Evidence for GeV emission from the Galactic Center Fountain

The region near the Galactic center may have experienced recurrent episodes of injection of energy in excess of $\sim$ 10$^{55}$ ergs due to repeated starbursts involving more than $\sim$ 10$^4$ supernovae. This hypothesis can be tested by measurements of $\gamma$-ray lines produced by the decay of radioactive isotopes and positron annihilation, or by searches for pulsars produced during starbursts. Recent OSSE observations of 511 keV emission extending above the Galactic center led to the suggestion of a starburst driven fountain from the Galactic center. We present EGRET observations that might support this picture.Comment: 5 pages, 1 embedded Postscript figure. To appear in the Proceedings of the Fourth Compton Symposiu

A Study on anisotropy of cosmic ray distribution with a small array of water-cherenkov detectors

The study of the anisotropy of the arrival directions is an essential tool to investigate the origin and propagation of cosmic rays primaries. A simple way of recording many cosmic rays is to record coincidences between a number of detectors. We have monitored multi-TeV cosmic rays by a small array of water cherenkov detectors in Tehran(35 43 N, 51 20 E, 1200m a.s.l). More than 1.1*10^6 extensive air shower events were recorded. In addition to the Compton- Getting effect due to the motion of the earth in the Galaxy, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.Comment: 16 pages 9 figs and one tabl

Evidence for a Galactic gamma ray halo

We present quantitative statistical evidence for a $\gamma$-ray emission halo surrounding the Galaxy. Maps of the emission are derived. EGRET data were analyzed in a wavelet-based non-parametric hypothesis testing framework, using a model of expected diffuse (Galactic + isotropic) emission as a null hypothesis. The results show a statistically significant large scale halo surrounding the center of the Milky Way as seen from Earth. The halo flux at high latitudes is somewhat smaller than the isotropic gamma-ray flux at the same energy, though of the same order (O(10^(-7)--10^(-6)) ph/cm^2/s/sr above 1 GeV).Comment: Final version accepted for publication in New Astronomy. Some additional results/discussion included, along with entirely revised figures. 19 pages, 15 figures, AASTeX. Better quality figs (PS and JPEG) are available at http://tigre.ucr.edu/halo/paper.htm

Multi-messenger radio frequency and optical diagnostics of pulsed laser ablation processes

: In this report, a novel non-contact, non-invasive methodology for near and quasi real-time measurement of the structuring of metal surfaces using pulsed laser ablation is described. This methodology is based on the use of a multi-messenger data approach using data from Optical Emission Spectroscopy (OES) and Radio Emission Spectroscopy (RES) in parallel. In this research, radio frequency (RF) emission (in the range of 100–400 MHz) and optical emission (200–900 nm) were investigated and acquired in real-time. The RES and OES data were post-processed and visualized using heat maps, and, because of the large data sets acquired particularly using in RES, Principal Component Analysis (PCA) statistics were used for data analysis. A comparison between in-process RES-OES data and post-process 3D images of the different ablated holes generated by a picosecond laser with different powers (1.39 W, 1.018 W, and 0.625 W) on aluminum (Al) and copper (Cu) was performed. The real-time time-series data acquired using the Radio and Optical Emission Spectroscopy technique correlate well with post-process 3D microscopic images. The capability of RES-OES as an in operando near real-time diagnostic for the analysis of changes of ablation quality (cleanliness and symmetry), and morphology and aspect ratios (including the diameter of ablated holes) in the process was confirmed by PCA analysis and heat map visualization. This technique holds great promise for in-process quality detection in metal micromachining and laser-metal base manufacturing

Oxidation behavior and microstructural evolution of Ti-6Al-4V and Ti-6Al-4V-1B sheet

A direct comparison between the oxidation behavior of Ti-6Al-4V and Ti-6Al-4V + 1B has been conducted to elucidate whether the addition of boron to Ti-6Al-4V impacts the oxidation behavior. Industrially prepared sheet of Ti-6Al-4V and Ti-6Al-4V + 1B were oxidized at temperatures between 650 and 950 °C for holding times of 25 and 50 h. Weight-gain measurements and characterization of surface and near-surface microstructures showed that the addition of 1 wt% B increased the material’s oxidation resistance. Additionally, the ingress of oxygen tends to decrease the solubility of other alloying species in α-Ti and leads to the formation of a distinctive and atypical microstructure with a distinct morphology