Shape memory segmented polyurethanes: dependence of behavior on nanocellulose addition and testing conditions

The response of synthesized shape memory segmented polyurethanes (PUs) was affected by the addition of cellulose nanocrystals, as well as by the various conditions selected to carry out thermomechanical cyclic tests. The PUs were synthesized from an α‐hydro‐ω‐hydroxy‐poly(ethylene oxide), tolylene‐2,4‐diisocyanate and 1,4‐butanediol as chain extender. Nanocomposites were prepared by mixing a suspension of cellulose nanocrystals in N,N‐dimethylformamide with the thermoplastic PU dissolved in the same organic solvent. The thermal properties of the neat PU and resulting composites were examined using differential scanning calorimetry. It was found that cellulose addition increases the PU soft segment melting and crystallization temperatures and the degree of crystallinity of this phase. Shape memory behavior was studied using cyclic thermal tensile tests. Both neat PU and composites exhibit shape memory properties, with fixity and recovery values that depend on heating temperature, imposed deformation, deformation rate and nanofiller addition. Copyright © 2011 Society of Chemical Industry     

Biochemical Alterations during the Obese-Aging Process in Female and Male Monosodium Glutamate (MSG)-Treated Mice

Obesity, from children to the elderly, has increased in the world at an alarming rate over the past three decades, implying long-term detrimental consequences for individual’s health. Obesity and aging are known to be risk factors for metabolic disorder development, insulin resistance and inflammation, but their relationship is not fully understood. Prevention and appropriate therapies for metabolic disorders and physical disabilities in older adults have become a major public health challenge. Hence, the aim of this study was to evaluate inflammation markers, biochemical parameters and glucose homeostasis during the obese-aging process, to understand the relationship between obesity and health span during the lifetime. In order to do this, the monosodium glutamate (MSG) obesity mice model was used, and data were evaluated at 4, 8, 12, 16 and 20 months in both female and male mice. Our results showed that obesity was a major factor contributing to premature alterations in MSG-treated mice metabolism; however, at older ages, obesity effects were attenuated and MSG-mice became more similar to normal mice. At a younger age (four months old), the Lee index, triglycerides, total cholesterol, TNF-α and transaminases levels increased; while adiponectin decreased and glucose tolerance and insulin sensitivity levels were remarkably altered. However, from 16 months old-on, the Lee index and TNF-α levels diminished significantly, while adiponectin increased, and glucose and insulin homeostasis was recovered. In summary, MSG-treated obese mice showed metabolic changes and differential susceptibility by gender throughout life and during the aging process. Understanding metabolic differences between genders during the lifespan will allow the discovery of specific preventive treatment strategies for chronic diseases and functional decline.     

Design and evaluation of a self-adhesive naproxen-loaded film prepared from a nanoparticle dispersion

Naproxen-loaded nanoparticles were used to prepare, in a one-step process, unilaminar films of Eudragit E-100 (EE-100), avoiding the use of organic solvents and assuring the homogeneity and molecular dispersion of the drug. Nanoparticle films (NP-F) and conventional films (CV-F, prepared by casting of methanolic solutions onto a Teflon disc) were assayed by their mechanical properties, skin adhesivity, and calorimetric studies to compare their behavior. Different proportions of plasticizer (triacetin) were included to evaluate the quality of the films. Film characterization included in vitro drug release studies through a cellulose membrane using Franz-type cells, and in vivo stratum corneum penetration experiments by the tape stripping technique. The results showed that NP-F were semi-transparent to transparent, suggesting a good compatibility between naproxen and EE-100. Differential calorimetric studies (DSC) confirmed a molecular dispersion of naproxen in the EE-100 matrix. Taking into account the mechanical properties of the films, a 20% triacetin concentration can be considered as optimal for both types of films. The in vitro release data obtained from both systems (NP-F and CV-F) followed the Higuchi's model for matrix systems, with the Fickian diffusion (t(0.5)) being the main release mechanism. Concerning the in vivo penetration studies, no statistical differences were found for the penetrated amount of naproxen across the stratum corneum and the depth of penetration for the two films and between the three contact times (2, 4, and 6 h). The films formulated from nanoparticle dispersions (NP-F) were shown to be effective for the transdermal administration of naproxen, and can be considered as an interesting alternative for the preparation of films with several technological advantages.     

