Structural basis for the potential antitumour activity of DNA-interacting benzo[kl]xanthene lignans

The biological properties and possible pharmacological applications of benzo[kl]xanthene lignans, rare among natural products and synthetic compounds, are almost unexplored. In the present contribution, the possible interaction of six synthetic benzo[kl]xanthene lignans and the natural metabolite rufescidride with DNA has been investigated through a combined STD-NMR and molecular docking approach, paralleled by in vitro biological assays on their antiproliferative activity towards two different cancer cell lines: SW 480 and HepG2. Our data suggest that the benzo[kl]xanthene lignans are suitable lead compounds for the design of DNA selective ligands with potential antitumour properties.     

Double pulse quasi-collinear high harmonic generation scheme as a tool for X-ray laser plasma gain probing

We calculate the field distribution based on the vector diffraction theory for a superposition of spirally phase shifted radially polarized beams. Twisted longitudinally polarized field is found in the focal region. The total intensity as well as the polarization components rotates around the beam axis near the focus. Calculation of the Poynting vector at the focal plane shows that the electromagnetic energy is redistributed between different polarization components. Nonzero value of transverse components of the Poynting vector implies the transverse flow of the energy in the focal region.     

Ultrasound in gas-liquid systems: effects on solubility and mass transfer

The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas-liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas-liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing.     

Heavy ion–acoustic rogue waves in magnetized electron–positron multi-ion plasmas

Non-linear heavy ion-acoustic waves (HIAWs) are studied in a homogeneous magnetized four-component multi-ion plasma composed of inertial heavy negative ions, light positive ions, and inertia-less non-extensive electrons and positrons. The non-linear Schrödinger equation is derived in this model using the perturbation method. The criteria for modulational instability of HIAWs and the basic features of finite-amplitude heavy ion acoustic rogue waves (HIARWs) are investigated. The presence of the magnetic field was found to reduce the amplitude of HIARWs and enhances the stability. It is interesting to note that increasing positive ion mass causes decreases in the amplitude and width of rogue waves, which is opposite behaviour to that demonstrated in the previous study of these waves in an unmagnetized plasma. Furthermore, it is also shown that striking parameters, such as the non-extensive parameter, the positron number density, the electron number density, the electron temperature, and the magnetic field parameter, play an undeniable role on the stability of waves packets. The findings of the present investigation may be of wide relevance to some plasma environments, such as active galactic nuclei, pulsar magnetospheres, and other magnetic confinement systems.     

Sur un concept original : La catalyse triphasique et les echangeurs de cations

The condensation in triphase process of aqueous formaldehyde with aromatic alkenes dissolved in an organic solvent is possible in the presence of polystyrene sulfonic acid resin.     

Characterization of the molecular weight distribution of isotactic polypropylene by turbidity at the lower critical solution temperature (LCST)

The molecular weight distribution (MWD) of high-molecular-weight isotactic polypropylene is measured by a new method developed for polyethylene (PE) using the turbidity at the lower critical solution temperature (LCST). The attenuation of transmitted light h_i is measured at T_i as each fraction i is separated from the solution during a temperature increase ΔT_i. From the thermogram, the set of h_i (T_i), the MWD can be calculated through a relation M_i = f(T_i). The solvent chosen, a mixture of butane and 2-methylbutane, optimizes resolution and relatively rapid dissolution. Homogenization and absence of degradation are verified by different methods including calorimetry in solution. © 1992 John Wiley & Sons, Inc.     

Electrochemical intercalation and deintercalation of NaxMnO2 bronzes

Various Na_xMnO₂ bronzes have been electrochemically deintercalated. Na_0.40MnO₂ has a channel structure which is maintained for a large intercalation range (0.30 ≤ × ≤ 0.58). In order to explain the upper intercalation limit, an ordered sodium distribution between two types of Na⁺ sites is proposed. Na_0.70MnO₂ and α-NaMnO₂ have lamellar structures of P2 and 0′3 types. During intercalation the original P2 type is maintained for 0.45 ≤ × ≤ 0.85 while two reversible structural transitions are observed from α-NaMnO₂. A similar behavior occurs during the deintercalation of the high-temperature β-NaMnO₂ variety. In each case of the structural transition the double octahedral layers remain unchanged. Electronic localization (increased by Mn³⁺ Jahn—Teller effect) tends to trap the Na⁺ ions and therefore increases the relaxation time of the investigated materials.     

Spectres de vibration et conformation des diméthyl et diéthyl-2,2 stanna-2 dithia-1,3 cyclopentanes

An interpretation of the infrared and Raman spectra of 2,2-dialkyl-2-stanna-1,3-dithiacyclopentane R₂Sn(SCH₂)₂ (R = methyl, ethyl) is g assignments are compatible with a non-planar conformation of C_s symmetry for the Sn(CS)₂ skeleton.