Wolframite-structure ZnTi0.6Sn0.4Nb2O8 was firstly prepared by the conventional solid-state method. X-ray diffraction patterns showed that the samples exhibited wolframite structure instead of ...ixiolite-structure of ZnTiNb2O8. Microwave dielectric properties of ZnTi0.6Sn0.4Nb2O8 ceramics exhibited a significant dependence on sintering characteristics and crystal structure. The phase transition in ZnTi0.6Sn0.4Nb2O8 ceramics played an important role in reducing dielectric loss. In addition, the bond energy of ceramics was also reported for the first time to analyze intrinsic loss. Typically, the ZnTi0.6Sn0.4Nb2O8 ceramics sintered at 1200°C for 4h exhibited excellent microwave dielectric properties with εr=24.61, Q·f =69,500GHz and τf=−2.67ppm/°C.
•Wolframite structure ZnTi0.6Sn0.4Nb2O8 was firstly prepared at 1200°C for 4h.•The microwave properties were εr=24.61, Q·f =69,500GHz and τf=−2.67ppm/°C.•The bond energy was used to characterize the intrinsic loss of ZnTi0.6Sn0.4Nb2O8.
The tetragonal-structured CoTiNb
2
O
8
was prepared by the conventional solid-state method. Morphology, crystal structure and microwave dielectric properties of the ceramics were investigated by ...means of scanning electron microscope and X-ray diffraction. Single-phase CoTiNb
2
O
8
could be obtained in the temperature range of 1100–1200 °C with the space group of P42/mnm. The dielectric constant and quality factors gradually increased with the increase of apparent density. The τ
f
values were shifted toward zero with the increase of sintering temperature. Complex bond theory was reported for the first time to characterize the correlations between crystal structure and microwave dielectric properties. Typically, the saturated samples sintered at 1150 °C exhibited excellent microwave properties with
ε
r
value of 66.41, Q·
f
value of 10,153 GHz and τ
f
value of 25.56 ppm/°C.
Aims.We calculate the attenuation of very high energy γ rays from Galactic sources.Methods.A recent calculation of the Galactic interstellar radiation field shows that the infra-red radiation ...background near the Galactic Center is very intense. The attenuation of very high energy γ rays by this radiation is strong and occurs at lower energies than previously thought.Results.Our result shows that the cutoff of the high energy γ ray spectrum begins at about 20 TeV and reaches about 10% for 50 TeV γ rays.
We report the observation of a very high energy gamma -ray source whose position is coincident with HESS J1841-055. This source has been observed for 4.5 years by the ARGO-YBJ experiment from 2007 ...November to 2012 July. Its emission is detected with a statistical significance of 5.3 standard deviations. Parameterizing the source shape with a two-dimensional Gaussian function, we estimate an extension (ProQuest: Formulae and/or non-USASCII text omitted), which is consistent with the HESS measurement. The observed energy spectrum is dN/dE = (9.0 + or - 1.6) x 10 super(-13)(E/5 TeV) super(-2.32+ or -0.23) photons cm super(-2) s super(-1) TeV super(-1), in the energy range 0.9-50 TeV. The integral gamma -ray flux above 1 TeV is 1.3 + or - 0.4 Crab, which is 3.2 + or - 1.0 times the flux derived by HESS. The differences in the flux determination between HESS and ARGO-YBJ and possible counterparts at other wavelengths are discussed.
The search for gamma-ray burst (GRB) emission in the energy range of 1-100 GeV in coincidence with the satellite detection has been carried out using the Astrophysical Radiation with Ground-based ...Observatory at YangBaJing (ARGO-YBJ) experiment. The high-altitude location (4300 m a.s.l.), the large active surface (~6700 m super(2) of Resistive Plate Chambers), the wide field of view (~2 sr, limited only by the atmospheric absorption), and the high duty cycle (>86%) make the ARGO-YBJ experiment particularly suitable to detect short and unexpected events like GRBs. With the scaler mode technique, i.e., counting all the particles hitting the detector with no measurement of the primary energy and arrival direction, the minimum threshold of ~1 GeV can be reached, overlapping the direct measurements carried out by satellites. During the experiment lifetime from 2004 December 17 to 2013 February 7, a total of 206 GRBs occurring within the ARGO-YBJ field of view (zenith angle theta < or =, slant 45degrees) have been analyzed. This is the largest sample of GRBs investigated with a ground-based detector. Two light curve models have been assumed and since in both cases no significant excess has been found, the corresponding fluence upper limits in the 1-100 GeV energy region have been derived, with values as low as 10 super(-5) erg cm super(-2). The analysis of a subset of 24 GRBs with known redshift has been used to constrain the fluence extrapolation to the GeV region together with possible cutoffs under different assumptions on the spectrum.
