Formation and characterization of polymersomes made by a solvent injection method

In this article a solvent injection method is described for vesicle formation using poly(butadiene)‐ b‐poly(acrylic acid) diblock copolymers as the amphiphilic molecules. Vesicles composed of polymer bilayers are commonly referred to as polymersomes. Solvent injection is shown to be a rapid method for polymersome formation suitable to make large volumes of polymersome solution. The method can be manipulated to obtain a wide range of vesicle sizes depending on the polymer concentration and preparation conditions. Polymersome solutions in this study are characterized using dynamic light scattering (DLS), fluorescent microscopy, and electron microscopy. Polymersome sizes range from tens of nanometers to several microns. The membrane thickness of smaller polymersomes is found to lie between 14–20 nm. Larger polymersomes are found to have somewhat thicker membranes. The procedure involves the addition of polymers dissolved in an organic solvent to a stirred aqueous solution. The formation of polymersomes by this method is proposed to be governed by the limited mutual solubility of the two solvents and the simultaneous diffusion of solvent and water out of and in to initially formed organic solvent droplets. Copyright © 2007 John Wiley & Sons, Ltd.     

Fluorinated carbohydrates—X: The mass spectra of acetylated deoxyfluoro-D-glucitols

The deoxyfluoro-D-glucopyranoses with the fluorine substituent severally at positions 6, 4, 3 and 2 were converted into the corresponding deoxyfluoro-D-glucitol pentaacetates (I to IV) and their 1-deuterated analogues (V to VIII). The mass spectra of these derivatives were rationalised in terms of the position of the fluorine substituent on the carbon chain.     

Theory of resonance tunnel coupling of lossy dielectric waveguides

Physics Institute, Estonian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 8, pp. 970–975, August, 1990.     

Comparison of the high-aperture Bessel and Gaussian beams

The diffraction broadening of the high-aperture freely propagating (vector) Bessel and Gaussian beams is considered. The dependences of the degree of transverse concentration of light in such beams on their axial and radial coordinates are obtained. It is shown that if the initial degree of the transverse localization of total power of these beams is the same, the diffraction broadening of a Gaussian beam is smaller than that of a Bessel beam, and the only advantage of the latter is the specific radial distribution of the field amplitude.     

Structures, physical properties, and chemistry of layered oxychalcogenides and oxypnictides

A series of layered oxychalcogenide and oxypnictide solids is described that contain oxide layers separated by distinct layers, which contain the softer chalcogenide (S, Se, Te) or pnictide (P, As, Sb, Bi) anions. The relationships between the crystal structures adopted by these compounds are described, and the physical and chemical properties of these materials are related to the structures and the properties of the elements. The properties exhibited by the oxychalcogenide materials include semiconductor properties, for example, in LaOCuCh (Ch = chalcogenide) and derivatives, unusual magnetic properties exhibited by the class Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni), and redox properties exhibited by the materials Sr 2MnO 2Cu 2 m-0.5 S m+1 ( m = 1-3) and Sr 4Mn 3O 7.5Cu 2Ch 2 (Ch = S, Se). Recent results in the oxychalcogenide area are reviewed, and some new results on the intriguing series of compounds Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni) are reported. Oxypnictides have received less recent attention, but this is changing: a new frenzy of research is underway following the discovery of high-temperature superconductivity (>40 K) in derivatives of the layered oxyarsenide LaOFeAs. The early results in this exciting new area will be reviewed.     

Stabilization of resonance states by an asymptotic Coulomb potential

The capability of using stabilization method with the asymptotic Coulomb potential for accurate resonance state parameter calculations is investigated for the one-dimensional model problem with a single open channel. It is shown that the replacement of the potential box conditions by the quantization with asymptotic Coulomb potential does not yield the significant errors in energy and width of resonances if the additional mathematical conditions are correctly taken into account. Analytical results are confirmed by the numerical calculations.     

Cation deficient layered Ruddlesden-Popper-related oxysulfides La2LnMS2O5 (Ln=La, Y; M=Nb, Ta)

The structures of the new oxysulfide Ruddlesden-Popper phases La2LnMS2O5 (Ln=La, Y; M=Nb, Ta) are reported together with an iodide-containing variant: La3-xNb1+xS2O5I2x (0相似文献