A novel preparation method of maleic anhydride grafted syndiotactic polystyrene and its blend performance with nylon6

Summary This work is intended to provide a method for the preparation of maleic anhydride grafted syndiotactic polystyrene (sPS-g-MA). In particular, a novel solid reaction method by a radical grafting approach is investigated. The grafting reaction is performed at a solid state, where the syndiotactic polystyrene (sPS) is swollen in solvent at relatively low temperature compared to the conventional melt modification method. The formation of sPS-g-MA is directly confirmed by Fourier transform infrared spectroscopy and by the morphology observation of sPS/polyamide-6 (Nylon6) blends, when sPS-g-MA is used as a reactive compatibilizer. Received: 27 February 2002 / Revised version: 26 April 2002 / Accepted: 30 April 2002     

Improvement in "uremic" cardiomyopathy by persistent ultrafiltration

Some patients with end-stage renal disease suffer severe cardiac dilatation with functional disturbances, notably low ejection fraction (EF) and valvular regurgitation. They often have normal or low blood pressure, and tolerate ultrafiltration (UF) poorly. The aim of our study was to investigate to what extent this condition can still be improved by persistent slow UF. Twelve patients with cardiothoracic index >0.54 and EF <0.45 but otherwise uncomplicated were treated by slow, prolonged UF during hemodialysis (3 times a week) sessions, if necessary supplemented by isolated UF sessions on a separate day. Repeated chest X-rays and Doppler echocardiography were applied. During treatment periods varying from 20 to 120 days, all of the patients lost weight (12+/-10 kg) and became edema free. Cardiothoracic index decreased in all patients from a mean of 0.59+/-0.04 to 0.47+/-0.03. Blood pressure decreased when it had been elevated and increased when it was below normal. Ejection fraction increased in all of them from a mean of 0.31+/-0.9 to 0.50+/-0.9. Mitral and tricuspid regurgitation were found in every patient and disappeared or improved in all of them. Striking improvement of cardiac dilatation and dysfunction can be achieved by carefully monitored persistent UF in the majority of patients with seemingly intractable dilated cardiomyopathy.     

Novel clamping force control for electric parking brake systems

In this paper, we present a novel control method with clamping force estimation for an electric parking brake system. This simple control structure can be implemented at low cost as it does not require a clamping force sensor. The characteristic curve is conventionally used to estimate the clamping force through the angular displacement of the DC motor; however, this can result in error because of the dependence of the curve on the brake clearance between the brake pads and brake disk at release. We solve this problem by approximating the initial contact point using the angular velocity of the motor. We then propose a novel on–off control method to avoid excessive clamping forces by predicting the additional angular displacement after power-off caused by the inertia effect. Finally, we experimentally validate our proposed control method.     

Enthalpy vs Entropy Driven Complexation of Homoallylic Alcohols by Rh(I) Complexes

The thermodynamics of binding between several homoallylic alcohols and simple olefinic Rh(I) compounds was examined with (1)H NMR spectroscopy and ITC. (1)H NMR titrations revealed moderate binding of these alcohols with [Rh(COD)(2)](+) (1) and [Rh(COD)(CH(3)CN)(2)](+) (3), but weaker binding with [Rh(NBD)(2)](+) (2). ITC indicated that the complexation with [Rh(COD)(2)](+) is mainly governed by enthalpy whereas binding with [Rh(COD)(CH(3)CN)(2)](+) is entirely driven by entropy. The thermodynamic parameters for the homoallylic alcohol binding of Rh(I) complexes 1-3 are consistent with crystallographic data.     

Dynamic multi-swarm particle swarm optimizer with harmony search

In this paper, the dynamic multi-swarm particle swarm optimizer (DMS-PSO) is improved by hybridizing it with the harmony search (HS) algorithm and the resulting algorithm is abbreviated as DMS-PSO-HS. We present a novel approach to merge the HS algorithm into each sub-swarm of the DMS-PSO. Combining the exploration capabilities of the DMS-PSO and the stochastic exploitation of the HS, the DMS-PSO-HS is developed. The whole DMS-PSO population is divided into a large number of small and dynamic sub-swarms which are also individual HS populations. These sub-swarms are regrouped frequently and information is exchanged among the particles in the whole swarm. The DMS-PSO-HS demonstrates improved on multimodal and composition test problems when compared with the DMS-PSO and the HS.     

