X-ray microscopy of novel thermoplastic/liquid crystalline polymer blends by mechanical alloying

Incorporation of liquid crystalline polymers (LCPs) into commodity polymers remains a challenge in the design of high-performance, low-cost polymeric blends. Blends of a thermoplastic polymer and a nematic LCP are produced here by mechanical alloying. Functionality sensitive X-ray microscopy reveals LCP dispersions as small as 100 nm in diameter. Intimate mixing remains upon subsequent melt processing, indicating that mechanical alloying is suited for applications such as recycling.     

Surface modification of chlorobutyl rubber by plasma polymerization

Radio frequency (r.f.) plasma polymerization of vinylidene fluoride (CH₂CF₂) has been used to modify the surface properties of chlorobutyl rubber. FTIR-ATR spectra of the treated rubbers and transmission spectra of plasma polymer films on NaCl windows indicated that as power increased the F/H ratio decreased. SIMS tests supported the FTIR results, and showed that the decrease in the F/H ratio was due to a decrease in the amount of F and an increase in the amount of H in the plasma polymer. Sliding friction measurements showed a reduction in the coefficient of friction (μ) from 3.7 for the untreated rubber to values ranging between 0.4 and 1.9 for the plasma-treated rubbers. There did not appear to be any correlation between the coefficient of friction and plasma power or monomer flow rate, and the average coefficient of friction for the plasma-treated samples was 0.9, which was lower than a commercially used silicone oil treatment (μ = 1.1–1.3). Repetitive sliding friction tests showed that the plasma- and silicone oil treated-chlorobutyl rubbers had the similar lubricating lifetimes. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1651–1660, 1997     

Quantitative EPR study on free radicals in the natural polyphenols interacting with metal ions and other environmental pollutants

Quantitative electron paramagnetic resonance (EPR) method was applied to characterise radicals stabilised in polyphenolic matrices of various biogenic materials: lichens, mosses, composts, soils, peats, brown coals and sewage sludge sediments. The investigations were carried out on raw materials and extracted fractions of humic acids (HA). General trends of g value and spin concentration changes were found. These parameters in lichens strongly depend on lichen species and air pollution. Determination of the g value and semiquinone spin concentration allows to assess degree of transformation of organic matter in compost, soil, peat and lignite. Application of gaseous ammonia as a base penetrating the organic matrices extends the possibilities and usefulness of the method. Interaction of metal ions with humic materials is illustrated by interaction of VO2+ ion with peat and lignite HA as well as demineralised (raw and carbonised) brown coal. Our investigations demonstrate that quantitative EPR is a rapid and effective monitoring method to study the influence of various environmental factors on substances containing polyphenolic matrices.     

Quiet imaging with interleaved spiral read-out

The acoustic noise generated during an MRI sequence can be effectively reduced with the help of soft gradient pulses using sinusoidal ramps. The long slope duration, however, leads to long acquisition times. The use of interleaved spiral trajectories, calculated with long gradient slopes, is proposed to reduce the acquisition time while maintaining low acoustic noise levels. The practibility of this approach is demonstrated on phantom and volunteer images.     

Image-Based Reduction of Artifacts in Multishot Echo-Planar Imaging

The method to reduce the ghost artifact in echo-planar imaging (EPI) using a phase correction derived from the image data (M. H. Buonocore and L. Gao,Magn. Reson. Med.38, 89 (1997)) is generalized to multishot (interleaved) EPI, where the artifact takes the form of multiple ghosts. The method is shown to be much more sensitive to noise when applied to standard interleaved data than is the case with single-shot EPI, because the calculation must be based on high-order ghosts of low intensity. A modified interleaving scheme is proposed for multishot EPI in which the initial trajectory direction alternates in consecutive shots and the number of shots is odd. With this scheme, only a single ghost shifted by one-half of the field of view appears just as in the single-shot EPI, and the image-based phase correction can be applied with the usual sensitivity to noise.     

On extending backwards positive definite sequences

The two-sided Hamburger moment problem¹, also called the strong one [4], has been extensively studied in recent years in connection with rational approximation. We propose to consider the question of when a sequence, say {a _n } _n=0 can be extended backwards so that the resulting sequence {a _n } _n=–N has an integral representation of the Hamburger type. This was settled (without any proof) under different circumstances in [6]. Here we wish to discuss this completely, as well as the possibility of extending {a _n } _n=0 to {a _n } _n– .     

