STEROLS AND FLAVONE FROM THE LEAVES OF Vernonia amygdalina Del. GROWING IN THUA THIEN HUE

By using various chromatographic methods, two sterols and one flavone, vernoniamygda A (1), vernoniamygda B (2), and luteolin (3) were isolated from the methanol extract of the leaves of Vernonia amygdalina. Their structures were determined using 1D, 2D-NMR and ESI-MS analysis as well as by comparison with the reported data. Compounds 1 and 2 were reported from natural for the first time

Curie Temperature of Diluted Magnetic Semiconductors: the Influence of the Antiferromagnetic Exchange Interaction

The coherent potential approximation and mean field approximation are used to calculate the free energy of the coupled carrier – localized spin system in III-V diluted magnetic semiconductors. Thus the magnetic transition temperature Tc can be determined and its dependence on important model parameters. We show that the strong antiferromagnetic superexchange interaction between nearest neighbour sites considerably reduces the Curie temperature

Mott Transition of the Half-filled Hubbard Model in a Two-dimensional Frustrated Lattice

Using coherent potential approximation we study zero-temperature Mott transition of the half-filled Hubbard model in a two-dimensional square lattice with geometrical frustration. It turns out that the geometrical frustration reduces the gap between the Hubbard bands. As a result the metallic phase is stabilized up to a fairly large value of the on-site Coulomb interaction. We found that the critical value $U_C$ for the Mott transition is enhanced by the geometrical frustration. Our results are in good agreement with the ones obtained by the single-site dynamical mean-field theory

Mott Transitions in the 2-band Hubbard Model: A Coherent Potential Approximation Study

The half-filled isotropic degenerate two-band Hubbard model is studied within coherent potential approximation. The model is characterized by an Ising-type Hund’s exchange coupling, intra- and inter-orbital Coulomb parameters. We found that the band degeneracy slightly reduces the Mott-Hubbard critical value $U_C$. We reveal that the system can have two distinct critical values for Mott-Hubbard transitions

Effect of blue light on the photosynthesis and flavonoid accumulation in leaves of Hedyotis corymbosa (L.) Lam.

In plants, blue light with a short wavelength can promote light reaction in photosynthesis and increase dry mass. Photosynthesis plays an important role in supporting carbohydrates for primary and secondary metabolism processes. Flavonoids are phenolic compounds, a class of plant secondary metabolites, that can be obtained from many medicinal herbs. These phenolic compounds are involved in the reactive oxygen species scavenging system, inhibit lipid peroxidation by free-radical, chelate redox-active metals resulting in their antioxidant ability and cardioprotective effects. In this study, H. corymbosa (L.) Lam., one of the common medicinal herbs, was cultured for 4 weeks under conditions of 450 nm blue LED (light-emitting diode) lights at the different light intensity as treatments and fluorescent lamp light as a control to investigate the effects of blue light on photosynthesis and flavonoid accumulation in leaves. The results show that blue light at 450 nm promoted photosynthetic rate by enhancing stomatal opening, electron transport rate in light reaction. Blue light also enhanced photoprotection by decrease the quantum yield of non-photochemical losses, increase the quantum yield of non-photochemical quenching and gained 24% more in dry mass. The accumulation of flavonoid and total phenolic compounds in leaves was followed by a decrease in sucrose. These events proved that blue light enhances photosynthesis and increase carbohydrate and flavonoid accumulation in leaves

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ERRATU

Influence of internal curing on compressive strength and drying shrinkage of super-sulfated cement mortar

The current study aims at assessing the effect of using cold-bonded fly ash based artificial lightweight aggregate (ALWA) as an internal curing (IC) agent on the compressive strength and drying shrinkage of a typical super-sulfated cement (SSC) produced with a mixture of 85% slag, 10% gypsum, and minor amount of 5% blended Portland cement (PCB). The ALWA was used as partial replacement of fine aggregate (FA) at values of 25, 50, 75, and 100 vol.%. Experimental results showed that the ALWA partially replacing FA in range of 25–100 vol.% significantly decreased both the unit weight and dried density of the fresh and hardened IC-SSC mortars at average values of 13.9% and 20.0%, when compared with the reference SSC mortar, respectively. The ALWA increment continuously reduced the compressive strengths of the hardened IC-SSC mortars. But, at 28 days of curing, the hardened IC-SSC mortar containing the ALWA amount partially replacing FA up to 50 vol.% showed compressive strength reaching 89.3%, and comparable or slightly lower drying shrinkage in comparison with the reference SSC mortar without the IC agent