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[en] Carbon nanotube (CNT) is considered as a kind of potential adsorbent because of its large surface area, uniform micropores and unique physicochemical properties. The adsorption performance of ammonia on the packed multi-walled carbon nanotubes (MWCNTs) were studied in this paper. Firstly, the packed MWCNTs were characterized by the scanning electron microscope (SEM) and transmission electron microscopy (TEM). Secondly, the effect of working pressure and adsorbent temperature on the adsorption capacity of ammonia by the packed MWCNTs was investigated. Thirdly, Langmuir and Freundlich models were used to analyze the equilibrium adsorption data and the adsorption kinetics was also discussed using a classical gas diffusion model. The Freundlich isotherm model could elucidate well the adsorption of ammonia on the MWCNTs when compared to the Langmuir equation. The research results showed that the equilibrium adsorption amount of ammonia by the MWCNTs varied between 22.69 and 90.05 mg/g_C_N_T at the adsorbent temperature of 25–35 °C and working pressure of 0.368–0.744 MPa. It seems that the pure MWCNT is not appropriate to act as the adsorbent for the solid–gas adsorption refrigeration due to its low adsorption capacity. However, our research indicates that the MWCNTs can be used as additive to some other chemical adsorbents to improve their heat transfer characteristics. - Highlights: • Adsorption performance of ammonia on packed MWCNTs was studied. • Effects of working pressure and temperature on the adsorption capacity were investigated. • Adsorption equilibrium data and kinetics of ammonia on MWCNTs were analyzed. • Equilibrium adsorption amount of ammonia varied 22.69–90.05 mg/g_C_N_T at different temperatures and pressures
[en] This paper deals with the preparation and antioxidation of polysaccharide from Porphyra haitanensis. The ratio of water to raw material, extraction temperature and extraction time were taken in sequence as independent variables in single factor test, and polysaccharide yield as response value. Using Box-Benhnken central combination experimental design principles and response surface methodology, interactions of variables and their influence on polysaccharide yield of P. haitanensis were studied and the prediction model of quadratic polynomial regression equation was inferred by simulation, in which the optimum parameters for preparing polysaccharide from P. haitanensis were 88.4°C of extraction temperature, 1.97 h of extraction time and 40:1 (ml/g) of ratio of water to raw material, and polysaccharide of 15.19 % in yield from P. haitanensis was verified after two parallel test. Furthermore, the polysaccharide of P. haitanensis showed good antioxidant capacity which could be used as potential natural antioxidant products in food additives industries. (author)
[en] A series of Mn-site doping samples La2/3Ca1/3Mn1-xCoxO3(0 ≤x ≤ 0.15) with an excellent single phase structure have been prepared. The magnetic and transport properties of this system have been systematically investigated. The Curie temperature TC decreases gradually and the temperature range of transition becomes wider with the increase of x. The abnormal transport properties induced by Co were doping characterized by the resistivity behavior of double peaks and low temperature minimum.
[en] Using a large pressure-jump apparatus and Bridgman anvils, the Grueneisen parameters of iron and copper were measured under high pressures of 4.58-7.49 GPa and 4.40-6.25 GPa, respectively. Substitution of ΔT/ΔP for ∂T/∂P at median pressure is strictly justified and the Grueneisen parameter at the median pressure was determined by a modified thermodynamic relationship γ (Pm) = [Ks(Pm)/T(Pm)](ΔT/ΔP), where Pm indicates the median pressure, and adiabatic correction of the temperature change was completed through analysing the experimental data. The new γ values obtained are reconcilable with previous reports, and their tendency with pressure is also in good agreement with the previous work. The results suggest that the improved method is reliable for measurements of the Grueneisen parameter at high pressure, and is promising for such measurements to the higher pressure range
[en] A magnetic method is presented to characterize the concentration of point defects in silicon carbide. In this method, the concentration of common charged point defects, which is related to the density of paramagnetic centers, is determined by fitting the paramagnetic component of the specimen to the Brillouin function. Several parameters in the Brillouin function can be measured such as: the g-factor can be obtained from electron spin resonance spectroscopy, and the magnetic moment of paramagnetic centers can be obtained from positron lifetime spectroscopy combined with a first-principles calculation. To evaluate the characterization method, silicon carbide specimens with different concentrations of point defects are prepared with aluminum ion implantation. The fitting results of the densities of paramagnetic centers for the implanted doses of 1 × 10"1"4 cm"−"2, 1 × 10"1"5 cm"−"2 and 1 × 10"1"6 cm"−"2 are 6.52 × 10"1"4/g, 1.14 × 10"1"5/g and 9.45 × 10"1"4/g, respectively. The same trends are also observed for the S-parameters in the Doppler broadening spectra. It is shown that this method is an accurate and convenient way to obtain the concentration of point defects in 4H-SiC.
