Growth of FePt nanocrystals by a single bimetallic precursor [(CO)3Fe(mu-dppm)(mu-CO)PtCl2

A new single source approach was developed to synthesize face-centered tetragonal (fct) FePt nanoparticles using bimetallic compound (CO)3Fe(mu-dppm)(mu-CO)PtCl2, which has been characterized by single crystal X-ray diffraction and was used as the precursor to ensure the accurate stoichiometry of the final FePt product; the ability of the molecular complex to act as a single source precursor for the formation of fct FePt nanocrystals with an average diameter of 3.2 nm has been demonstrated.     

Orientation of crystallites in lightly crosslinked isotactic polypropylene crystallized from the melt under uniaxial compression

A lightly crosslinked polymer film was made from isotactic polypropylene by gammaray irradiation in an acetylene atmosphere. When the crosslinked polymer film was crystallized from the melt under uniaxial compression, a unique alignment of crystallites is found. The (040) crystal plane is preferentially oriented parallel to the film surface at relatively low degrees of compression, and the (110) and (130) crystal planes are oriented parallel to the film surface at higher degrees of compression. The origin of these orientations, analogous to that previously found in a lightly crosslinked polyethylene, is discussed.     

Design of polyvinyl alcohol hydrogel as a controlled-release vehicle for rectal administration of dl-propranolol-HCl and atenolol

Preparations of beta-blockers, propranolol-HCl and atenolol, in poly(vinyl alcohol) (PVA) hydrogel were designed for the therapeutic treatment of hypertension by transrectal delivery. In vitro release characteristics and plasma drug concentration profiles after rectal administration in rats and dogs were examined. The PVA hydrogels containing beta-blockers were prepared by a low-temperature crystallization method. The release of beta-blockers from hydrogel preparations was consistent with Fickian diffusion (Higuchi model); the drug release versus the square root of release time profile gave a straight line over 60% of the total release process. The release of beta-blockers from hydrogel preparations increased at higher concentrations of PVA in the hydrogel preparations and was not affected by the pH of hydrogel preparations. Plasma concentrations of beta-blockers after rectal administration of hydrogels were higher than those after administration of suppositories (Witepsol H-15) in rats and dogs. The drug plasma concentrations increased at higher concentrations of PVA in hydrogel preparations. In the case of propranolol, which is a hepatic high-clearance drug, area under the blood concentration curve, 0-8 h after rectal administration of a hydrogel preparation (20% w/w PVA, pH 7.0) was 2.16 times and 5.26 times higher than those obtained with Witepsol H-15 suppository and oral administration, respectively. Rectal administration with PVA hydrogels is a favorable route for a hepatic high-clearance drug such as propranolol.     

Development of a vision-based lane detection system considering configuration aspects

Vision-based lane-sensing systems require accurate and robust sensing performance in lane detection. Besides, there exists trade-off between the computational burden and processor cost, which should be considered for implementing the systems in passenger cars. In this paper, a stereo vision-based lane detection system considering sensor configuration aspects such as field of view (FOV), span pixels, resolution, etc is developed. An inverse perspective mapping method is formulated based on the relative correspondence between the left and right cameras so that the 3D road geometry can be reconstructed in a robust manner. The selection rule of the sensor configuration and specifications is investigated for a standard highway. Based on the selected sensor configurations, it is shown that sensing region range on the camera image coordinate can be determined for the best lane-sensing performance. The proposed system is implemented on a passenger car and its real-time sensing performance is verified experimentally.     

Synthesis and Evaluation of Graphene Aerogel-Supported MnxFe3−xO4 for Oxygen Reduction in Urea/O2 Fuel Cells

Graphene aerogel-supported manganese ferrite (Mn_xFe_3−xO₄/GAs) and reduced-graphene oxide/manganese ferrite composite (MnFe₂O₄/rGO) were synthesized and studied as cathode catalysts for oxygen reduction reactions in urea/O₂ fuel cells. MnFe₂O₄/GAs exhibited a 3D framework with a continuous macroporous structure. Among the investigated Fe/Mn ratios, the more positive oxygen reduction onset potential was observed with Fe/Mn=2/1. The half-wave potential of MnFe₂O₄/GAs was considerably more positive than that of MnFe₂O₄/rGO and comparable with that of Pt/C, while the stability of MnFe₂O₄/GAs significantly higher than that of Pt/C. The best urea/O₂ fuel cell performance was also observed with the MnFe₂O₄/GAs. The MnFe₂O₄/GAs exhibited an OCV of 0.713 V and a maximum power density of 1.7 mW cm⁻² at 60 °C. Thus, this work shows that 3D structured graphene aerogel-supported MnFe₂O₄ catalysts can be used as an efficient cathode material for alkaline fuel cells.     

