Effects of ultrasonic oscillations on rheological behavior and mechanical properties of novel propylene‐based plastomers

The effects of ultrasonic oscillations on the die pressure, productivity of extrusion, melt apparent viscosity, melt surface appearance, and die swell of novel propylene‐based plastomers were studied in a specially designed ultrasonic oscillations extrusion system developed in our laboratory. The effects of ultrasonic oscillations on molecular weights, tensile strength, and dynamic mechanical properties of extrudates were also studied. The experimental results showed that the presence of ultrasonic oscillations during extrusion could significantly increase the productivity of plastomers at the same die pressure, and reduce die swell and melt fracture such as sharkskin at a given screw rotation speed. The die pressure and apparent viscosity of plastomers remarkably decreased with increasing ultrasonic intensity. Introduction of ultrasonic oscillations into plastomer melts can improve their processibility. The possible mechanism for ultrasonic improvement of rheological behavior was also proposed in this article. Under certain conditions, ultrasound‐assisted extrusion could slightly decrease the glass transition temperature (T_g) and storage modulus of plastomers due to the minor reduction in molecular weights, but showed no significant impact on yield strength and strength at break. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Use-dependent effects of the class III antiarrhythmic agent NE-10064 (azimilide) on cardiac repolarization: block of delayed rectifier potassium and L-type calcium currents

We studied the effects of NE-10064 (azimilide), a new antiarrhythmic agent reported to be a selective blocker of the slowly activating component of the delayed rectifier, IKs. In ferret papillary muscles, NE-10064 increased effective refractory period (ERP) and decreased isometric twitch tension in a concentration-dependent manner (0.3-30 microM). Increases in ERP showed reverse use-dependence, and were greater at 1 than at 3 Hz. In contrast, changes in tension were use dependent, with larger decreases observed at 3 than at 1 Hz. In guinea pig ventricular myocytes, NE-10064 (0.3-3 microM) significantly prolonged action potential duration (APD) at 1 Hz. At 3 Hz, NE-10064 (0.3-1 microM) increased APD only slightly, and at 10 microM decreased APD and the plateau potential. NE-10064 potently blocked the rapidly activating component of the delayed rectifier, IKr (IC50 0.4 microM), and inhibited IKs (IC50 3 microM) with nearly 10-fold less potency. NE-10064 (10 microM) did not block the inward rectifier potassium current (IKl). NE-10064 (10 microM) blocked the L-type calcium current (ICa) in a use-dependent manner; block was greater at 3 than at 1 Hz. We conclude that (a) NE-10064's block of potassium currents is relatively selective for IKr over IKs, (b) NE-10064 inhibits ICa in a use-dependent fashion, and (c) NE-10064's effects on ERP and tension in papillary muscle as well as APD and action potential plateau level in myocytes may be explained by its potassium and calcium channel blocking properties.     

The role of elastic property mismatch in the failure of ceramic composites

Numerical analysis was undertaken to simulate a modification of the normalized stress-intensity factor applicable when the crack tip is in the vicinity of an interface separating materials of differing elastic properties. It is predicted that when the initial crack is subcritically extended to the interface, the strength of the sample is greater than if the failure occurred from the initial crack, without arrest at the interface. The fracture behaviour of microcracking on a polished WC/Si₃N₄ sample was examined. Crack branching, deviation and arrest were observed to depend on the instantly released energy.     

Low temperature performance of graphite electrode in Li-ion cells

We studied low temperature performance of Li/graphite cell. Results show that capacity of the graphite electrode falls significantly in the temperature range of 0 to −20 °C. When lithiation and delithiation are both carried out at −20 °C, graphite only retains 12% of the room temperature capacity. However, delithiation capacity of graphite increases to 92% of the room temperature value if the lithiation is carried out at room temperature. We believe that the poor low temperature performance of the cell is due to slow kinetics of lithium ion diffusion in graphite rather than low ionic conductivity of electrolyte and solid electrolyte interface (SEI) on the graphite surface. During lithiation and delithiation processes, lithium ion has the similar apparent chemical diffusion coefficient of 10⁻⁹-10⁻¹⁰ cm²/s at 20 °C, depending on the state of lithiation of graphite. We observed a dramatic decrease in lithium ion diffusivity in the temperature range of 0 to −20 °C, and that at low temperatures of <−20 °C, lithium ion has higher diffusivity in the delithiated graphite than in the lithiated one. We also observed that temperature dependence of cycling behavior of the Li/graphite cell follows the change of lithium ion diffusivity.     

Transesterification-controlled compatibility and microfibrillation in PC-ABS composites reinforced by phosphorus-containing thermotropic liquid crystalline polyester

For polymer/liquid crystal polymer (LCP) blend systems, the in-situ fibrillation of LCP in polymer matrix can result in the self-reinforcement of polymer/LCP composites. How to control the microfibrillation of LCP in matrix is a key to enhance the mechanical properties of composites. In this paper, we investigated the transesterification-controlled compatibility and microfibrillation of phosphorus-containing thermotropic liquid crystalline polyester, poly(p-hydroxybenzoate-co-DOPO-hydroquinone ethylene terephthalate) (PHBDET) in the PC/acrylonitrile-butadiene-styrene copolymer blend (PC-ABS) during the melt processing. A standard mode and temperature-modulated differential scanning calorimetry (DSC and TMDSC) and ¹³C nuclear magnetic resonance (¹³C NMR) were used to investigate the transesterification and compatibility of PHBDET with PC-ABS. Microstructures, rheological and mechanical properties of the composites were also studied via scanning electron microscopy (SEM), dynamic rheological measurement and universal material testing machine. The results showed that the extent of transesterification could influence the compatibility of PHBDET with PC-ABS, and could be controlled by processing temperature and time. The improved compatibility was not always favorable for the microfibrillation of PHBDET in PC-ABS, but a certain extent of transesterification showed a positive influence on the tensile properties of the composites. Therefore, there existed an optimal extent of transesterification, in which the composite could show a good balance of compatibility and tensile properties.     

