Switching Stability of Automotive Roll Dynamics Subject to Interval Uncertainty

In this paper we apply some recent results on the stability of switched systems with interval uncertainty for analyzing the roll stability of automotive vehicles subject to bounded parametric uncertainties and switching. The application is motivated by the fact that the roll dynamics of an automotive vehicle is affected in a significant and a nonlinear fashion due to possible sudden switches in the vehicle's center of gravity (CG) height, as well as the uncertainty in the suspension parameters. Utilizing a recent stability result, it is possible to model such parametric variations as bounded interval uncertainties for this problem, and obtain easily verifiable conditions for analyzing the stability of the resulting switched/uncertain system. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

New approaches to characterize polymeric oil additives in solution based on pyrene excimer fluorescence

Maleated polyolefins (MaPOs) such as maleated ethylene propylene copolymers or polyisobutylene terminated at one end with a succininic anhydride can be used as polymeric dispersants in engine oils after reaction with polyamines while unmodified EP copolymers improve the viscosity index of oils. MaPOs can also be labeled with pyrene derivatives to generate pyrene‐labeled polyolefins (PyLPOs) as fluorescent mimics of oil additives and pyrene excimer fluorescence (PEF) can be applied to probe their behavior in solution. This review describes new methodology that was recently implemented to characterize the complex fluorescence signal emitted by PyLPOs by using steady‐state and time‐resolved fluorescence. This methodology enables one to gain quantitative information about the level of clustering of the succinic pendants along a maleated polyolefins and intra‐ and intermolecular aggregation of polyolefins in solution. Such information is relevant to scientists aiming to characterize polymeric oil additives used in engine oil. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 7–18     

Ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst

The ring‐opening metathesis polymerization of cyclododecene using an electrochemically reduced tungsten‐based catalyst (WCl₆? e^?? Al? CH₂Cl₂) is described. In addition, the influence of reaction conditions on the polymerization yield was determined. The resulting polymer has been characterized by NMR, IR, gel permeation chromatography and differential scanning calorimetry. The glass transition temperature and melting point of the polydodecenamer are 19.6°C and 70.0°C respectively. Furthermore, cyclododecene has been polymerized into a low‐molecular‐weight polymer (12.0 × 10³) with a polydispersity of 2.06 in high yields (94%). IR and NMR analysis indicate that the polydodecenamer has a high trans content (60%). Copyright © 2004 John Wiley & Sons, Ltd.     

Nanoscale elastic modulus variation in loaded polymeric micelle reactors

Tapping mode atomic force microscopy (TM-AFM) enables mapping of chemical composition at the nanoscale by taking advantage of the variation in phase angle shift arising from an embedded second phase. We demonstrate that phase contrast can be attributed to the variation in elastic modulus during the imaging of zinc acetate (ZnAc)-loaded reverse polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock co-polymer micelles less than 100 nm in diameter. Three sample configurations were characterized: (i) a 31.6 μm thick polystyrene (PS) support film for eliminating the substrate contribution, (ii) an unfilled PS-b-P2VP micelle supported by the same PS film, and (iii) a ZnAc-loaded PS-b-P2VP micelle supported by the same PS film. Force-indentation (F-I) curves were measured over unloaded micelles on the PS film and over loaded micelles on the PS film, using standard tapping mode probes of three different spring constants, the same cantilevers used for imaging of the samples before and after loading. For calibration of the tip geometry, nanoindentation was performed on the bare PS film. The resulting elastic modulus values extracted by applying the Hertz model were 8.26 ± 3.43 GPa over the loaded micelles and 4.17 ± 1.65 GPa over the unloaded micelles, confirming that phase contrast images of a monolayer of loaded micelles represent maps of the nanoscale chemical and mechanical variation. By calibrating the tip geometry indirectly using a known soft material, we are able to use the same standard tapping mode cantilevers for both imaging and indentation.     

