The bulk Lorentz factors of Fermi-LAT GRBs

The Lorentz factor (LF) of gamma-ray burst (GRB) ejecta may be constrained by observations of high-energy (HE) spectral attenuation. The recent Fermi-LAT observations of prompt GeV emission from several bright GRBs have leaded to conclusions of unexpectedly large LFs, $\Gamma>10^3$. Here we revisit this problem with two main concerns. (1) With one-zone assumption where all photons are assumed to be generated in the same region (radius) and time, we {\em self-consistently} calculate the $\gamma\gamma$ optical depth by adopting a target photon spectrum with HE cutoff. We find that this might be important when the GRB LF is below a few hundreds. (2) Recent Fermi-LAT observations suggest that the bulk MeV-range and HE (\ga100 MeV) emission may arise from different regions. We then consider a two-zone case where HE emission is generated in much larger radii than that of the MeV-range emission. We find that the HE emission may be mainly attenuated by MeV-range emission and that the attenuated HE spectrum does not show an exponential spectral cutoff but a slight steepening. This suggests that there may be no abrupt cutoff due to $\gamma\gamma$ attenuation if relaxing the one-zone assumption. By studying the spectra of three bright Fermi-LAT GRBs 080916C, 090510 and 090902B, we show that a bulk LF of\textbf{ $\Gamma\sim600$ }can be consistent with observations in the two-zone case. Even lower LFs can be obtained in the multi-zone case.Comment: 8 pages, a schematic figure added, the other 5 figures updated, ApJ, in pres

A study on the interaction of Alzheimer's disease beta amyloid protein with cultured mouse neuroblastoma cell line NB41A3

Thesis (Ph.D.) University of Alaska Fairbanks, 1994The $\beta$ amyloid protein is the primary constituent of amyloid plaques in the brains of Alzheimer's disease patients. The generation of $\beta$ amyloid protein from $\beta$ amyloid precursor protein and its interaction with neuronal cells were studied in the mouse neuroblastoma cell line NB41A3. Immunoreactivity to the carboxyl terminal of the precursor protein was detected among the membrane proteins of these cells, indicating that $\beta$ amyloid precursor protein is produced by NB41A3 cells. Also amyloid precursor protein carboxyl terminal immunoreactivity was observed in the conditioned medium of the cells, demonstrating various cytosolic peptide fragments are secreted during the cellular processing of the $\beta$ amyloid precursor protein. Synthetic $\beta$ amyloid peptide was shown to negatively affect NB41A3 neuroblastoma cells as judged by decreasing cell numbers, decreasing amount of cell protein, and release of the cytosolic enzyme, lactic dehydrogenase, into the medium. At the ultrastructural level, internal damage to the nucleus could be observed. Synthetic $\beta$ peptide showed specific binding with neuroblastoma cells. The internalization of the $\beta$ peptide into the cells suggest a direct mechanism for $\beta$ amyloid protein toxicity in vivo. This research contributes to the knowledge of the processing of Alzheimer's disease $\beta$ amyloid precursor protein in NB41A3 cells and demonstrates that NB41A3 cell provides a practical in vitro model for studying the mechanism of Alzheimer's disease and amyloid toxicity

Secondary-electron radiation accompanying hadronic GeV-TeV gamma-rays from supernova remnants

The synchrotron radiation from secondary electrons and positrons (SEPs) generated by hadronic interactions in the shock of supernova remnant (SNR) could be a distinct evidence of cosmic ray (CR) production in SNR shocks. Here we provide a method where the observed gamma-ray flux from SNRs, created by pion decays, is directly used to derive the SEP distribution and hence the synchrotron spectrum. We apply the method to three gamma-ray bright SNRs. In the young SNR RX J1713.7-3946, if the observed GeV-TeV gamma-rays are of hadronic origin and the magnetic field in the SNR shock is $B\gtrsim 0.5$mG, the SEPs may produce a spectral bump at $10^{-5}-10^{-2}$eV, exceeding the predicted synchrotron component of the leptonic model, and a soft spectral tail at $\gtrsim 100$keV, distinct from the hard spectral slope in the leptonic model. In the middle-aged SNRs IC443 and W44, if the observed gamma-rays are of hadronic origin, the SEP synchrotron radiation with $B\sim 400 - 500 \mu$G can well account for the observed radio flux and spectral slopes, supporting the hadronic origin of gamma-rays. Future microwave to far-infrared and hard X-ray (>100keV) observations are encouraged to constraining the SEP radiation and the gamma-ray origin in SNRs.Comment: 9 pages, 5 figures and 1 table, MNRAS accepte

