High order kinoforms as a broadband achromatic diffractive optics for terahertz beams

We discuss thin optical structures that allow chromatic aberrations to be avoided in the THz domain. The paper contains the theoretical considerations, computer modeling and experimental evaluation of the high order kinoform diffractive elements in the THz range. According to the obtained results application of the high order kinoforms enables broadband operation in the THz range.

Modeling of the optical system illuminated by quasi-monochromatic spatially incoherent light: new numerical approach

This Letter presents a new method for modeling of complex optical setups illuminated by quasi monochromatic spatially incoherent light. The algorithm provides better performance and quality than other modeling methods both for isoplanatic and nonisoplanatic systems. The algorithm maintains energy relations, image orientation, and magnification of the system. Computer modeling and experimental results are presented.

The investigation on the mechanism of electrochemical hydrogen storage in sandwich nickel foam/palladium/carbon nanofibers electrodes

The kinetics of the process of reversible hydrogen sorption occurring in/on the nickel foam/palladium/carbon nanofibers (Ni/Pd/CNFs) electrodes is examined. It was shown that the hydrogen sorption/desorption properties for palladium can be altered after Pd layer is sandwiched between nickel foam and carbon nanofibers (CNF) layers. The layered Ni/Pd/CNFs electrodes were prepared by a two-step method consisting of chemical deposition of a very thin palladium layer on the Ni foam surface to form Ni/Pd electrodes followed by coating the Pd surface with the CNF layer by the CVD method. The process of hydrogen sorption/desorption into/from Ni/Pd as well as Ni/Pd/CNF electrodes was examined in alkaline electrolyte using the cyclic voltammetry method. The presence of CNF layer on the Pd surface exerts a great influence on the mechanism of the anodic desorption of hydrogen. A new anodic peak of hydrogen desorption revealed for Ni/Pd/CNF electrodes is ascribed to hydrogen storage in CNF phase. The CV measurements showed distinct differences between the rate of hydrogen release from the palladium and carbon phase.

Amphotericin B O-methyl oxime. Synthesis and biological properties

Synthesis and biological properties of amphotericin B O-methyl oxime are described. The presence of an intact hemiketal ring in the antibiotic molecule appeared to be essential for its biological activity.

The structure of vacidin A, an aromatic heptaene macrolide antibiotic. I. Complete assignment of the 1H NMR spectrum and geometry of the polyene chromophore

The constitution of vacidin A, a representative of the aromatic heptaene macrolide antibiotics was established on the basis of 13C and 1H-1H double quantum filtered correlated spectroscopy, rotating frame nuclear Overhauser effect spectroscopy, J-resolved 1H as well as 1H-13C correlation NMR spectra. Geometry of the polyene chromophore was determined as 22E,24E,26E,28Z,30Z,32E,34E.

Quantitative structure-activity relationships in amphotericin B derivatives

The quantitative structure-activity relationships studies of amphotericin B and its 16 semisynthetic derivatives obtained by modification at carboxyl and amino groups have been done. The results of five biological tests were subjected to principal component analysis, a numerical method useful in the investigation of large sets of data. For some compounds, also, interaction with lipidic vesicles was investigated by spectroscopic methods. The results obtained indicate that: (i) The presence of positively charged nitrogen atom (protonable or bearing fixed charge) is indispensable for biological activity and antibiotic-sterol interaction; (ii) The lack of free carboxyl group in the molecule favours the differentiation between cholesterol and ergosterol containing cells.

Amides of polyene macrolide aureofacin. Synthesis and biological properties

Synthesis and biological properties of a number of amides of polyene macrolide antibiotic aureofacin obtained in the reaction of the antibiotic with various glycine esters are described.