Polyaniline‐modified cellulose nanofibrils as reinforcement of a smart polyurethane

Segmented polyurethanes exhibiting shape memory properties were modified by the addition of polyaniline (PANI)‐coated cellulose nanofibrils (CNFs). The two‐phase structure of the polymer is responsible for the material's ability to ‘remember’ and autonomously recover its original shape after being deformed in response to an external thermal stimulus. PANI was grown on the surface of the CNFs via in situ polymerization. Modified nanocrystals were added to the segmented polyurethane in concentrations ranging from 0 to 15 wt%. The changes in the material properties associated with the percolation of the coated fibrils appear at higher concentrations than previously observed for non‐modified CNFs, which suggests that fibril agglomeration is occurring due to the PANI coating. The shape memory behavior of the composites is maintained at about the same level as that of the unfilled polyurethane only up to 4 wt% of fibrils. At higher concentrations, the rigidity of the nanofibrils as well as their interaction with the hard‐segment phase and the increasing difficulty of dispersing them in the polymer collaborate to produce early breakage of the specimens when stretched at temperatures above the melting point of the soft segments. Copyright © 2010 Society of Chemical Industry     

Monoolein–Water Liquid Crystalline Gels of Gentamicin as Bioresorbable Implants for the Local Treatment of Chronic Osteomyelitis: In Vitro Characterization

To maximize the efficacy of chronic osteomyelitis antibiotherapy while reducing antibiotic systemic toxicity, as well as time and costs of hospitalizations, it has been thought that monoolein–water gels incorporating gentamicin sulfate could be used as local, bioresorbable, and sustained-release implants. For this purpose, four formulations were examined with regard to their physicochemical and in vitro drug release characteristics. Hot stage microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction showed cubic liquid crystalline and eutectic structures. The more suitable formulation consisting of 80–15–5% wt/wt monoolein–water–gentamicin sulfate progressively released the antibiotic for a period of 3 weeks without burst effect. Moreover, the content and the release profile of gentamicin sulfate were not significantly changed after storage at 2–6°C for a period of 10 months.     

Can Brazil replace 5% of the 2025 gasoline world demand with ethanol?

Increasing use of petroleum, coupled with concern for global warming, demands the development and institution of CO₂ reducing, non-fossil fuel-based alternative energy-generating strategies. Ethanol is a potential alternative, particularly when produced in a sustainable way as is envisioned for sugarcane in Brazil. We consider the expansion of sugarcane-derived ethanol to displace 5% of projected gasoline use worldwide in 2025. With existing technology, 21 million hectares of land will be required to produce the necessary ethanol. This is less than 7% of current Brazilian agricultural land and equivalent to current soybean land use. New production lands come from pasture made available through improving pasture management in the cattle industry. With the continued introduction of new cane varieties (annual yield increases of about 1.6%) and new ethanol production technologies, namely the hydrolysis of bagasse to sugars for ethanol production and sugarcane trash collection providing renewable process energy production, this could reduce these modest land requirements by 29–38%.     

Nonlinearizable single-input control systems do not admit stationary symmetries

The main result of the paper states that almost any analytic single-input control system, which is truly nonlinear, that is not feedback linearizable, with controllable linearization at an equilibrium point, does not admit any symmetry preserving that point. By almost any system, we mean that we exclude a small class of odd systems, that admit just one nontrivial symmetry conjugated to minus identity. The obtained results are based on a recent classification of nonlinear single-input systems under formal feedback. We also describe symmetries of feedback linearizable systems.     

Illumination of light vectors modulated in 3-D photoelastic media

Summary The dependency of the illumination of a light vector that is subjected to modulation along its path in a three-dimensional photoelastic medium, on the rotation of the principal directions (RPD) of stresses is investigated. The consistency and characteristics of the interaction of the light intensity and the RPD for three different photoelastic materials are explored. The deviation of the rotation of the optical axes from those of the principal ones, in 3-D birefringent material, is illustrated. Furthermore, the interrelation of this deviation and the magnitude of the RPD is studied. The experimentally obtained results are shown in four diagrams.With 7 Figures     

High numerical aperture in multimode microstructured optical fibers

Microstructured or "air-clad" fibers, with air holes surrounding a large core, have recently demonstrated much wider light-acceptance angles than conventional fibers. An original and accurate method is presented for determining the numerical aperture of such fibers using leaky modes. The dependence on length, wavelength, and various microstructure dimensions are evaluated for the first time for a class of fibers that exhibit exceptionally high numerical apertures. These results show excellent agreement with published measurements on similar fibers and verify that bridge thicknesses much smaller than the wavelength are required for high numerical apertures.     

Specific interactions study in complexes of poly(mono-n-alkyl itaconates) with tertiary polyamides

This paper reports an FT-IR study of blends of poly(mono-n-alkyl itaconates) with poly(N,N-dimethylacrylamide) (PDMA) and poly(ethyloxazoline) (PEOX). Strong hydrogen bonding has been found, and both polybases have shown similar acceptor strengths. Derivative techniques show asymmetric profiles for the free carbonyl band of the polybases, resulting in shifted band locations. The extent of the interassociation has been estimated by spectral curve fitting of the polybase carbonyl band. The results show that the interaction degree in blends with PEOX does not depend on the length of the poly(monoalkyl itaconate) side group, while an inter-associating ability loss is observed in blends with PDMA as the side-group size of the polyacid increases. This different behavior is attributed to the greater interspacing between vicinal carbonyl groups in PEOX. This band shows conformational sensitivity and reflects the conformational changes that occur as the steric hindrances present in the medium (due to the bulky side groups of the polyacids) increase.     

Strict feedforward control systems,linearisability, and convergent normal forms

This article discusses the feedback equivalence of multi-inputs feedforward control systems via smooth (resp. analytic) feedback transformations. We first address the state (resp. feedback) linearisation problem, and provide easily computable algorithms that yield explicit state (resp. feedback) linearising coordinates for systems in strict feedforward form. The application of the algorithms does not require checking the commutativity (resp. involutivity) of the distributions associated with the system, and the algorithms fail after few steps if the system is not linearisable. In the latter case, the algorithms are extended to provide coordinate systems bringing the system into a normal form which is a smooth (resp. analytic) counterpart of Kang's formal normal form. Illustrative examples for both the linearisation and convergent normal form include the vertical take off and landing aircraft, the multi-vehicle wireless testbed among others.     

Impact of Multimedia-Based Instruction on Learning and Retention

Studies measuring and evaluating the impact of the same multimedia-based education on learners in universities and high schools are a relatively new phenomenon. This study provides a summary of the results from research on the effects of multimedia-based safety education conducted by the M. E. Rinker Sr. School of Building Construction at the University of Florida. The findings are presented along with their related statistical test results. The findings indicate multimedia-based, self-paced learning offers very distinct advantages over traditional, instructor-led classroom learning. Overall, both the high-school and university student groups involved in the study exhibited superior retention rates when learning from the multimedia-based materials. Higher scoring students in the classroom showed little difference in either media, while students who tended to score at the low end of the grading scale uniformly scored higher on multimedia-based materials. The reduced variation in student performance based on test scores in the CD-ROM instruction indicates the positive effects of multimedia-based instruction.