Supramolecular inclusion complexation of polyhedral oligomeric silsesquioxane capped poly(ε‐caprolactone) with α‐cyclodextrin

Supramolecular inclusion complexes (ICs) involving polyhedral oligomeric silsesquioxane (POSS) capped poly(?‐caprolactone) (PCL) and α‐cyclodextrin (α‐CD) were investigated. POSS‐terminated PCLs with various molecular weights were prepared via the ring‐opening polymerization of ?‐caprolactone (CL) with 3‐hydroxypropylheptaphenyl POSS as an initiator. Because of the presence of the bulky silsesquioxane terminal group, the inclusion complexation between α‐CD and the POSS‐capped PCL was carried out only with a single end of a PCL chain threading inside the cavity of α‐CD, which allowed the evaluation of the effect of the POSS terminal groups on the efficiency of the inclusion complexation. The X‐ray diffraction results indicated that the organic–inorganic ICs had a channel‐type crystalline structure. The stoichiometry of the organic–inorganic ICs was quite dependent on the molecular weights of the POSS‐capped PCLs. With moderate molecular weights of the POSS‐capped PCLs (e.g., M_n =3860 or 9880), the stoichiometry was 1:1 mol/mol (CL unit/α‐CD), which was close to the literature value based on the inclusion complexation of α‐CD with normal linear PCL chains with comparable molecular weights. When the PCL chains were shorter (e.g., for the POSS‐capped PCL of M_n = 1720 or 2490), the efficiency of the inclusion complexation decreased. The decreased efficiency of the inclusion complexation could be attributed to the lower mobility of the bulky POSS group, which restricted the motion of the PCL chain attached to the silsesquioxane cage. This effect was pronounced with the decreasing length of the PCL chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1247–1259, 2007     

Dynamical systems — Past and present

Plenary lecture at the International Congress of Mathematicians (Berlin 1998, August 18–27). Reprinted from Doc. Math. J., DMV, Extra Volume ICM I, 1998, pp. 381–402. ©J.Moser, 1998.     

Most vital links and nodes in weighted networks

The n most vital links (or nodes) in a weighted network are those n links (nodes) whose removal from the network results in the greatest increase in shortest distance between two specified nodes. Preliminary results are presented for obtaining these entities.     

Alkaline phosphatase encapsulated in gellan-chitosan hybrid capsules

Alkaline phosphatase (ALP) was encapsulated in gellan-chitosan polyion complex (PIC) capsules using a convenient procedure. The recovery of ALP was about 50% when the capsules were prepared by dropping a solution of ALP and gellan mixture (ALP/gellan) into a chitosan solution. When p-nitrophenyl phosphate (p-NPP) and 5-bromo-4-chloro-3-indolyl phosphate (BCIP) were incubated with ALP/gellan-chitosan capsules as substrates for ALP, the transparent colorless capsules changed to yellow and blue, respectively. The encapsulation of ALP into the PIC capsules was also confirmed by SDS-PAGE and immunoblot analyses. The ALP and polypeptides of more than 30 kDa remained without release even after incubation at 4 degrees C for 14 d. The biochemical properties of the encapsulated ALP activity were similar to those of the intact enzyme. When the solution containing p-NPP was loaded on a column packed with ALP/gellan-chitosan capsules at 27 degrees C, approximately 75% of p-NPP was hydrolyzed by passing through the column. No significant leakage of ALP was observed during the procedure, indicating that the capsules were resistant to pressure in the chromatographic operation. Furthermore, 70% of the hydrolytic activity of the packed capsules remained after storage at 4 degrees C for one month. These results suggest that the polyion complex capsules could be useful materials for protein fixation without chemical modification. [Diagram: see text] Encapsulation of ALP into PIC capsules and the morphological changes seen in the absence of the ALP substrate and in the presence of p-NPP and BICP.     