A novel series of rock salt structured (1-x)Li2ZrO3-xMgO ceramics were prepared via the conventional solid state method. The tetragonal-cubic phase transition can be observed in the case of ...0.5 ≤ x ≤ 0.6, which has been testified by the results of XRD and SEM-EDS. Relatively dense and homogeneous microstructure can be obtained for all the compositions sintered at 1500 °C. With the x value increasing from 0.5 to 0.8, the relative permittivity linearly decreases from 16.50 to 12.65, and the τf value decreases from ∼−10 ppm/°C to ∼−35 ppm/°C. The addition of MgO stabilizes the crystal structure and increases the bond energies in Li2ZrO3-MgO system, so there is an upward tendency in Q·f values from ∼77,000 GHz to ∼166,000 GHz. Typically, the Li2Mg4ZrO7 ceramics sintered at 1500 °C possesses excellent properties with εr = 12.65, Q·f = 165,924 GHz and τf=-34.66 ppm/°C, which makes these materials good candidates for microwave devices.
Direct deposition of a uniform and high-quality Bi
2
Se
3
thin film on a graphene film (layer controlled) is performed using a catalyst-free vapor deposition system in a Se-rich environment. The ...Se-rich environment is utilized to fill the Se vacancies and is beneficial to achieving the uniform chemical composition of the product. The layers of graphene can be controlled easily and precisely by the transfer times. Besides the graphene film, the morphology of the product is sensitive to the growth parameters (temperature of the substrate, growth time and gas flow). By controlling the growth parameters, we can also grow a crystal Bi
2
Se
3
plate on the graphene/SiO
2
/Si substrate. Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction confirm the presence of uniform and high-quality Bi
2
Se
3
.
Direct deposition of a uniform and high-quality Bi
2
Se
3
thin film on a graphene film (layer controlled) is performed using a catalyst-free vapor deposition system in a Se-rich environment.
•First time application of hybrid cybernetic model in mammalian cell culture.•Demonstrate the scalability and availability of HCM in more complex system.•Perfect simulation of mammalian cell ...culture.•Precise prediction of mammalian cell culture.
A dynamic model called hybrid cybernetic model (HCM) based on structured metabolic network is established for simulating mammalian cell metabolism featured with partially substitutable and partially complementary consumption patterns of two substrates, glucose and glutamine. Benefiting from the application of elementary mode analysis (EMA), the complicated metabolic network is decomposed into elementary modes (EMs) facilitating the employment of the hybrid cybernetic framework to investigate the external and internal flux distribution and the regulation mechanism among them. According to different substrate combination, two groups of EMs are obtained, i.e., EMs associated with glucose uptake and simultaneous uptake of glucose and glutamine. Uptake fluxes through various EMs are coupled together via cybernetic variables to maximize substrate uptake. External fluxes and internal fluxes could be calculated and estimated respectively, by the combination of the stoichiometrics of metabolic networks and fluxes through regulated EMs. The model performance is well validated via three sets of experimental data. Through parameter identification of limited number of experimental data, other external metabolites are precisely predicted. The obtained kinetic parameters of three experimental cultures have similar values, which indicates the robustness of the model. Furthermore, the prediction performance of the model is successfully validated based on identified parameters.
Ni0.5Zn0.5Fe2O4 is one of the traditional microwave absorbing materials, and it has attract the focus of the whole world in the past years. The composites behave well in absorbing areas due to its ...coexistence of dielectric property and ferrimagnetism. The graphene is one of the new absorbing materials and it has been used in varies areas due to its excellent electrical conductivity, thermal conductivity and mechanical properties. In the work, the Ni0.5Zn0.5Fe2O4 nanoparticles were surficiently compounded with the reduced graphene (RGO), and the microstructure and microwave absorbing performance of the composites were characterized. Consequently, the results indicated that the as-prepared materials perform well in microwave absorption area.
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