Modification of Polymyxin B1 by Water-Soluble Functional Copolymers of Vinyl Alcohol

Russian Journal of General Chemistry - The condensation of the peptide antibiotic Polymyxin В1 with the vinyl alcohol copolymers containing aldehyde groups was studied. The structure and...     

XO: An extended ONIOM method for accurate and efficient modeling of large systems

Calculation of large complex systems remains to be a great challenge, where there is always a trade‐off between accuracy and efficiency. Recently, we proposed the extended our own n‐layered integrated molecular orbital (ONIOM) method (XO) (Guo, Wu, Xu, Chem. Phys. Lett. 2010 , 498, 203) which surmounts some inherited limitations of the popular ONIOM method by introducing the inclusion‐exclusion principle used in the fragmentation methods. The present work sets up general guidelines for the construction of a good XO scheme. In particular, force‐error test is proposed to quantitatively validate the usefulness of an XO scheme, taking accuracy, efficiency and scalability all into account. Representative studies on zeolites, polypeptides and cyclodextrins have been carried out to demonstrate how to strive for high accuracy without sacrificing efficiency. As a natural extension, XO is applied to calculate the total energy, fully optimized geometry and vibrational spectra of the whole system, where ONIOM becomes inapplicable. © 2012 Wiley Periodicals, Inc.     

Detection of the spectra of multicharged ions with time resolution and the determination of the parameters of the hot component of the plasma in the case of the magnetic implosion of multiwire arrays

The dynamics of the hot component of the plasma of imploding multiwire arrays has been analyzed using the time behavior of the X-ray spectral lines of multicharge ions. The spectra of H- and He-like aluminum ions with nanosecond time resolution have been detected using electron-optical chronography in experiments on the implosion of multiwire arrays by mega-ampere currents. The simultaneous appearance of the resonance lines of H- and He-like ions implies that the hot plasma whose electron temperature is higher than 0.5 keV has existed on the axis before the implosion of the main mass of the liner. The further dynamics of the intensity of the lines is primarily attributed to an increase in the mass of the emitting plasma.     

Oil-loaded monolinolein-based particles with confined inverse discontinuous cubic structure (Fd3m)

In our recent work, we reported on the effect of varying temperature and solubilizing tetradecane (TC) on the structural transitions observed in dispersed particles based on the monolinolein (MLO)-water-TC system. At a given temperature, the addition of TC induces a transition of the internal structure from the bicontinuous cubic phase, Pn3m, to the reversed hexagonal, H2, and to the isotropic liquid phase (water-in-oil (W/O) microemulsions). Our present study focuses on the discovery of a Fd3m phase (reversed discontinuous micellar cubic), which is formed in the MLO-water-TC system at a specific TC/MLO weight ratio. It is situated between the H2 and the isotropic liquid phase (W/O microemulsion). Remarkably, it is not found in the absence of TC by increasing the temperature. The Fd3m structure was investigated in detail by means of small-angle X-ray scattering (SAXS), and cryogenic transmission electron microscopy (cryo-TEM). The present work proves that the structural transformation in the dispersed particles from H2 (hexosomes) to the W/O microemulsion system (emulsified microemulsion (EME)) is indirect and it occurs gradually via an emulsified intermediate phase. Specifically, in addition to the nanostructured aqueous dispersions described above, we present new TC-loaded aqueous dispersions with a confined intermediate phase, which is a discontinuous micellar cubic phase of the symmetry Fd3m. We denoted this type of emulsified particles as "micellar cubosomes".     

一种小型化频率综合器的设计

小型化是现代电子系统的一个重要的发展方向,频率综合器的小型化设计是射频系统小型化设计的重点之一。本文介绍了频率综合器小型化设计中的关键技术,难点以及解决的几种方法。     

Study of the properties and structure of polyimide and bilayer fluoropolyimide films after space exposure on the Mir space station

Results of examination of bilayer polyimide and fluorinated polyimide films after their exposure to outer space on the Mir space station are reported. The polyimide films were screened by quartz plates during exposure. An increase in the surface energy and the work of adhesion indicate substantial hydrophilization of the open surface, as well as slight hydrophilization of the screened film surface. A difference in values of the surface energy and work of adhesion depending on the orientation of a sample relative to the direction of motion of the space station indicates that the surface properties of the outer surface of the unscreened film became anisotropic in character, with the anisotropy axis being aligned with the direction of motion of the spacecraft. The fact that the outer surface of the film has acquired anisotropic properties is corroborated by the results of study of scanning electron microscopic images and polar plots of brightness. The hydrophilization of the films indicates an increase in the concentration of polar groups. In the space environment, the degradation of the fluoropolymer surface layer and its removal under high-vacuum conditions take place. For the quartz-shielded polyimide films, the surface energy and the work of adhesion remained practically the same as for the unexposed films. It was concluded that solar radiation (μ > 200 nm) does not cause a significant decline in the properties of the polyimide film.