The Spatial Distribution Of OH And CN Radicals In The Coma Of Comet Encke

Multiple potential parent species have been proposed to explain CN abundances in comet comae, but the parent has not been definitively identified for all comets. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Comet Encke is the shortest orbital period (3.3 years) comet known and also has a low dust-to-gas ratio based on optical observations. Observations of CN were obtained from 2003 October 22 to 24, using the 2.7 m telescope at McDonald Observatory. To determine the parent of CN, the classical vectorial model was modified by using a cone shape in order to reproduce Encke's highly aspherical and asymmetric coma. To test the robustness of the modified model, the spatial distribution of OH was also modeled. This also allowed us to obtain CN/OH ratios in the coma. Overall, we find the CN/OH ratio to be 0.009 +/- 0.004. The results are consistent with HCN being the photodissociative parent of CN, but we cannot completely rule out other possible parents such as CH(3)CN and HC(3)N. We also found that the fan-like feature spans similar to 90 degrees, consistent with the results of Woodney et al..NASAOffice of the Vice President for Research and Economic Development at Mississippi State UniversityMcDonald Observator

Amorphous Sb2Te3 nanowires: Synthesis, characterization and size-dependent phase transition behavior

Understanding the phase transition behavior of phase-change (PC) material with respect to the scaling effect is essential for the application of PC materials. Among all the PC materials, SbTe binary plays a significant role in the well-known Ge-Sb-Te system. Here we have used an unconventional and cost-effective method to fabricate a wide range of prototypical Sb2Te3 amorphous nanowires (18–220 nm in diameter) using templated electrodeposition. Compositional, morphological, and structural characterization of the amorphous nanowires were performed, and the crystallization temperature of in-template nanowires was measured using a four-probe resistivity meter. We report that the crystallization temperature of amorphous Sb2Te3 nanowires can be tuned with respect to the diameter of the nanowires and a significant increase was observed for the nanowires with diameters ≤35 nm. Our study sheds light on the size-dependent phase transition behavior of PC NWs with implications for further advancement of the PC memory technology