Thermal transformation of polyacrylonitrile deposited on SBA-15 type silica

Thermogravimetry, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the studying of thermally induced structural changes of polyacrylonitrile (PAN) deposited on the surface of SBA-15 type mesoporous silica. Polymer was introduced onto the support by the precipitation polymerization of acrylonitrile in aqueous suspension of SBA-15. Low temperature transformation (to 723?K) of the deposited PAN was analyzed. It was found that at about 523?K, exothermic cyclization of polymer chains to the so-called ladder form of PAN occurred. However, the total cyclization of PAN required higher carbonization temperatures, at which gradual dehydrogenation followed by graphitization was initiated. XPS revealed that the cyclic form of PAN and a relatively large amount of carbonyl species, formed during the carbonization of the PAN/SBA-15 composite at 623?K, were responsible for the high sorption capacity in the methyl?Cethyl ketone (MEK) vapor elimination. The efficiency in the MEK adsorption was also influenced by the content of PAN-derived carbon deposited on the SBA-15 surface.     

Projection Evolution of Quantum States—the Delayed Choice Puzzle

Physics of Atomic Nuclei - We discuss the problem of the time variable in the nearly standard formulation of the quantum mechanics. In order to be able to describe the outcome of some of the...     

Capillary electrophoresis in the diagnosis of surgical site infections

A surgical site infection (SSI) is an infection that occurs after surgery in the part of the body where the surgery took place. An SSI may range from a spontaneously limited wound discharge within 7–10 days of an operation to a life‐threatening postoperative complication, such as a sternal infection after open heart surgery. Most SSIs are caused by contamination of an incision with microorganisms from the patient's own body during surgery. From the analytical point of view, the complex nature of these samples as well as the low concentrations of analytes require a system with high sensitivity and efficiency. Such situation requires a technique such as CE, which is a powerful and versatile separation technique that promises to rival HPLC when applied to the separation of both charged and neutral species. During the study, it has been demonstrated that CZE identifies characteristics of such groups of pathogens such as bacteria Gram (+) and different species of bacteria Gram (?), and also develops weekly individual profiles for patients after application of antibiotics. This was done in order to show the impact of antibiotic therapy in change “numbers” of bacteria present in the wound after surgery. The method proved to be the ideal straight specificity in the case of Escherichia coli (100%). Finally, analysis of the spectra and the second derivatives of the UV‐Vis spectra confirmed the similarity in the profiles and showed that the CZE is a great method for fast screening test in bacterial infection.     

[11]Anthrahelicene on TiO2 surfaces

Helicenes are carbon-rich materials with an ordered structure that possess interesting and remarkable electronic, chiroptical, mechanical and magnetic properties either in bulk or as single molecule devices. We report on the first attempt to anchor and organize [11]anthrahelicene ([11]AH) molecules onto a metal oxide surface. Molecular structures obtained on the (110) and (011) faces of rutile titania are characterized using scanning probe microscopy. On the (110) surface, [11]AH molecules form islands that are comprised of small domains of two types that are mirror reflections of each other and have an ordered quasi-hexagonal lattice. In contrast, molecules form unordered clusters on the (011) surface. Single molecules on both faces are imaged with sub-molecular resolution.     

Remarks on the Sibony functions and pseudometrics

We discuss some basic properties of the Sibony functions and pseudometrics.     

Determination of Volatile Halogenated Compounds in Tap and Surface Waters from the Gdańsk District

Abstract

The present method is based on preconcentration of organic contaminants on XAD-4 as sorbent, thermal desorption, mineralization and coulometric argentometric titration for the final determination of halides. The results were calculated as the total parameter VOX (volatile organic halogen) expressed as chlorine. The method has been used for the VOX determination in tap water, Vistula river water and Baltic Sea water. Sampling of the Baltic Sea water has been carried out during the research cruise of the r/v ‘Oceania’. The relatively high anthropogenic pollution of the river Vistula (c _vox = 11–45 μg Cl/cd³), Gulf of Gdańsk (c _vox = 0.6–4.5 μg Cl/dm³) and the Pomerania Bay (c _vox = 2 μg Cl/dm³) has been determined. The VOX concentration in the tap water varied between 13 and 56 μg/dm³; that is, this water is seriously polluted by volatile organic halogen compounds.