Deposition of quasi-crystal Al-doped ZnO thin films for photovoltaic device applications

Quasi-crystal aluminum-doped zinc oxide (AZO) films were prepared by in situ radio frequency (RF) magnetron sputtering (sputtering without annealing) on glass substrates. The influence of deposition parameters on the optoelectronic and structural properties of the in situ deposited quasi-crystal AZO films was investigated in order to compare resulting samples. X-ray diffraction (XRD) patterns show that the quasi-crystal AZO thin films have excellent crystallization improved with increase of the RF power and substrate temperature, with an extremely preferential c-axis orientation exhibit sharp and narrow XRD pattern similar to that of single-crystal. Field emission scanning electron microscopy (FESEM) images show that quasi-crystal AZO thin films have uniform grains and the grain size increase with the increase of RF power and substrate temperature. Craters of irregular size with the columnar structure are observed in the quasi-crystal AZO thin films at a lower substrate temperature while many spherical shaped grains appeared at a higher substrate temperature. The average optical transmittance of all the quasi-crystal AZO films was over 85% in the 400-800 nm wavelength range. The resistivity of 4.176 × 10⁻⁴ Ω cm with the grain size of 76.4891 nm was obtained in the quasi-crystal AZO thin film deposited at 300 °C, under sputtering power of 140 W.     

A fractional order HIV-TB coinfection model with nonsingular Mittag-Leffler Law

The biological models for the study of human immunodeficiency virus (HIV) and its advanced stage acquired immune deficiency syndrome (AIDS) have been widely studied in last two decades. HIV virus can be transmitted by different means including blood, semen, preseminal fluid, rectal fluid, breast milk, and many more. Therefore, initiating HIV treatment with the TB treatment development has some advantages including less HIV-related losses and an inferior risk of HIV spread also having difficulties including incidence of immune reconstitution inflammatory syndrome (IRIS) because of a large pill encumbrance. It has been analyzed that patients with HIV have more weaker immune system and are susceptible to infections, for example, tuberculosis (TB). Keeping the importance of the HIV models, we are interested to consider an analysis of HIV-TB coinfected model in the Atangana-Baleanu fractional differential form. The model is studied for the existence, uniqueness of solution, Hyers-Ulam (HU) stability and numerical simulations with assumption of specific parameters.     

Facilitating an Elementary Engineering Design Process Module

STEM education in elementary school is guided by the understanding that engineering represents the application of science and math concepts to make life better for people. The Engineering Design Process (EDP) guides the application of creative solutions to problems. Helping teachers understand how to apply the EDP to create lessons develops a classroom where students are engaged in solving real world problems by applying the concepts they learn about science and mathematics. This article outlines a framework for developing such lessons and units, and discusses the underlying theory of systems thinking. A model lesson that uses this framework is discussed. Misconceptions regarding the EDP that children have displayed through this lesson and other design challenge lessons are highlighted. Through understanding these misconceptions, teachers can do a better job of helping students understand the system of ideas that helps engineers attack problems in the real world. Getting children ready for the 21st century requires a different outlook. Children need to tackle problems with a plan and not shrivel when at first, they fail. Seeing themselves as engineers will help more underrepresented students see engineering and other STEM fields as viable career options, which is our ultimate goal.     

On a third‐order Newton‐type method free of bilinear operators

This paper is devoted to the study of a third‐order Newton‐type method. The method is free of bilinear operators, which constitutes the main limitation of the classical third‐order iterative schemes. First, a global convergence theorem in the real case is presented. Second, a semilocal convergence theorem and some examples are analyzed, including quadratic equations and integral equations. Finally, an approximation using divided differences is proposed and used for the approximation of boundary‐value problems. Copyright © 2009 John Wiley & Sons, Ltd.     

Erfahrungen und Ergebnisse der Isotopenanwendung im Industriezweig Braunkohle

This paper presents results of a study carried out in order to assess the applicability of ³²Si for groundwater dating. Measurements of ³²Si in soil samples of the unsaturated zone, of drainage waters and plant material give a basis for estimating the ³²Si initial concentration in groundwater. Different aquifers with groundwater of young and moderate ages have been selected for groundwater studies. For obtaining independent age information tritium was found to be a suitable reference isotope. A quantitative interpretation of the ³²Si data is generally complicated by geochemical processes, preferably in the unsaturated zone. Favourable conditions concerning the use of ³²Si in hydrogeology seem to exist in phreatic sandy aquifers, in limestone aquifers, and, depending on the thickness and composition of the unsaturated zone, in sandstone aquifers. Further improvements of the ³²Si method needs a better understanding of the geochemical processes affecting this isotope.