Crystal Transformation and Development of Tensile Properties upon Drawing of Poly(L-lactic acid) by Solid-State Coextrusion: Effects of Molecular Weight

Melt-crystallized films of poly(L -lactic acid) (PLLA) with M_v in the range of 3.8 ∼ 46 × 10⁴ consisting of α-form crystals were uniaxially drawn by solid-state coextrusion. The effects of M_v, extrusion draw ratio (EDR), and extrusion temperature (T_ext) on the crystal/crystal transformation from α- to β-form crystals and the resultant tensile properties of drawn products were studied. The crystal transformation proceeded with EDR and more rapidly for the higher M_v's. Furthermore, the crystal transformation proceeded most rapidly with EDR at a T_ext around 130 °C, independently of the M_v's. As a result of the optimum combination of processing variables influencing the the crystal transformation (M_v, T_ext, and drawability), highly oriented films consisting of β-form crystals alone were obtained by coextrusion of higher M_v samples at T_ext's slightly below the melting temperature (150 ∼ 170 °C) and at higher EDR's > 11. Both the tensile modulus and strength increased rapidly with EDR. The modulus at a given EDR was slightly higher for the samples with higher M_v's. In contrast, the strength at a given EDR was remarkably higher for the higher M _v's. The highest tensile modulus of 8.0 GPa and strength of 500 MPa were obtained with the sample of the highest M_v of 46 × 10⁴ coextruded at 170 °C to the highest EDR of 14.     

Unity‐Order Nonlinear Optical Index Change in Epsilon‐Near‐Zero Composite Materials of Gain Media and Metal Nanoparticles

This work reports giant optical nonlinearity of active gain composites containing metal nanoparticles. In the epsilon‐near‐zero regime, the effective index of the composite strongly depends on the magnitude of host material's saturable gain and one can obtain unity‐order nonlinear optical index change for the pump with gain saturation intensity. For pump intensity of about 100 kW/cm², the nonlinear refractive index (the refractive index change per unit pump intensity) reaches 10^?5 cm²/W, which is 6–8 orders‐of‐magnitude larger than the records recently obtained in epsilon‐near‐zero bulk materials. If the gain value of the host medium is slightly larger than a critical value, such large optical nonlinearity can be obtained without loss or even accompanying with amplification. The proposed materials also have the advantage of wide tunability of operating wavelength range from visible to infrared by changing the gain value of the host and the shape parameters and filling factors of metal nanoparticles.     

Biodegradable ultra high strength poly(L-lactide) rods for bone fixation

The hydrostatic molecular orientation technique was used to explore the highest mechanical improvements achievable for poly-L-lactide (PLLA). The mechanical attributes of these materials designed for bone fracture fixation devices, i.e. bending strength and modulus were measured and compared with those prepared by stretching method. The starting samples were prepared by conventional melt extrusion at 200 °C followed by hydrostatic extrusion at 140 °C using glycerin filled extruder. Uniaxially stretched rods were prepared by drawing in silicon oil at 120 °C. The physical properties of these rods are inadequate as mechanical supports in the dynamic healing process of the bone. Moreover, they underwent a marked strength deterioration when immersed in aqueous buffered solution for 90 days. On the other hand, the hydrostatic extrusion technique produced rods with progressively higher bending strength that showed only a small drop after 90 days hydrolytic degradation. Micrographs suggested a superior molecular orientation and packing, which could be associated with the improved performance. The hydrostatic extrusion technique proved to be a safe and effective approach for strengthening biodegradable polymeric materials for dynamic mechanical support in orthopedic medical devices.