A theory of topological separation of linear and star-shaped polymers by two-dimensional chromatography

Topology influences the size of macromolecules, but polymers are usually distributed with respect to molar mass, which also results in the size distribution within a polymeric sample. Due to this fact size-exclusion chromatography (SEC) is not able to separate even moderately polydisperse polymers by topology; the same is also true for the adsorption chromatography (AC). The full separation by molar mass and topology is not possible by any single mode of chromatography. These problems can be solved by means of two-dimensional chromatography which combines SEC and AC mechanisms. A theory of interactive chromatography of linear and star-shaped ideal-chain polymers is used to analyze two-dimensional chromatographic separation of polydisperse linear and star polymers. Basing on this theory, we simulate 2D-chromatograms for model mixtures of polydisperse linear and star-shaped polymers of equal average molar mass, and demonstrate that 2D-separation of such polymers by topology is possible. A possibility to separate symmetric and very asymmetric stars by 2D-chromatography is predicted. The influence of the molar-mass heterogeneity, pore size and adsorption interaction parameter on the 2D chromatographic pattern is analysed, and the conditions for a good separation of linear and star polymers are formulated. The theoretical results are in a qualitative agreement with the experimental data, which have been reported previously by Gerber and Radke.     

Irradiation of synthetic garnet by heavy ions and α-decay of Cm

Garnet, A₃B₂X₃O₁₂, has a structure that can incorporate actinides. Hence, the susceptibility of the garnet structure to radiation damage has been investigated by comparing the results of self-radiation damage from α-decay of ²⁴⁴Cm and a 1 MeV Kr²⁺ ion irradiation. Gradual amorphization with increasing fluence was observed by X-ray diffraction analysis and in situ transmission electron microscopy. The critical dose, D_c, for an yttrium-aluminum garnet (Y₃Al₅O₁₂) doped with 3 wt.% ²⁴⁴Cm is calculated to be 0.4 displacements per atom (dpa). While the doses obtained by ion irradiation experiments of garnets with different compositions (Y_2.43Nd_0.57)(Al_4.43Si_0.44)O₁₂, (Ca_1.64Ce_0.41Nd_0.42La_0.18Pr_0.18Sm_0.14Gd_0.04)Zr_1.27Fe_3.71O₁₂, and (Ca_1.09Gd_1.23Ce_0.43)Sn_1.16Fe_3.84O₁₂, varied from 0.29 to 0.55 dpa at room temperature. The similarity in the amorphization dose at room temperature and critical temperature of the different garnet compositions suggest that the radiation response for the garnet structure is structurally constrained, rather than sensitive to composition, which is the case for the pyrochlore structure-type.     

Magnetically Controlled Carbonate Nanocomposite with Ciprofloxacin for Biofilm Eradication

Biofilms are the reason for a vast majority of chronic inflammation cases and most acute inflammation. The treatment of biofilms still is a complicated task due to the low efficiency of drug delivery and high resistivity of the involved bacteria to harmful factors. Here we describe a magnetically controlled nanocomposite with a stimuli-responsive release profile based on calcium carbonate and magnetite with an encapsulated antibiotic (ciprofloxacin) that can be used to solve this problem. The material magnetic properties allowed targeted delivery, accumulation, and penetration of the composite in the biofilm, as well as the rapid triggered release of the entrapped antibiotic. Under the influence of an RF magnetic field with a frequency of 210 kHz, the composite underwent a phase transition from vaterite into calcite and promoted the release of ciprofloxacin. The effectiveness of the composite was tested against formed biofilms of E. coli and S. aureus and showed a 71% reduction in E. coli biofilm biomass and an 85% reduction in S. aureus biofilms. The efficiency of the composite with entrapped ciprofloxacin was higher than for the free antibiotic in the same concentration, up to 72%. The developed composite is a promising material for the treatment of biofilm-associated inflammations.     

A model validation approach to texture recognition and inpainting

A new approach to texture recognition and inpainting problems is proposed. The approach is based on the robust model validation and state estimation techniques. The proposed solutions require the modeling of textures by using uncertain dynamical systems. We propose a new modeling method which is efficient in terms of computational and memory requirements. The main aspects of the modeling method include system identification and order reduction of marginally stable uncertain discrete-time systems. To demonstrate the results, both static-image textures and video textures (also known as dynamic textures) are considered.     

Rationally based model for evaluating the optimal refrigerant mass charge in refrigerating machines

A rationally based algorithm was proposed to evaluate the optimal mass charge into refrigerating machines. The calculated results indicate that the system performance is strongly related to the refrigerant mass charge. In the early stage of the refrigerant charge process, a sharp rise of COP is observed. The COP reaches an optimal value for a specified refrigerant charge and shows a slight drop for a further increase of refrigerant charge. Calculated results reveal similar trends to those of experimental data. The analysis of the study can well interpret the cycle transformation subject to refrigerant mass charge.     

A simple gas chromatography method for the determination of ethylcarbamate in spirits

Summary Ethylcarbamate is a toxic component of certain spirits. For its determination, the spirit is concentrated to one-fifth of its volume, extracted with ethylacetate and analysed by capillary gas chromatography (GC) with flame ionization detection (FID). The method saves time and material and has proved to be a reliable test in different laboratories. The ethylcarbamate concentrations in 170 samples of Swiss origin are presented. the mean values were 1.0 mg/l in cherry brandies, 1.5 mg/l in plum brandies and 0.4 mg/l in Williams pear brandies. Ethylcarbamate concentrations may increase during storage, especially under the influence of daylight.

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Eine einfache gaschromatographische Methode zur Bestimmung von Ethylcarbamat in Spirituosen

Zusammenfassung Ethylcarbamat ist ein cancerogener Inhaltsstoff von gewissen Spirituosen. Zu dessen Bestimmung wird die Probe auf 1/5 ihres Volumens eingeengt, mit Ethylacetat extrahiert und durch Capillar-GC mit FID nachgewiesen. Die Methode ist zeitund materialsparend und hat sich bei einem Vergleich mit mehreren Laboratorien als zuverlässig erwiesen. Die Ethylcarbamatgehalte von 170 Spirituosenproben aus der Innerschweiz werden angegeben. Dabei liegen die Mittelwerte für Kirschwasser bei 1,0 mg/l, für Zwetschgen- und Pflümliwasser bei 1,5 mg/1 und für Williamsbranntweine bei 0,4 mg/1. Die Ethylcarbamatgehalte von Spirituosen können bei der Lagerung stark zunehmen, dies vor allem unter dem Einfluß von Tageslicht.

     

A simple gas chromatography method for the determination of ethylcarbamate in spirits

Ethylcarbamate is a toxic component of certain spirits. For its determination, the spirit is concentrated to one-fifth of its volume, extracted with ethylacetate and analysed by capillary gas chromatography (GC) with flame ionization detection (FID). The method saves time and material and has proved to be a reliable test in different laboratories. The ethylcarbamate concentrations in 170 samples of Swiss origin are presented. The mean values were 1.0 mg/l in cherry brandies, 1.5 mg/l in plum brandies and 0.4 mg/l in Williams pear brandies. Ethylcarbamate concentrations may increase during storage, especially under the influence of daylight.     

Phonon emission from a discrete sine-Gordon breather

Phonon emission from a large-amplitude discrete sine-Gordon breather was studied numerically for a small degree of discreteness. In contrast to the case of highly discrete system investigated by Boesch and Peyrard (Phys. Rev. B 43 (1991) 8491), it was found that the resonance between the breather's oscillation and the phonons of the lower phonon band edge (κ=0) takes place for a small degree of discreteness.