The gas response to a proposed spiral stellar pattern for our Galaxy is presented here as calculated via 2D hydrodynamic calculations utilizing the ZEUS code in the disk plane. The locus is that found by Drimmel (2000) from emission profiles in the K band and at 240 μm. The self-consistency of the stellar spiral pattern was studied in previous work (see Martos et al. 2004). It is a sensitive function of the pattern rotation speed, Ωp, among other parameters which include the mass in the spiral and its pitch angle. Here we further discuss the complex gaseous response found there for plausible values of Ωp in our Galaxy, and argue that its value must be close to 20 km s-l kpc-1 from the strong self-consistency criterion and other recent, independent studies which depend on such parameter. However, other values of Ωp that have been used in the literature are explored to study the gas response to the stellar (K band) 2-armed pattern. For our best fit values, the gaseous response to the 2-armed pattern displayed in the K band is a four-armed pattern with complex features in the interarm regions. This response resembles the optical arms observed in the Milky Way and other galaxies with the smooth underlying two-armed pattern of the old stellar disk populations in our interpretation. The complex gaseous response appears to be related to resonances in stellar orbits. Among them, the 4:1 resonance is paramount for the axisymmetric Galactic model employed, and the set of parameters explored. In the regime seemingly proper to our Galaxy, the spiral forcing appears to be marginally strong in the sense that the 4:1 resonance terminates the stellar pattern, despite its relatively low amplitude. In current work underway, the response for low values of Ωp tends to remove most of the rich structure found for the optimal self-consistent model and the gaseous pattern is ring-like. For higher values than the optimal, more features and a multi-arm structure appears.

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a: ∼0.1 ) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

Schools in developing countries such as China are faced with many challenges when it comes to K- 12 technology integration into classrooms and curricula. The Global Education Model School (GEMS) project aims to help schools overcome these challenges. In this paper we first examine the outcomes of the GEMS program in China, on the basis of which we propose a model for facilitating computer technology integration in K-12 schools China. It is the contribution of this new model to move the emphasis from support of teachers from the international and national levels to teacher collaboration at the school and regional levels. Through the use of technology, communities of teachers can be established, providing an enhanced and more sustainable change management process. The ultimate goal of such an improved change management strategy is to help expand technology integration in China's K-12 classrooms.