M-type strontium hexaferrite (SrFe12O19) particles had been prepared by a modified chemical co-precipitation route. Structural and magnetic properties were systematically investigated. Rietveld ...refinement of X-ray powder diffraction results showed that the sample was single-phase with the space group of P63/mmc and cell parameter values of a=5.8751 A and c=23.0395 A. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 2 to 4 mum. The composition determined by energy dispersive spectroscopy is the stoichiometry of SrFe12O19. The ferrimagnetic to paramagnetic transition was sharp with Curie temperature TC=737 K, which further confirmed that the samples were single phase. However, it was found that the coercivity, saturation magnetization and the squareness ratio of the synthesized SrFe12O19 samples were lower than the theoretical values, which could be explained by the multi-domain structure and the increase of the demagnetizing factor.
We report the concept of a near-field memory device based on the radiative bistability effect in the system of two closely separated parallel plates of SiO2 and VO2 which exchange heat by thermal ...radiation in vacuum. We demonstrate that the VO2 plate, having metal-insulator transition at 340 K, has two thermodynamical steady-states. One can switch between the states using an external laser impulse. We show that due to near-field photon tunneling between the plates, the switching time is found to be only 5 ms which is several orders lower than in case of far field.
New results from DAMA/LIBRA Bernabei, R.; Belli, P.; Cappella, F. ...
The European physical journal. C, Particles and fields,
05/2010, Letnik:
67, Številka:
1-2
Journal Article
Recenzirano
Odprti dostop
DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N. Here the results obtained with a further exposure of 0.34 ton × yr are presented. They refer to two further annual cycles ...collected one before and one after the first DAMA/LIBRA upgrade occurred on September/October 2008. The cumulative exposure with those previously released by the former DAMA/NaI and by DAMA/LIBRA is now 1.17 ton × yr, corresponding to 13 annual cycles. The data further confirm the previous positive results obtained investigating the presence of Dark Matter (DM) particles in the galactic halo by means of the model independent Dark Matter annual modulation signature; the confidence level is now 8.9
σ
for the cumulative exposure. In particular, with the cumulative exposure the modulation amplitude of the
single-hit
events in the (2–6) keV energy interval measured in NaI(Tl) target is (0.0116±0.0013) cpd/kg/keV; the measured phase is (146±7) days and the measured period is (0.999±0.002) yr, values well in agreement with those expected for the DM particles.
•BaTiO3–CoFe2O4 multilayer films were prepared by chemical solution deposition.•The strain is relaxed and the grain size is increased with the films thickness.•Permittivity and saturation ...polarization increase with the films thickness.•A decrease in saturation magnetization of the thickest film is observed.•The effect of the microcracks on the films properties is also investigated.
BaTiO3–CoFe2O4 multilayer thin films with different thickness were fabricated by chemical solution deposition. The thickness effect on the multilayer films properties was investigated. As a result, the strain in the films is relaxed and the mean grain size is increased with increasing films thickness. Some microcracks are generated due to the large thermal expansion coefficient misfit and exert a significant impact on the films properties. Dielectric constant and saturation polarization increase with the films thickness. A decrease in saturation magnetization of the thickest film is observed and attributed to the pinning effect of the microcracks to the domain wall movement. The variation of magnetodielectric effect is analyzed and attributed to the combined effect of the magnetoresistance effect and Maxwell–Wagner effect. Finally, the results indicate that the optimal thickness of the BTO–CFO multilayer films via CSD method is about 500nm.
Context.
Kink oscillations in coronal loops are ubiquitous, and we apply the observed parameters of oscillations to estimate the magnetic field strength of the loops.
Aims.
In this work, we report ...our multiwavelength observations of the transverse oscillation of a large-scale coronal loop with a length of ≥350 Mm. The oscillation was induced by a blowout coronal jet, which was related to a C4.2 circular-ribbon flare (CRF) in active region 12434 on 2015 October 16. We aim to determine the physical parameters in the coronal loop, including the Alfvén speed and the magnetic field strength.