Has the web transformed experience goods into search goods?

Klein (Journal of Business Research 41(3): 195–203, 1998) posited that the Web can transform experience goods into search goods (ES shifts). We examine her proposition in three ways. First, we critically assess the background of her proposition in light of the Web evolution in the past decade. Second, we conduct a comparison of past studies that measured the extent of search, experience, and credence (SEC) characteristics of goods. Third, we report the results of an exploratory survey on a set of commonly purchased products to benchmark possible ES shifts against the past studies. Their results indicate that SEC classification changes do not seem significant.     

Process integrated wire-bond quality control by means of cytokine-Formal Immune Networks

Ultrasonic wire bonding is one of the most frequently used techniques in semiconductor production to establish electrical interconnections. Improper bonding process parameters, wire or substrate contamination or low substrate quality are some of the causes of failed bonds. Process integrated wire-bond quality control techniques compare process feedback signals to a reference for monitoring online the quality of a bond. The feedback signals sampled at high frequencies, constitute high dimensional vectors representing the bonding process characteristics. In the area of online bond failure detection, dimensionality reduction of the input signals and feature extraction of the characteristics of the process are very demanding. Cytokine-Formal Immune Network (cFIN) is a procedure for pattern recognition which presents a low recognition failure rate and a fast recognition due to the reduction of dimensions and feature extraction of the training pattern data set produced in the learning phase. We use cytokine-Formal Immune Networks for recognizing faults present during the wire bonding process. The recognition methodology is intended to be applied into a process integrated quality control system. Further an automated optimization procedure has been developed to find optimal cFIN training parameters. Very promising results for two wire bonding process setups are shown in this paper.     

Water Disinfection Using Chitosan Microbeads With N-, C-, C-N/TiO2 By Photocatalysis Under Visible Light

Chitosan microbeads with C-doped TiO₂, N-doped TiO₂ and C,N-codoped TiO₂ were prepared to obtain photocatalysts with higher photocatalytic efficiency, active under visible light and easy to removed from aqueous medium. TiO₂ powders were synthesized by the sol–gel method and modified using glucose and ammonium nitrate as source of C and N, respectively. Scanning electron microscope (SEM), X-ray diffraction (XRD), DRUV–Vis spectra and Raman techniques, were used to characterize the modified TiO₂ powders. The structural and physicochemical properties of the microbeads were analyzed by nitrogen physisorption, functional groups were identified by Fourier transform Infrared (FT-IR) spectroscopy and microbeads were observed by optical microscopy. The microbeads photocatalytic efficiency under visible light was evaluated monitoring the E. coli growth-inhibition, determined by colony count analysis (CFU—colony forming units). Results showed effectiveness in all tested composites to inhibit E. coli growth in 24 h under visible light. Furthermore chitosan microbeads with C,N-codoped TiO₂ showed the best performance in the degradation test being the most effective composite to achieving 99.99% of E. coli growth inhibition in less than 4 h.

     

Thermal decomposition of some poly(β-hydroxyalkanoates)

The thermal decomposition of some polyhydroxyalkanoates (PHA) has been investigated by means of thermogravimetry and differential thermogravimetry. The thermal stability of the studied polyesters decreases slightly with increasing hydroxyvalerate (HV) comonomer. This result is different from those reported in the literature. Other results agree with reaction mechanisms proposed in the literature. The data from dynamic thermogravimetric experiments are consistent with a first order reaction, as would be expected from the reaction mechanism. Infrared spectra of the thermally degraded and undegraded copolymers are evidence of the cis-elimination mechanism. © 1999 Society of Chemical Industry