Flame spread over solids in buoyant and forced concurrent flows: Model computations and comparison with experiments

A detailed three-dimensional concurrent flame spread model is tested and compared with three sets of experiments. The parameters varied include: gravity, flow velocity, pressure, oxygen mole fraction, and sample width. In buoyant flows (normal and partial gravities), the computed steady spread rate and flame profiles agree favorably with experiment. The predicted extinction limits are lower but can be improved. Comparison in forced concurrent flow in microgravity shows correct trends. The predicted steady spread rates are lower than the experimental ones if the flames are short but higher than the experimental ones if the flames are long. It is believed that the experimental flames may not have fully reached steady state at the end of the 5-s microgravity drops. Longer duration microgravity experiments in future will be needed to substantiate this belief.     

Microstructural and compositional studies of liquid-phase deposition derived PbTiO3 thin films on LaNiO3 substrates

PbTiO₃ thin films were successfully deposited on the LaNiO₃ (LNO) substrates by the liquid-phase deposition (LPD) method and post-annealing at various temperatures. The structure, morphology and composition of the films were investigated by some analytical techniques. The as-deposited films are amorphous and composed of densely packed spherical particles. The films with the grain size of 180 nm start to decompose and crystallize into perovskite structure at 450 °C and show a perovskite single phase with tetragonal structure after annealing at 650 °C. X-ray photoelectron spectroscopy (XPS) analysis reveals that the as-deposited film contains fluorine and carbon as major impurities. Fluorine could be completely eliminated by annealing at 650 °C in air.     

Intra-arterial application of magnetic nanoparticles for targeted thrombolytic therapy: A rat embolic model

Targeted delivery of thrombolytic drug to the site of emboli exhibits potential to greatly reduce hemorrhagic side effect. A rat embolic model with an easy access of a magnet was established for study of the efficacy of magnetic drug targeting. In anesthetized rats, a whole blood clot produced in vitro was injected from the right iliac artery and lodged in the left iliac artery. Intra-arterial infusion of recombinant tissue plasminogen activator (rt-PA) thereafter significantly reversed the iliac flow within 15 min. Placement of an NdFeB magnet above the left iliac artery caused magnetic nanoparticle retention against hemodynamic dragging force in the presence and absence of the clot. Our results suggest the feasibility of this rat embolic model for the study of magnetic targeted delivery of thrombolytic drugs.     

Immobilization of silver nanoparticles on silica microspheres

The silver nanoparticles (Ag NPs) have been immobilized onto silica microspheres through the adsorption and subsequent reduction of Ag⁺ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared through sol–gel processing; their surfaces were then functionalized using 3-mercaptopropyltrimethoxysilane (MPTMS). The major aims of this study were to immobilize differently sized Ag particles onto the silica microspheres and to understand the mechanism of formation of the Ag nano-coatings through the self-assembly/adsorption behavior of Ag NPs/Ag⁺ ions on the silica spheres. The obtained Ag NP/silica microsphere conglomerates were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). Their electromagnetic wave shielding effectiveness were also tested and studied. The average particle size of the obtained Ag NPs on the silica microsphere was found that could be controllable (from 2.9 to 51.5 nm) by adjusting the ratio of MPTMS/TEOS and the amount of AgNO₃.     

Barium ferrite particulates prepared by a salt-melt method

Barium ferrite particulates have been prepared by coprecipitation and calcination in a flux of NaCl-KCl. It was found that a flux containing more than 30 wt% KCl tends to seriously deteriorate the magnetic properties of resultant perticulates. The flux with 10 wt% KCl or less showed promising results. A Ba(CoZr)_0.75Fe_10.5O₁₉ particulate showed the best properties, i.e., a saturation magnetization of 68.5, a squareness ratio of 0.49, and a coercivity of 1280 Oe, when calcined in NaCl at 900°C for 4 h.     

Branching fractions for psi(2S)-to-J/psi transitions

We describe new measurements of the inclusive and exclusive branching fractions for psi(2S) transitions to J/psi using e(+)e(-) collision data collected with the CLEO detector operating at CESR. All branching fractions and ratios of branching fractions reported here represent either the most precise measurements to date or the first direct measurements. Indirectly and in combination with other CLEO measurements, we determine B(chi(cJ) --> gamma(J/psi)) and B[psi(2S) --> light hadrons].     

FDTD analysis of infrared radiative properties of microscale structure aluminum surfaces

Metallic triangular grating structures have a wide range of applications. This study focuses on the radiative properties of triangular grating structures of aluminum in the mid-infrared wavelength to determine if we can tailor the infrared radiative properties by designing special geometrical details into triangular grating surfaces. Fabrication of triangular gratings within the range of micron scale is very difficult. Therefore, the influences of slight geometry modification, generated by fabrication errors, on radiative properties of triangular gratings are mainly investigated. The electromagnetic wave scattering from such surfaces is predicted by solving Maxwell's equations using the finite-difference time-domain (FDTD) method. The results show that the spectral reflectance varies with the dimensions of triangular gratings, which is due to the excitation of surface wave by confirmation of the EM fields. It is found that the spectral reflectance can also be reduced by increasing the height of slight geometry modification. The effect of oblique incident wave state is also investigated. An optical vortex is found due to the coupling of surface waves, the oblique incident wave and the scattering waves. This study helps to gain a better understanding of the radiative properties of metallic triangular gratings with slight geometry modification and will have an impact on triangular grating processing.