Isolation of the minor and rare constituents from fruits of Peucedanum alsaticum L. using high-performance counter-current chromatography

A high-performance counter-current chromatography (HPCCC) method was applied for the first time for the preparative separation and purification of three rare compounds which occur as minor constituents in the fruits of Peucedanum alsaticum L.: 5-substituted coumarin notoptol and two dihydropyranochromones: divaricatol and ledebouriellol. A scale-up process from analytical to preparative in a very short time was developed. In order to purify a range of rare and minor compounds with different polarity two separate experiments were performed, one in reverse phase, the other in normal phase, using the same crude extract. A two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water (1:1:1:1) was developed. The components purified and collected were analyzed by high-performance liquid chromatography. The method yielded 0.7 mg of notoptol, 1.46 mg of ledebouriellol at purity of 99.5%, and 10 mg of mixtures of divaricatol, alsaticol and alsaticocoumarin, where divaricatol present 22% by peak area. These amounts were obtained from 1 g of the crude extract in a single run. This is the first time when minor notoptol, ledebouriellol, and divaricatol were isolated in a single run using HPCCC method and first time when these were identified in plant from Peucedanum genus.     

Improving AFM images with harmonic interference by spectral analysis

Atomic force microscopy (AFM) is one of the most sensitive tools for nanoscale imaging. As such, it is very sensitive to external noise sources that can affect the quality of collected data. The intensity of the disturbance depends on the noise source and the mode of operation. In some cases, the internal noise from commercial AFM controllers can be significant and difficult to remove. Thus, a new method based on spectrum analysis of the scanned images is proposed to reduce harmonic disturbances. The proposal is a post-processing method and can be applied at any time after measurements. This article includes a few methods of harmonic cancellation (e.g., median filtering, wavelet denoising, Savitzky-Golay smoothing) and compares their effectiveness. The proposed method, based on Fourier transform of the scanned images, was more productive than the other methods mentioned before. The presented data were achieved for images of conductive layers taken in a contact AFM mode.     

Contractivity of Leader type and fixed points in uniform spaces with generalized pseudodistances

Recently, Jachymski and Jó?wik proved that among various classes of contractions which are introduced and studied in the metric fixed point theory, the Leader contractions are greatest general contractions. In this article, we want to show how generalized pseudodistances in uniform spaces can be used to obtain new and general results of Leader type without complete graph assumptions about maps and without sequentially complete assumptions about spaces, which was not done in the previous publications on this subject. The definitions, results and methods presented here are new for maps in uniform and locally convex spaces and even in metric spaces. Examples showing a difference between our results and the well-known ones are given.     

Patterned colloid assembly by grafted photochromic polymer layers

Quartz surfaces and colloidal silica particles were derivatized with a poly(methyl methacrylate) copolymer containing spirobenzopyran (SP) photochromic molecules in the pendant groups at a concentration of 20 mol %. Two-photon near-IR excitation (approximately 780 nm) was then used to create chemically distinct patterns on the modified surfaces through a photochromic process of SP transformation to the zwitterionic merocyanine (MC) isomer. The derivatized colloids were approximately 10 times more likely to adsorb onto the photoswitched, MC regions. Surface coverage and adsorption kinetics have been compared to the mean-field model of irreversible monolayer adsorption.     

Photophysical effects between spirobenzopyran-methyl methacrylate-functionalized colloidal particles

Colloidal particles were derivatized with end-grafted polymethylmethacrylate polymer brushes containing varying concentrations of spirobenzopyran photochromic molecules. The polymers were grown from initiator-functionalized silica particles by an atom-transfer radical polymerization (ATRP). These core-shell colloids formed stable suspensions in toluene with the spirobenzopyran in its closed, nonpolar form. However, UV-induced photoswitching of the photochrome to its open, polar merocyanine isomer caused rapid aggregation. The nature of this colloidal stability transition was examined with respect to the spirobenzopyran content in the polymeric brush and solvent polarity. Turbidimetry, wettability studies, UV-vis spectroscopy, suspension rheology, SEM, and visual inspection were utilized to characterize the system photoswitchability. It was found that the system exhibiting the greatest transition in toluene was the copolymer brush composed of 20% spirobenzopyran and 80% methyl methacrylate.     

Anthralin: primary products of its redox reactions

One-electron reduction significantly enhances the ability of anthralin, 1, to act as a hydrogen atom donor. On annealing of an MTHF glass in which the radical anion of anthralin, 1*-, is generated radiolytically, this species decays mainly by loss of H* to give the anthralyl anion, 2- . On the other hand, radicals formed on radiolysis of matrices that are suitable for the generation of radical anions or cations are capable to abstract H* from anthralin to give the anthralyl radical, 2* . Both 2- and 2* are obtained simultaneously by mesolytic cleavage of the radical anion of the anthralin dimer. Contrary to general assumptions, the anthralyl radical is found to be much more reactive toward oxygen than the anion. All intermediates are characterized spectroscopically and by reference to quantum chemical calculations. Attempts to generate the radical cation of anthralin by X-irradiation of an Ar matrix containing anthralin led also to significant formation of its radical anion, i.e., anthralin acts apparently as an efficient electron trap in such experiments.     

Transition to chaos in the self-excited system with a cubic double well potential and parametric forcing

We examine the Melnikov criterion for a global homoclinic bifurcation and a possible transition to chaos in case of a single degree of freedom nonlinear oscillator with a symmetric double well nonlinear potential. The system was subjected simultaneously to parametric periodic forcing and self-excitation via negative damping term. Detailed numerical studies confirm the analytical predictions and show that transitions from regular to chaotic types of motion are often associated with increasing the energy of an oscillator and its escape from a single well.     

Radon-Nikodym derivatives of finitely additive interval measures taking values in a Banach space with basis

Let X be a Banach space with a Schauder basis { en }, and let Φ( I ) = Σ∞ n=1 en∫I fn(t)dt be a finitely additive interval measure on the unit interval [0, 1], where the integrals are taken in the sense of Henstock-Kurzweil. Necessary and sufficient conditions are given for Φ to be the indefinite integral of a Henstock-Kurzweil-Pettis (or Henstock, or variational Henstock) integrable function f : [0, 1] → X .     

Wetting transition in polyolefin blends studied by profiling techniques

Based on segregation data, determined with profiling techniques, we analyze surface phase diagram of binary liquid mixtures composed of random olefinic copolymers. Blends with extended‐ and small‐critical point wetting regimes are discussed. First observation of wetting transition is presented. Surface enrichment‐depletion duality, a phenomenon prerequisite to the 2^nd order wetting transition, is described.