7,130 research outputs found
Detection of gamma-ray emission from the Coma cluster with Fermi Large Area Telescope and tentative evidence for an extended spatial structure
Many galaxy clusters have giant halos of non-thermal radio emission,
indicating the presence of relativistic electrons in the clusters. Relativistic
protons may also be accelerated by merger and/or accretion shocks in galaxy
clusters. These cosmic-ray (CR) electrons and/or protons are expected to
produce gamma-rays through inverse-Compton scatterings or inelastic
collisions respectively. Despite of intense efforts in searching for
high-energy gamma-ray emission from galaxy clusters, conclusive evidence is
still missing so far. Here we report the discovery of MeV gamma-ray
emission from the Coma cluster direction with an unbinned likelihood analysis
of the 9 years of {\it Fermi}-LAT Pass 8 data. The gamma-ray emission shows a
spatial morphology roughly coincident with the giant radio halo, with an
apparent excess at the southwest of the cluster. Using the test statistic
analysis, we further find tentative evidence that the gamma-ray emission at the
Coma center is spatially extended. The extended component has an integral
energy flux of in the
energy range of 0.2 - 300 GeV and the spectrum is soft with a photon index of
. Interpreting the gamma-ray emission as arising from CR proton
interaction, we find that the volume-averaged value of the CR to thermal
pressure ratio in the Coma cluster is about . Our results show that
galaxy clusters are likely a new type of GeV gamma-ray sources, and they are
probably also giant reservoirs of CR protons.Comment: 10 pages, 10 figures, Accepted by Physical Review D, more spatial
models for the gamma-ray emission are used, systematic checks on the results
are adde
catena-Poly[[chloridomercury(II)]-μ-1,4-diazabicyclo[2.2.2]octane-κ2 N:N′-[chloridomercury(II)]-di-μ-chlorido]
In the title coordination polymer, [Hg2Cl4(C6H12N2)]n, each HgII center within the chain is four-coordinated by one terminal Cl atom, two bridging μ2-Cl atoms, and one N-atom donor from a μ2-1,4-diazabicyclo[2.2.2]octane (μ2-daco) ligand in a distorted tetrahedral geometry. The daco ligand acts as an end-to-end bridging ligand and bridges adjacent HgII centers, forming a chain running along [001]. Weak C—H⋯Cl hydrogen-bonding interactions link the chains into a three-dimensional network. Comparison of the structural differences with previous findings suggests that the space between the two N donors, as well as the skeletal rigidity in N-heterocyclic linear ligands, may play an important role in the construction of such supramolecular networks
Angelica Sinensis promotes myotube hypertrophy through the PI3K/Akt/mTOR pathway
BACKGROUND: Angelica Sinensis (AS), a folk medicine, has long been used in ergogenic aids for athletes, but there is little scientific evidence supporting its effects. We investigated whether AS induces hypertrophy in myotubes through the phosphatidylinositol 3-kinase (PI3K)/Akt (also termed PKB)/mammalian target of the rapamycin (mTOR) pathway. METHODS: An in vitro experiment investigating the induction of hypertrophy in myotubes was conducted. To investigate whether AS promoted the hypertrophy of myotubes, an established in vitro model of myotube hypertrophy with and without AS was used and examined using microscopic images. The role of the PI3K/Akt/mTOR signaling pathway in AS-induced myotube hypertrophy was evaluated. Two inhibitors, wortmannin (an inhibitor of PI3K) and rapamycin (an inhibitor of mTOR), were used. RESULT: The results revealed that the myotube diameters in the AS-treated group were significantly larger than those in the untreated control group (P < 0.05). Wortmannin and rapamycin inhibited AS-induced hypertrophy. Furthermore, AS increased Akt and mTOR phosphorylation through the PI3K pathway and induced myotube hypertrophy. CONCLUSION: The results confirmed that AS induces hypertrophy in myotubes through the PI3K/Akt/mTOR pathway
A Compact Dual-Band Negative Group Delay Microwave Circuit
A compact dual-band negative group delay circuit (NGDC) is proposed. The proposed NGDC is composed of an open-circuited transmission line and two resistors connected by two transmission lines. The frequency ratio is controlled by the characteristic impedance of the transmission lines. To verify the design concept, a dual-band NGDC with the frequency ratio of n = 2 (Circuit A) and a broadband NGDC with n = 1.16 (Circuit B) are designed and fabricated. The measured group delay value of the Circuit A is -1.19 ns at the center frequencies of lower and upper bands. And the measured NGD bandwidth is 34.6% for the lower band and 16.5% for the upper band, in which the return loss and insertion loss are better than 16.9 dB and 18.2 dB, respectively. From the measurement results of Circuit B, a flat fractional NGD bandwidth of 19.8% with GD of (-1.58 ± 0.13) ns is obtained, in which the return loss and insertion loss are better than 23 dB and 32.5 dB, respectively
