159 research outputs found
Constraining the position of the knee in the galactic cosmic ray spectrum with ultra-high-energy diffuse -rays
The diffuse -ray emission was measured up to TeV by the
Tibet-AS experiment recently. Assuming that it is produced by the
hadronic interaction between cosmic ray nuclei and the interstellar medium, it
requires that the cosmic ray nuclei should be accelerated well beyond PeV
energies. Measurements of the cosmic ray spectra for different species show
diverse results at present. The Tibet experiments showed that the spectrum of
proton plus helium has an early knee below PeV. If this is correct, the diffuse
-ray emission would suggest an additional component of Galactic cosmic
rays above PeV energies. This second component may originate from a source
population of so-called PeVatrons revealed by recent ultra-high energy
-ray observations, and could contribute to the cosmic ray fluxes up to
the energy of the second knee. On the other hand, the KASCADE measurement
showed that the knee of protons is higher than PeV. In this case, the diffuse
-rays observed by Tibet-AS can be well accounted for by only
one cosmic ray component. These two scenarious (ie. the Tibet and KASCADE
knees) could be distinguished by the spectral structures of diffuse
-rays and cosmic ray nuclei. Future measurements of spectra of
individual nuclei by HERD and LHAASO experiments and diffuse -rays by
LHAASO can jointly constrain these two scenarios.Comment: 9 pages,4 figures. accepted by Ap
Nearby SNR: a possible common origin to multi-messenger anomalies in spectra, ratios and anisotropy of cosmic rays
The multi-messenger anomalies, including spectral hardening or excess for
nuclei, leptons, ratios of and B/C, and anisotropic reversal, were
observed in past years. AMS-02 experiment also revealed different spectral
break for positron and electron at 284 GeV and beyond TeV respectively. It is
natural to ask whether all those anomalies originate from one unified physical
scenario. In this work, the spatially-dependent propagation (SDP) with a nearby
SNR source is adopted to reproduce above mentioned anomalies. There possibly
exists dense molecular cloud(DMC) around SNRs and the secondary particles can
be produced by pp-collision or fragmentation between the accelerated primary
cosmic rays and DMC. As a result, the spectral hardening for primary, secondary
particles and ratios of and can be well reproduced. Due to the
energy loss at source age of 330 kyrs, the characteristic spectral break-off
for primary electron is at about 1 TeV hinted from the measurements. The
secondary positron and electron from charged pion take up energy from
their mother particles, so the positron spectrum has a cut-off at 250
GeV. Therefore, the different spectral break for positron and electron together
with other anomalies can be fulfilled in this unified physical scenario. More
interesting is that we also obtain the featured structures as spectral
break-off at 5 TV for secondary particles of Li, Be, B, which can be served to
verify our model. We hope that those tagged structures can be observed by the
new generation of space-borne experiment HERD in future.Comment: 16 pages, 12 figure
Statistically study the optimal local sources for cosmic ray nuclei and electron
The local sources, such as Geminga SNR, may play important role for the
anomaly of proton, electron and anisotropy in the past works. In fact, there
exists twelve SNRs around solar system within kpc. One question is that can
other SNRs also possibly contribute the spectra of nuclei and electron and
explain the special structure of anisotropy? In this work, under the
spatial-dependent propagation, we systematically study the contribution of all
local SNRs within 1 kpc around solar to the spectra of nuclei and electron, as
well as the energy dependence of anisotropy. As a result, only Geminga,
Monogem, and Vela SNRs have quantitive contribution to the nuclei and electron
spectra and anisotropy. Here, Geminga SNR is the sole optimal candidate and
Monogem SNR is controversial due to the tension of anisotropy between model
calculation and observations. The Vela SNR contributes a new spectral structure
beyond TeV energy, hinted by HESS, VERITAS, DAMPE and CALET measurements. More
interesting is that the electron anisotropy satisfies the Fermi-LAT limit below
TeV energy, but rises greatly and reaches at several TeV. This new
structure will shed new light to check our model. We hope that the new
structure of electron spectrum and anisotropy can be observed by space-borne
DAMPE and HERD and ground-based HAWC and LHAASO experiments in the near future.Comment: 11 pages, 8 figures, accepted by AP
The role of spinal GABAB receptors in cancer-induced bone pain in rats
Cancer-induced bone pain (CIBP) remains a major challenge in advanced cancer patients due to our lack of understanding of its mechanisms. Previous studies have demonstrated the vital role of GABAB receptors (GABABRs) in regulating nociception and various neuropathic pain models have shown diminished activity of GABABRs. However, the role of spinal GABABRs in CIBP remains largely unknown. In this study, we investigated the specific cellular mechanisms of GABABRs in the development and maintenance of CIBP in rats. Our behavioral results show that both acute and chronic intrathecal treatment with baclofen, a GABABR agonist, significantly attenuated CIBP-induced mechanical allodynia and ambulatory pain. The expression levels of GABABRs were significantly decreased in a time-dependent manner and colocalized mostly with neuron and a minority with astrocyte and microglia. Chronic treatment with baclofen restored the expression of GABABRs and markedly inhibited the activation of cAMP-dependent protein kinase (PKA) and the cAMP-response element-binding protein (CREB) signaling pathway
The Impacts of Emission Control and Regional Transport on PM2.5 Ions and Carbon Components in Nanjing during the 2014 Nanjing Youth Olympic Games
Highly time-resolved measurements of water soluble ions, organic and elemental carbon concentrations in the particle diameter size range D-p <2.5 mu m (PM2.5) were performed at a downwind urban site in Nanjing in the western part of the Yangtze River Delta (YRD) in eastern China during the 2014 Youth Olympic Games (YOG). In this study, we discuss the impacts of emission control in Nanjing and the surrounding areas during the YOG and regional/long-range transport on PM2.5 pollution in Nanjing. The average concentrations of NO3-, SO42-, NH4+ were 12.1 +/- 9.9, 16.5 +/- 9.2, 9.0 +/- 5.4 mu g m(-3) during the YOG, and increased 34.3%, 53.7%, 43.9% after the YOG, respectively. The control of construction or on-road soil dust and control of industry led to the decrease of Ca2+ concentration by 55% and SO2 concentration by 46%. However, SO42- concentrations remained at relatively high levels, suggesting a significant impact of regional pollution to secondary fine particles in Nanjing. Strong correlations between OC and EC were observed during and after the YOG. A higher percentage (41%) of secondary organic carbon in Nanjing during the YOG periods was consistent with high potential photochemistry and low contributions from coal combustion. Lagrangian dispersion modelling results proved that the city clusters along the Nanjing and Shanghai axis were the major source region for high PM2.5 pollution in upwind Nanjing. This work shows that short-term strict control measures could improve the air quality, especially that affected by the primary pollutants; however, regional collaborative control strategy across administrative borders in the YRD is needed for a substantial improvement of air quality.Peer reviewe
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