Fabrication of porous nickel oxide film with open macropores by electrophoresis and electrodeposition for electrochemical capacitors

The electrophoretic deposition of polystyrene sphere monolayer as a template for anodic electrodeposition of interconnected nickel oxide nanoflakes is explored. Result indicates that a nickel oxide film with nanoflakes and open macropores has superior capacitive behavior. A nickel oxide film with interconnected nanoflakes is of great importance for electrochemical capacitors due to the high-specific surface area, fast redox reactions, and shortened diffusion path in solid phase. The open macropores may facilitate the electrolyte penetration and ion migration, therefore increasing the utilization of nickel oxide due to the increased surface area for electrochemical reactions. The specific capacitance of a nickel oxide film with open macropores at a scan rate of 10 mV s⁻¹ reaches as high as 351 F g⁻¹, which is 2.5 times higher than that of the bare nickel oxide film (140 F g⁻¹).     

Biokinetics and dosimetry of titanium tritide particles in the lung

BACKGROUND: Ciprofloxacin (CFLX) is a fluoroquinolone antibiotic with a broad antimicrobial spectrum. This study was performed to examine the retinal toxicity of free and liposome-incorporated CFLX in rabbit eyes after intravitreal injection. MATERIALS AND METHODS: Free CFLX in doses of 100, 250, 500, 1,000 and 2,000 microg was injected into the midvitreous of rabbit eyes (n = 28). To prolong the intravitreal antibacterial level, CFLX was incorporated into multilamellar liposomes: 0.1 ml of this suspension ( wedge 273.6 microg CFLX) was injected into the midvitreous of a second group of rabbit eyes (n = 6). The other eye served as a control and received normal saline solution or empty liposomes, respectively. Before injection and at the end of follow-up an electroretinogram (ERG) was obtained. After a follow-up of 1, 14 and 28 days the animals were perfused with glutaraldehyde and the eyes were examined by light and transmission electron microscopy. RESULTS: Significant reduction of the ERG was observed after 2,000 microg free CFLX in 4 out of 6 eyes after 14 days. Fourteen days after injection of 2,000 microg CFLX the central retina showed pigmentary changes in 4 out of 6 eyes. In the second group the ERG as well as the histologic studies did not reveal any pathologic changes after injection of liposome-incorporated CFLX compared to the control eyes. CONCLUSION: In therapeutic doses of 100-500 microg, free CFLX does not have retinal toxicity in rabbit eyes. No retinal toxicity was observed after intravitreal injection of liposome-incorporated CFLX.     

Study of the charging process of a LiCoO2-based Li-ion battery

A three-electrode Li-ion cell with metallic lithium as the reference electrode was designed to study the charging process of Li-ion cells. The cell was connected to three independent testing channels, of which two channels shared the same lithium reference to measure the potentials of anode and cathode, respectively. A graphite/LiCoO₂ cell with a C/A ratio, i.e., the reversible capacity ratio of the cathode to anode, of 0.985 was assembled and cycled using a normal constant-current/constant-voltage (CC/CV) charging procedure, during which the potentials of the anode and cathode were recorded. The results showed that lithium plating occurred under most of the charging conditions, especially at high currents and at low temperatures. Even in the region of CC charging, the potential of the graphite might drop below 0 V versus Li⁺/Li. As a result, lithium plating and re-intercalating of the plated lithium into the graphite coexist, which resulted in a low charging capacity. When the current exceeded a certain level (0.4C in the present case), increasing the current could not shorten the charging time significantly, instead it aggravated lithium plating and prolonged the CV charging time. In addition, we found that lowering the battery temperature significantly aggravated lithium plating. At −20 °C, for example, the CC charging became impossible and lithium plating accompanied the entire charging process. For an improved charging performance, an optimized C/A ratio of 0.85–0.90 is proposed for the graphite/LiCoO₂ Li-ion cell. A high C/A ratio results in lithium plating onto the anode, while a low ratio results in overcharge of the cathode.     

Process-controlled staggered ambipolar amorphous-silicon thin-filmtransistor

The results of measurements performed on amorphous-silicon thin-film transistors (TFTs) are presented and interpreted. Both unipolar and ambipolar effect TFTs are obtained in the experiments. Whether they possess unipolar or ambipolar characteristics is controlled by the interface properties between gate insulator and amorphous silicon. With the different compositions of hybrid gate insulators, the devices show different I-V characteristics. A simple method for estimating film parameters of amorphous silicon and device parameters of the TFTs is developed. The characteristic energy of an amorphous-silicon film is obtained from the slope of the ratio of saturation current to transconductance. Threshold voltages and flatband voltages of the TFTs can also be obtained using this method     

ANODIC REACTIONS OF PROPYLENE IN THE BROMIDE AQUEOUS SOLUTIONS

The formation of propylene oxide actually occurred in the homogeneous bromide aqueous solutions for the anodic oxidation of propylene. It was found that the selectivity was very high and the current yield was mainly affected by the pH values and the spaces between the electrodes. The effect of pH values on the distributions of different types of ions in the solution was also described.