorable into time-dependent G(t) and strain-dependent h(%) functions only at long times, t>5_k, where 5_k,O(F_d0). This finding is consistent with earlier observations for entangled polystyrene solutions; however the complex crossing pattern in G(t,%)h^-1(%) that precede factorability in the latter materials is not observed. For all but the most entangled sample, apparent shear damping functions h (%,t)=(G(t,%))/(G(t)) immediately following imposition of shear are in nearly quantitative accord with the damping function h_DEIA predicted by Doi-Edwards theory.     

Potential formation and high density plasma production on the tandem mirror GAMMA 10

GAMMA 10 experiments have advanced in high density experiments after the last EPS Workshop where we reported high density plasma production by using an ion cyclotron range of frequency heating at a high harmonic frequency and neutral beam injection in the central cell. Recently a high density plasma was obtained with much improved reproducibility than before and without degradation of diamagnetic signal. The high density plasma was attained by adjusting the spacing of the conducting plates installed in the anchor transition regions. Dependencies of particle confinement time, ion energy confinement time and plasma confining potential on plasma density were obtained for the first time in the high density region. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreus, Switzerland, June 23–24, 2002.     

Preclusion of nano scale self-assembly in block-selective non-aqueous solvents for rod–coil and coil–rod–coil macromolecular surfactants based on perylene tetracarboxylic diimide

Self-assembly of amphiphilic molecules ranging from simple surfactants to block copolymers in a solvent depends on one part of the molecule (one block in block copolymers) being soluble, and the other not. The aggregation of the insoluble segment in the block-selective solvent leads to the self assembly. In this paper, we describe a system of amphiphilic rod–coil and coil–rod–coil molecules, which do not show self assembly in block-selective non-aqueous solvents. We prepared rod–coil molecules based on hydrophilic propylene oxide/ethylene oxide copolymer (PO–EO copolymer) (Jeffamine®) as the flexible segment and photo-conducting large aromatic perylenediimide (PTCDI) as the rod. PO–EO copolymer was attached either to one side of PTCDI (MJ–PTCDI) or both sides (DJ–PTCDI). The former can be considered an inverse macromolecular surfactant, since the tail is hydrophilic and the head is hydrophobic. The DJ–PTCDI is a pseudo Gemini surfactant. Because of the presence of the chromophore, UV–Vis and fluorescent spectra could be used to study the self assembly of these amphiphilic rod coil polymers in solution. PTCDI forms π-interaction mediated aggregates in aqueous solution and these are H-stacked in MJ–PTCDI and J-stacked in DJ–PTCDI. Variable temperature UV and NMR spectra show that the assembly is stable over a large temperature range in water. The aggregates are also stable up to a pH of 12. However, when a non-aqueous solvent is used, no aggregation occurs. This is attributed to the “solvation” of the π-system of the PTCDI. With the addition of water, such solvation seems to be interrupted and aggregation occurs when water becomes a major component. We find that the mole percentage of the aggregates in acetone/water mixtures increases almost linearly with the concentration of water, providing a route to control the extent of aggregation of the chromophores. Due to the long, waxy PO–EO copolymer, MJ–PTCDI and DJ–PTCDI do not show liquid crystalline behavior or nanorod morphology, which were seen with short side chains. The optical microscopy of the bulk material shows aggregated crystals of PTCDI in the waxy matrix, showing that even in the presence of PO–EO copolymer, the molecular assembly of PTCDI takes place in the bulk. Secondary assembly was seen, in that upon ageing of the aqueous solutions, the drop cast films show that the spherical aggregates one-dimensionally coalesced into long fibers. Although UV–Vis spectra indicated no aggregation in non-aqueous solvents, drop-cast films of these solutions show needle-like aggregates and Lego-like assemblies.     

Modification of mechanical and thermal property of chitosan–starch blend films

Chitosan–starch blend films (thickness 0.2 mm) of different composition were prepared by casting and their mechanical properties were studied. To improve the properties of chitosan–starch films, glycerol and mustard oil of different composition were used. Chitosan–starch films, incorporated with glycerol and mustard oil, were further modified with monomer 2-hydroxyethyl methacrylate (HEMA) using gamma radiation. The modified films showed improvement in both tensile strength and elongation at break than the pure chitosan–starch films. Water uptake of the films reduced significantly than the pure chitosan–starch film. Thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) showed that the modified films experience less thermal degradation than the pure films. Scanning electron microscopy (SEM) and FTIR were used to investigate the morphology and molecular interaction of the blend film, respectively.     

Cascade cyclization of aryldiynes using iodine: synthesis of iodo-substituted benzo[b]naphtho[2,1-d]thiophene derivatives for dye-sensitized solar cells

A facile, efficient, and general synthetic method for iodo-substituted benzo[b]naphtho[2,1-d]thiophenes has been developed via a cascade cyclization of thioanisole-substituted aryldiynes using iodine. A new donor–π linker–acceptor (D–π–A) organic dye, G1, with the benzo[b]naphtho[2,1-d]thiophene moiety as an electron donor has been synthesized, and the performance of dye-sensitized solar cell based on G1 has been investigated.