Methods.
The jet-induced kink oscillation was observed in extreme ultraviolet (EUV) wavelengths by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Line-of-sight magnetograms were observed by the Helioseismic and Magnetic Imager (HMI) on board the SDO. We took several slices along the loop to assemble time-distance diagrams and used an exponentially decaying sine function to fit the decaying oscillation. The initial amplitude, period, and damping time of kink oscillations were obtained. Coronal seismology of the kink mode was applied to estimate the Alfvén speed and the magnetic field strength in the oscillating loop. In addition, we measured the magnetic field of the loop through nonlinear force-free field (NLFFF) modeling using the flux rope insertion method.
Results.
The oscillation is most pronounced in AIA 171 and 131 Å. The oscillation is almost in phase along the loop with a peak initial amplitude of ∼13.6 Mm, meaning that the oscillation belongs to the fast standing kink mode. The oscillation lasts for ∼3.5cycles with an average period of ∼462 s and an average damping time of ∼976 s. The values of
τ
/
P
lie in the range of 1.5–2.5. Based on coronal seismology, the Alfvén speed in the oscillating loop is estimated to be ∼1210 km s
−1
. Two independent methods are applied to calculate the magnetic field strength of the loop, resulting in 30–43 G using coronal seismology and 21–23 G using NLFFF modeling.
Conclusions.
The magnetic field strength estimated using two different approaches are on the same order of magnitude, which confirms the reliability of coronal seismology by comparing with NLFFF modeling.
Background. Malnourished children are at increased risk for death due to diarrhea. Our goal was to determine the contribution of specific enteric infections to malnutrition-associated diarrhea and to ...determine the role of enteric infections in the development of malnutrition. Methods. Children from an urban slum in Bangladesh were followed for the first year of life by every-other-day home visits. Enteropathogens were identified in diarrheal and monthly surveillance stools; intestinal barrier function was measured by serum endocab antibodies; and nutritional status was measured by anthropometry. Results. Diarrhea occurred 4.69 ± 0.19 times per child per year, with the most common infections caused by enteric protozoa (amebiasis, cryptosporidiosis, and giardiasis), rotavirus, astrovirus, and enterotoxigenic Escherichia coli (ETEC). Malnutrition was present in 16.3% of children at birth and 42.4% at 12 months of age. Children malnourished at birth had increased Entamoeba histolytica, Cryptosporidium, and ETEC infections and more severe diarrhea. Children who became malnourished by 12 months of age were more likely to have prolonged diarrhea, intestinal barrier dysfunction, a mother without education, and low family expenditure. Conclusions. Prospective observation of infants in an urban slum demonstrated that diarrheal diseases were associated with the development of malnutrition that was in turn linked to intestinal barrier disruption and that diarrhea was more severe in already malnourished children. The enteric protozoa were unexpectedly important causes of diarrhea in this setting. This study demonstrates the complex interrelationship of malnutrition and diarrhea in infants in low-income settings and points to the potential for infectious disease interventions in the prevention and treatment of malnutrition.
A linear Fresnel reflector (LFR) solar collector with modified V-shaped cavity receiver was investigated both experimentally and theoretically in this paper. Simplified ray tracing technique was ...employed to optimize the optical design of the LFR system. The Monte Carlo ray tracing method was used to predict the optical performance of the proposed LFR system. A 2D mathematical model was developed to investigate the effect of receiver surface temperature on the overall heat transfer coefficient which reflects the thermal performance of the modified linear cavity receiver. CFD simulation was carried out for the modified cavity receiver treated at various surface temperatures within a range of 90–150 °C, by taking into account the conductive, convective and radiative heat losses. Experimental results show that the overall heat loss coefficient varied from 6.25 to 7.52 W/m2 K for the tested surface temperature range, with an average deviation of about 12% when compared with simulation results. Also, at higher surface temperatures, heat loss through radiative mode was predominant and the system stagnation was found to be about 260 °C with optimal operating temperature of about 121 °C. The thermal efficiency decreased from 45% to 37% as the average surface temperature increased from 90 °C to 150 °C.