Effects of Mg doping concentration on the band gap of ZnO/Mg x Zn1−x O multilayer thin films prepared using pulsed laser deposition method

Epitaxial ZnO/Mg _x Zn_1-x O multilayer thin films (x?=?0~0.15) were prepared on c-Al₂O₃ substrates by pulsed laser deposition and their crystallinity and optical properties were investigated using X-ray diffraction, TEM, and UV-Vis spectroscopy. ZnO/Mg _x Zn_1-x O multilayer thin films were grown by stacking alternate layers of ZnO and Mg _x Zn_1?x O with laser fluence of 3 J/cm², repetition rate of 5 Hz, substrate temperature of 600 °C, and oxygen partial pressure of 5?×?10^–4 Torr. The thickness of individual ZnO and Mg _x Zn_1?x O layers was maintained at 3 and 6 nm, respectively, and the total thickness of the films was kept in 300 nm. X-ray diffraction results showed that the multilayer thin films were grown epitaxially on c-Al₂O₃ substrates with an epitaxial orientation relationship of $\left. {\left( {0001} \right)\left[ {10\bar 11} \right]_{{\text{multilayer}}} } \right\|\left( {0001} \right)\left[ {10\bar 11} \right]_{{\text{Al}}_{\text{2}} {\text{O}}_{\text{3}} } $ . Cross-sectional TEM micrographs showed alternating layers of bright and dark contrast, indicating the formation of ZnO/Mg _x Zn_1?x O multilayer thin films. The 2θ value of Mg _x Zn_1?x O (0002) peak increased from 34.30° at x?=?0 to 34.67° at x?=?0.15 with increasing Mg doping concentration in the multilayer thin films. The absorption edge in the UV-Vis spectra shifted to shorter wavelength from 360 at x?=?0 to 342 nm at x?=?0.15 and the band gap energy increased from 3.27 eV at x?=?0 to 3.54 eV at x?=?0.15.     

Rheological properties and stability of magnetorheological fluids using viscoelastic medium and nanoadditives

In order to improve the stability of magnetorheological (MR) fluids, viscoelastic medium having 2.2 Pa yield stress has been used as a continuous phase and nanosized CrO₂ particles are added too. The rheological properties as well as the dispersion stability of MR fluids have been studied by using a stress-controlled rheometer and sedimentation test. The steady-shear MR response was independent of the continuous and nano additives and the fieldinduced yield stress increased subquadratically with the flux density. Since the constant stress is generated within the limit of zero shear rate, the plateau in the flow curve corresponds to the Bingham yield stress. Under an external field, the yield stress varied as B^3/2. The yield stress has an approximately linear relation with the particle volume fraction.     

Optical properties and characteristics of the cdse nanoparticles synthesized at room temperature

CdSe nanoparticles were synthesized by using colloidal methods at room temperature. Nanoparticle size was controlled by the amount of stabilizer, pH, and stabilizer type and was characterized by TEM and XRD. All the synthesized CdSe nanoparticles showed the quantum confinement effect. With increased amounts of mercaptoacetic acid as a stabilizer, the size of nanoparticles decreased. The UV-VIS absorption and photoluminescence (PL) properties could also be tailored by controlling particle size. The solubility in organic solvent and the PL characteristics were enhanced through surface capping by an organic passivator.     

CLA formation in oils during hydrogenation process as affected by catalyst types,catalyst contents,hydrogen pressure,and oil species

The effects of types and amount of catalysts, hydrogen pressure, and kinds of vegetable oils on the formation of CLA isomers were studied during hydrogenation. CLA isomers were identified by using a silver ion-impregnated high-performance liquid chromatograph and 100-m cyano-capillary column gas chromatograph. A selective catalyst (SP-7) produced a considerably higher content of CLA in soybean oil than nonselective catalysts. The maximal quantity of CLA produced in soybean oil during hydrogenation increased greatly with increasing amount of catalyst. By increasing the amount of selective catalyst from 0.05 to 0.3%, the quantity of total CLA obtained was about 1.9 times higher. Changes in hydrogen pressure also greatly influenced total CLA formed. By decreasing hydrogen pressure from 0.24 to 0.024 MPa, the quantity of CLA obtained was about 1.3 times higher. With different oil species (soybean, cottonseed, and corn oils), the time to reach the maximal quantity of CLA was different under the same hydrogenation conditions. However, the maximal quantity of CLA and proportion of CLA isomers formed were almost identical, regardless of oil species tested, under the same hydrogenation conditions.