Measuring the Quality of Financial Electronic Payment System: Combined with Fuzzy AHP and Fuzzy TOPSIS
The study aims to apply Fuzzy AHP in TOPSIS to discuss the key factors that foster the success of current third-party online payment platforms. This study organized the quality measurements into four categories and eleven sub-categories. The AHP in TOPSIS is applied to calculate the weighted averages of all categories and sub-categories to measure the quality of third-party online payment platforms. This study finds that “safety quality” is the most emphasized category, “system quality” is the second, “communication quality” is the third, and “service quality” is the least emphasized
Evolutionary Stages and Disk Properties of Young Stellar Objects in the Perseus Cloud
We investigated the evolutionary stages and disk properties of 211 Young
stellar objects (YSOs) across the Perseus cloud by modeling the broadband
optical to mid-infrared (IR) spectral energy distribution (SED). By exploring
the relationships among the turnoff wave bands lambda_turnoff (longward of
which significant IR excesses above the stellar photosphere are observed), the
excess spectral index alpha_excess at lambda <~ 24 microns, and the disk inner
radius R_in (from SED modeling) for YSOs of different evolutionary stages, we
found that the median and standard deviation of alpha_excess of YSOs with
optically thick disks tend to increase with lambda_turnoff, especially at
lambda_turnoff >= 5.8 microns, whereas the median fractional dust luminosities
L_dust/L_star tend to decrease with lambda_turnoff. This points to an
inside-out disk clearing of small dust grains. Moreover, a positive correlation
between alpha_excess and R_in was found at alpha_excess > ~0 and R_in > ~10
the dust sublimation radius R_sub, irrespective of lambda_turnoff,
L_dust/L_star and disk flaring. This suggests that the outer disk flaring
either does not evolve synchronously with the inside-out disk clearing or has
little influence on alpha_excess shortward of 24 microns. About 23% of our YSO
disks are classified as transitional disks, which have lambda_turnoff >= 5.8
microns and L_dust/L_star >10^(-3). The transitional disks and full disks
occupy distinctly different regions on the L_dust/L_star vs. alpha_excess
diagram. Taking L_dust/L_star as an approximate discriminator of disks with
(>0.1) and without (<0.1) considerable accretion activity, we found that 65%
and 35% of the transitional disks may be consistent with being dominantly
cleared by photoevaporation and dynamical interaction respectively. [abridged]Comment: 31 pages, 13 figures, 2 tables. To appear in a special issue of RAA
on LAMOST science
Six lanthanide supramolecular frameworks based on mixed m-/p-hydroxybenzoic acid and 1,10-phenanthroline tectons: syntheses, crystal structures, and properties
To further explore the research of the coordination possibilities of lanthanide ions with m-/p-hydroxybenzoic acid isomers in the presence of chelating N-donor ligand 1,10-phenanthroline (phen), six lanthanide supramolecular frameworks based on 3- and 4-hydroxybenzoic acids, namely [Dy(m-L)(m-HL) (phen)]center dot H2O (1) (m-H2L = 3-hydroxybenzoic acid), [Ln(m-HL)(3)(phen)] (Ln = Gd for 2 and Tb for 3), [Ln(p-HL)(3)(phen)(H2O)] (Ln = Dy for 4, Gd for 5, and Tb for 6; p-H2L = 4-hydroxybenzoic acid), were synthesized and characterized. Structural analyses reveal that complex 1 has a two-dimensional (2-D) sheet structure while complexes 2 and 3 take the dinuclear structures in the 3-hydroxybenzoate derivatives. In the 4-hydroxybenzoate derivatives, complexes 4-6 are isostructural and incorporated by monomeric units. Finally, all the complexes exhibit three-dimensional (3-D) supramolecular frameworks (bcu net for I; bct nets for 2, and 4-6; hex net for 3) with the aid of abundant hydrogen bonding, pi center dot center dot center dot pi and C-H center dot center dot center dot pi interactions. The results reveal that the different positions of the-OH substituent and coordination modes of hydroxybenzoic acids adjust the final coordination networks. Moreover, the magnetic and luminescent properties of the complexes have also been investigated and discussed. (C) 2016 Elsevier Ltd. All rights reserved
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