► An LFR solar collector was investigated both experimentally and theoretically. ► Simplified ray tracing technique was used to optimize the optical design. ► The MCRT method was used to predict the optical performance of the LFR system. ► Thermal performance of the LFR system was evaluated by CFD method and experiments. ► The LFR system is a promising technology in generating mid-temperature heat.
Angiogenesis is a key step in tumor growth and metastasis. The mechanism by which osteopontin (OPN) induces the angiogenesis of endothelial cells remains unclear. Here, we show that OPN confers ...cytoprotection through the activation of the PI3K/Akt pathway with subsequent upregulation of Bcl-xL and activation of nuclear factor-kappaB. OPN enhances the expression of vascular endothelial growth factor (VEGF) through the phosphorylation of AKT and extracellular signal-regulated kinase (ERK). In turn, OPN-induced VEGF activates PI3K/AKT and the ERK1/2 pathway as a positive feedback signal. Blocking the feedback signal by anti-VEGF antibody, PI3-kinase inhibitor or ERK inhibitor can partially inhibit the OPN-induced human umbilical vein endothelial cell (HUVEC) motility, proliferation and tube formation, while blocking the signal by anti-OPN or anti-alphavbeta3 antibody completely abrogates the biological effects of OPN on HUVECs. In addition, blood vessel formation is also investigated in vivo. The antiangiogenesis efficacy of anti-OPN antibody in vivo is more effective than that of anti-VEGF antibody, which only blocks the feedback signals. These data show that OPN enhances angiogenesis directly through PI3K/AKT- and ERK-mediated pathways with VEGF acting as a positive feedback signal. The results suggest that OPN might be a valuable target for developing novel antiangiogenesis therapy for treatment of cancer.
We experimentally demonstrate a large area, optically opaque plasmonic absorber which can absorb 95% of visible light with an effective thickness of less than 150 nm. The absorber comprises, from top ...to bottom, a mono-layer of random gold nanoparticles, a dielectric spacer, and a bottom gold reflector. Reflectometry analyses show that its absorption is insensitive to the incidence's polarization or angle when the incident angle is less than 50°. At a larger incident angle, reflection increases and absorption spectra differ for two polarizations. Numerical simulations based on a 3D finite-element method suggest that the high absorbance is due to collective efforts of dipolar particle resonances, most often strongly coupled and forming chain resonances, as well as coupling of light to the surface plasmon polariton, irrespective of the incidence's polarization, through the top-layer particles. Similar high absorptivity is also demonstrated with silver or aluminum as the bottom reflector. These highly efficient visible light absorbers can be potential candidates for a range of passive and active photonic applications, including solar-energy harvesting as well as producing artificial colors on a large scale.
The aerodynamic loads for MW scale horizontal-axis wind turbines are calculated and analyzed in the established coordinate systems which are used to describe the wind turbine. In this paper, the ...blade element momentum (BEM) theory is employed and some corrections, such as Prandtl and Buhl models, are carried out. Based on the B-L semi-empirical dynamic stall (DS) model, a new modified DS model for NACA63-4xx airfoil is adopted. Then, by combing BEM modified theory with DS model, a set of calculation method of aerodynamic loads for large scale wind turbines is proposed, in which some influence factors such as wind shear, tower, tower and blade vibration are considered. The research results show that the presented dynamic stall model is good enough for engineering purpose; the aerodynamic loads are influenced by many factors such as tower shadow, wind shear, dynamic stall, tower and blade vibration, etc, with different degree; the single blade endures periodical changing loads but the variations of the rotor shaft power caused by the total aerodynamic torque in edgewise direction are very small. The presented study approach of aerodynamic loads calculation and analysis is of the university, and helpful for thorough research of loads reduction on large scale wind turbines.
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