[en] Purpose: To investigate the role of nucleophosmin (NPM/B23) in radiation-induced chromosomal instability and apoptosis in human lymphoblastoid cells with different protein 53 (p53) status. Materials and methods: Wild type (wt) p53 TK6 and mutant type (mt) p53 WTK1 with or without short hairpin RNA (shRNA)-mediated silencing of NPM, TK6 with or without short interfering RNA (siRNA)-mediated silencing of p53 (p53i and NEGi) were irradiated with 4 Gy gamma-rays. Six to 48 h after irradiation, the index of apoptosis, chromosome aberration, cell cycle distribution and the levels of total NPM and phosphorylated-threonine 199 (pThr199) NPM proteins were measured. Cells in some dishes were treated with 10 μM Olomoucine (OLO) for 3 h before irradiation and remained in the medium after irradiation. Results: The rates of radiation-induced apoptosis in TK6 and TK6/NEGi were about 2-fold of those in WTK1 and TK6/p53i, while the frequencies of polyploidy in TK6 and TK6/NEGi were obviously lower than those in WTK1 and TK6/p53i. Moreover, after irradiation, pThr199 NPM levels increased significantly in WTK1 and TK6/p53i, and slightly increased in TK6 and TK6/NEGi, indicating that the increased level of pThr199 NPM was related to p53 status. When Thr199 hyperphosphorylation of NPM was inhibited by OLO or when NPM was knocked down, we found that radiation-induced apoptosis was more pronounced and polyploidy formation was reduced as compared with negative control while the magnitude of these changes in TK6 was obviously higher than that in WTK1, indicating that NPM has an antagonistic interaction with wt p53. Conclusions: NPM/B23 plays an important role in protecting cells from radiation-induced apoptosis and increasing polyploidy formation via either a p53 or non-p53 pathway. (authors)
[en] We synthesized a new phase from the B-C system, cubic BC4 (c-BC4), by direct transformation from graphitic phases at a pressure of 44 GPa and a temperature 2020 K in a laser-heated diamond anvil cell (DAC). Both x-ray diffraction and Raman spectroscopy confirm the presence of cubic BC4 from the sample recovered at ambient conditions. The zero-pressure lattice parameter of the c-BC4 calculated from diffraction peaks was found to be 3.587 A. The composition of the new phase is determined from electron microprobe (EMP) measurements. The value of the C/B ratio is around 4 (3.91 ± 0.26).
[en] Using amorphous Ni-Al-O (a-Ni-Al-O) thin film as the intermediate layer, poly-crystalline Er2O3 thin film was grown on a-Ni-Al-O/Si (p-type) via laser molecular beam epitaxy, forming the Er2O3/Ni-Al-O gate stack. It was found that the mean dielectric constant of the Er2O3/Ni-Al-O gate stack with an equivalent oxide thickness of 1.5 nm is about 17-23, the interfacial states density is about 3.16 x 1012 cm-2 and the stack gate leakage current density is as small as 4.1 x 10-6 A/cm2. Furthermore, The insertion of the Ni-Al-O thin film between the Er2O3 gate dielectric and p-Si substrate prevents the oxygen from being out-diffused, which significantly improved the stability of gate stack, showing that the Er2O3/Ni-Al-O gate stack thin film could be used as an ideal gate oxide layer for the future Metal Oxide Semiconductor Field Effect Transistors.