Probing Cosmic-ray Propagation with TeV Gamma Rays from the Sun Using the HAWC Observatory

Cosmic rays in the inner solar system are subject to deflection by both the geomagnetic and interplanetary magnetic fields, and simultaneously interact with the Sun's photosphere resulting in the production of gamma rays. This phenomenon can be studied by observing the deficit ("shadow") in the cosmic ray flux from the direction of the Sun and searching for an excess photon signal above the isotropic background. The High Altitude Water Cherenkov (HAWC) Observatory in Mexico has been taking data on the solar disk at TeV energies since the end of 2014. We present our first efforts to estimate the luminosity of TeV gamma rays from the Sun which can be used to place limits on the production mechanisms, including astrophysical processes and beyond the standard model predictions.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution

Simultaneous Transmission and Reception: Algorithm, Design and System Level Performance

Full Duplex or Simultaneous transmission and reception (STR) in the same frequency at the same time can potentially double the physical layer capacity. However, high power transmit signal will appear at receive chain as echoes with powers much higher than the desired received signal. Therefore, in order to achieve the potential gain, it is imperative to cancel these echoes. As these high power echoes can saturate low noise amplifier (LNA) and also digital domain echo cancellation requires unrealistically high resolution analog-to-digital converter (ADC), the echoes should be cancelled or suppressed sufficiently before LNA. In this paper we present a closed-loop echo cancellation technique which can be implemented purely in analogue domain. The advantages of our method are multiple-fold: it is robust to phase noise, does not require additional set of antennas, can be applied to wideband signals and the performance is irrelevant to radio frequency (RF) impairments in transmit chain. Next, we study a few protocols for STR systems in carrier sense multiple access (CSMA) network and investigate MAC level throughput with realistic assumptions in both single cell and multiple cells. We show that STR can reduce hidden node problem in CSMA network and produce gains of up to 279% in maximum throughput in such networks. Finally, we investigate the application of STR in cellular systems and study two new unique interferences introduced to the system due to STR, namely BS-BS interference and UE-UE interference. We show that these two new interferences will hugely degrade system performance if not treated appropriately. We propose novel methods to reduce both interferences and investigate the performances in system level.Comment: 20 pages. This manuscript will appear in the IEEE Transactions on Wireless Communication

Salt-induced changes in germination and vegetative stages of Anethum graveolens L.

The aim of this experiment was to determine the response of dill (Anethum graveolens L.) to salt stress during germination and vegetative stages. In the first stage, response of dill seeds germination to levels of salinity (0, 50, 75 and 100 mM) was investigated. In the second stage, influence of salt stress on physiological and biochemical parameters in dill seedlings were investigated. Results showed germination rate and percentage, radical, plumule length and dry weight decreased significantly with the increase of salinity levels. Effect of salt stress on amount of chlorophyll a, b and total was significant. Results indicated that, amount of proline, total soluble carbohydrates and proteins and catalase (CAT) activity in shoots and roots significantly increased with the increase of salinity. These results showed that dill maintained higher carbohydrates, proteins, proline and activity of CAT under salt stress and these traits could have partially to its salt tolerance