Photometrische Bestimmung von Perchlorat mit Ferroin

Zusammenfassung Ein Verfahren zur photometrischen Bestimmung des Perchlorations wurde ausgearbeitet. Die Untersuchungslösung wird mit überschüssigem Ferroin und mit Chloroform versetzt. Der Niederschlag wird, abfiltriert und der Ferroinüberschuß im Filtrat photometrisch bestimmt. Für die Bestimmung kleiner Perchloratmengen zwischen 0,2 und 1 mg extrahiert man den gefärbten Ferroinperchloratkomplex mit n-Amylalkohol und photometriert die alkoholische Phase. Der Einfluß von Fremdionen auf die Analysenergebnisse wurde untersucht.

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Summary A method was worked out for the photometric determination of perchlorate ion. The test solution is treated with excess ferroin and chloroform. The precipitate is filtered off and the excess ferroin in the filtrate is determined photometrically. When slight amounts of perchlorate are to be determined, say between 0.2 and 1 mg, the colored ferroin-perchlorate complex is extracted withn-amyl alcohol and the alcoholic phase is photometerized. The effect of foreign ions on the analytical findings was studied.

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Résumé On a mis au point un procédé pour le dosage photométrique de l'ion perchlorate. On additionne la solution à l'étude de ferroine et de chloroforme. en excès. Le précipité est séparé par filtration et l'excès de ferroine dosé photométriquement sur le filtrat. Pour le dosage de petites quantités de perchlorate, entre 0,2 et 1 mg, on extrait le complexe coloré perchlorate de ferroine par l'alcooln-amylique et l'on effectue la photométrie sur la phase alcoolique. On a étudié l'influence des ions étrangers sur les résultats d'analyse.

     

Comparison of Flow and Transport Experiments on 3D Printed Micromodels with Direct Numerical Simulations

Understanding pore-scale flow and transport processes is important for understanding flow and transport within rocks on a larger scale. Flow experiments on small-scale micromodels can be used to experimentally investigate pore-scale flow. Current manufacturing methods of micromodels are costly and time consuming. 3D printing is an alternative method for the production of micromodels. We have been able to visualise small-scale, single-phase flow and transport processes within a 3D printed micromodel using a custom-built visualisation cell. Results have been compared with the same experiments run on a micromodel with the same geometry made from polymethyl methacrylate (PMMA, also known as Perspex). Numerical simulations of the experiments indicate that differences in experimental results between the 3D printed micromodel and the Perspex micromodel may be due to variability in print geometry and surface properties between the samples. 3D printing technology looks promising as a micromodel manufacturing method; however, further work is needed to improve the accuracy and quality of 3D printed models in terms of geometry and surface roughness.

     

XPS study of silver and copper nanoparticles demonstrated selective anticancer,proapoptotic, and antibacterial properties

Silver and copper nanoparticles were produced by an ecologically safe metal vapor synthesis (MVS) method using acetone as an organic dispersion medium. Transmission electron microscopy (TEM) showed that the specimens are spherical and polydisperse, and their average size is 2.5 nm for silver nanoparticles (Ag NPs) and 2.6 nm for copper nanoparticles (Cu NPs). X-ray photoelectron spectroscopy analyses showed that the state of silver in the nanoparticles is close to that of silver in the Ag⁰ state, whereas copper black contains two oxidized states of the metal—Cu⁺ and Cu²⁺. Biological in vitro studies demonstrated that the nanoparticles have antibacterial activity against Gram-positive and Gram-negative bacterial species. Cu NPs exhibited more prominent antibacterial effects and induced significant growth inhibition of Bacillus cereus and Escherichia coli. Both types of nanoparticles showed anticancer properties in vitro. Cu NPs induced intense cytotoxicity in cancer and normal fibroblasts in vitro cultures, but their inhibitory effect against noncancerous cells was milder compared with cancer cell lines. Ag NPs demonstrated selective cytotoxicity against human lung and cervical adenocarcinoma cell lines. Further in vitro studies indicated that the mechanism of Ag NPs and Cu NPs anticancer effects involves induction of apoptosis. The present study describes a green synthesis approach for production of biologically active silver and copper nanoparticles and highlights their potential for medical application.     

Selfadjointness of Integral and Matrix Operators

Criteria for selfadjointness of integral operators, includingmatrix operators, based on our earlier domination results areestablished. The range of applicability is elucidated by carefullychosen examples, not covered by previously known criteria.