A new Perspective of student Ideological and Political Work Paradigm: Based on embodied Cognition

The concept of “paradigm” was put forward by American philosopher of science Thomas Kuhn, which has been widely used in various scientific researches. Under the influence of traditional cognitive science, the paradigm of students’ ideological and political work advocates the dualism of body and mind, pays attention to the cultivation of human spirit, and ignores or belfries the role of body in cognition, which has some drawbacks. The ideological and political paradigm of students from the perspective of embodied cognition adheres to the monism, advocates the integration of body, mind and mind, and has the characteristics of embodied, situational and experiential. It is a brand-new paradigm of students’ ideological and political work. In practice, this paradigm forms a new path of students’ ideological and political work, including investigation and analysis, content and way, participation and identification, complementation and guidance

Impact of the Desert dust on the summer monsoon system over Southwestern North America

The radiative forcing of dust emitted from the Southwest United States (US) deserts and its impact on monsoon circulation and precipitation over the North America monsoon (NAM) region are simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem) for 15 years (1995–2009). During the monsoon season, dust has a cooling effect (−0.90 W m<sup>−2</sup>) at the surface, a warming effect (0.40 W m<sup>−2</sup>) in the atmosphere, and a negative top-of-the-atmosphere (TOA) forcing (−0.50 W m<sup>−2</sup>) over the deserts on 24-h average. Most of the dust emitted from the deserts concentrates below 800 hPa and accumulates over the western slope of the Rocky Mountains and Mexican Plateau. The absorption of shortwave radiation by dust heats the lower atmosphere by up to 0.5 K day<sup>−1</sup> over the western slope of the Mountains. Model sensitivity simulations with and without dust for 15 summers (June-July-August) show that dust heating of the lower atmosphere over the deserts strengthens the low-level southerly moisture fluxes on both sides of the Sierra Madre Occidental. It also results in an eastward migration of NAM-driven moisture convergence over the western slope of the Mountains. These monsoonal circulation changes lead to a statistically significant increase of precipitation by up to ~40 % over the eastern slope of the Mountains (Arizona-New~Mexico-Texas regions). This study highlights the interaction between dust and the NAM system and motivates further investigation of possible dust feedback on monsoon precipitation under climate change and the mega-drought conditions projected for the future

Cardioprotective Effect of Sodium Ferulate in Diabetic Rats

Reactive oxygen species (ROS) play important roles in the occurrence and development in diabetic cardiomyopathy (DC). Ferulic acid is one of the ubiquitous compounds in diet. Sodium ferulate (SF) is its sodium salt. SF has potent free radical scavenging activity and can effectively scavenge ROS. The study investigated the effect of SF on cardioprotection in diabetic rats. The diabetic rats induced by streptozotocin (STZ) were treated with SF (110mg/kg) by gavage per day for 12 weeks. Results showed that the levels of nitric oxide (NO) and superoxide dismutase (SOD) activity in plasma and myocardium in SF-treated group were significantly higher than those in diabetic control group. The levels of malondialdehyde (MDA) in plasma and myocardium in SF-treated group were significantly lower than those in diabetic control group. Expression of connective tissue growth factor (CTGF) in myocardium in SF-treated group was apparently lower than that in diabetic control group. Compared with normal control group, electron micrographs of myocardium in diabetic control group showed apparently abnormality, while that was significantly ameliorated in SF-treated group. The study demonstrated that SF has a cardioprotective effect via increasing SOD activity and NO levels in plasma and myocardium, inhibiting oxidative stress in plasma and myocardium, and inhibiting the expression of CTGF in myocardium in diabetes rats