Preconcentration of beryllium via octadecyl silica gel microparticles doped with aluminon, and its determination by flame atomic absorption spectrometry

A simple and sensitive method is presented for solid phase extraction (SPE) and preconcentration of trace quantities of beryllium using octadecyl silica gel modifed with aurin tricarboxylic acid (aluminon). Beryllium is then determined by flame atomic absorption spectroscopy. Parameters affecting SPE such as pH, sample solution and eluent flow rate, type, concentration and volume of eluent, interfering ions and breakthrough volume, were investigated. Under optimal conditions, the beryllium ions were retained on the sorbent at pH 6–6.7, while 3.0 mL of 0.05 mol L^?1 HNO₃ is sufficient to elute the ions. The limit of detection (LOD) based on 3σ was 0.8 µg L^?1 for 250 mL sample solution and 5 mL 0.05 mol L^?1 HNO₃ as eluent. The LOD can reach 0.1 µg L^?1 for 1 L sample solution and 3 mL of 0.05 mol L^?1 HNO₃. The accuracy and precision (RSD %) of the method is >90% and <10%, respectively. The method was applied to the determination of beryllium in aqueous samples.     

Improved molecular weight control in ring‐opening metathesis polymerization reactions in organic and aqueous media using N‐heterocyclic carbene–ruthenium arene/alkyne catalyst systems

A binary catalytic system, RuCl₂(N‐heterocyclic carbene)(p‐cymene)/alkyne, was developed for improved molecular weight control in ring‐opening metathesis polymerization (ROMP) reactions of norbornene derivatives in organic and aqueous media. Monometallic ruthenium arene compounds were activated using aryl and aliphatic terminal alkynes to form highly active metathesis species. The effects of alkyne structure and concentration on the overall catalytic activity were systematically investigated. The catalytic activity of the metathesis active species can be tuned by varying alkyne substituents. Also, the initiation rate of the ROMP reaction can be tuned by increasing the alkyne‐to‐Ru ratio. ROMP polymers with a wide range of molecular weights (91–832 kDa) were isolated in organic media, whereas polymers with a molecular weight range of 110–280 kDa with average particle sizes of 150–250 nm were isolated in aqueous media. Copyright © 2016 John Wiley & Sons, Ltd.     

Acceleration of osteogenic differentiation by sustained release of BMP2 in PLLA/graphene oxide nanofibrous scaffold

After about three decades of experience, tissue engineering has become one of the most important approaches in reconstructive medical research to treat non‐self‐healing bone injuries and lesions. Herein, nanofibrous composite scaffolds fabricated by electrospinning, which containing of poly(L‐lactic acid) (PLLA), graphene oxide (GO), and bone morphogenetic protein 2 (BMP2) for bone tissue engineering applications. After structural evaluations, adipose tissue derived mesenchymal stem cells (AT‐MSCs) were applied to monitor scaffold's biological behavior and osteoinductivity properties. All fabricated scaffolds had nanofibrous structure with interconnected pores, bead free, and well mechanical properties. But the best biological behavior including cell attachment, protein adsorption, and support cells proliferation was detected by PLLA‐GO‐BMP2 nanofibrous scaffold compared to the PLLA and PLLA‐GO. Moreover, detected ALP activity, calcium content and expression level of bone‐related gene markers in AT‐MSCs grown on PLLA‐GO‐BMP2 nanofibrous scaffold was also significantly promoted in compression with the cells grown on other scaffolds. In fact, the simultaneous presence of two factors, GO and BMP2, in the PLLA nanofibrous scaffold structure has a synergistic effect and therefore has a promising potential for tissue engineering applications in the repair of bone lesions.     

Decentralised Control Design of Lateral and Vertical Vehicle Dynamics using Passivity

In this paper, we present a novel methodology to design block–diagonal stable decentralised controllers based on the Kalman–Yakubovich–Popov lemma. The approach yields closed–loop systems that are robust with respect to parameter uncertainty and structural perturbations. We demonstrate the methodology by designing controllers for the lateral and vertical subsystems of a vehicle emulator; namely, a test vehicle that can mimic the behaviour of a wide range of vehicles. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)