A quasi-3D hyperbolic shear deformation theory for functionally graded plates

A quasi-3D hyperbolic shear deformation theory for functionally graded plates is developed. The theory accounts for both shear deformation and thickness-stretching effects by a hyperbolic variation of all displacements across the thickness, and satisfies the stress-free boundary conditions on the top and bottom surfaces of the plate without requiring any shear correction factor. The benefit of the present theory is that it contains a smaller number of unknowns and governing equations than the existing quasi-3D theories, but its solutions compare well with 3D and quasi-3D solutions. Equations of motion are derived from the Hamilton principle. Analytical solutions for bending and free vibration problems are obtained for simply supported plates. Numerical examples are presented to verify the accuracy of the present theory

SOLUTIONS OF TEACHING AND LEARNING PHYSICAL EDUCATION AT HO CHI MINH CITY COLLEGE OF ECONOMICS, VIETNAM

Physical education is one of the compulsory courses at Ho Chi Minh City College of Economics. However, students have been observed to be less engaged in physical activities. Therefore, this study aims to investigate the solutions of teaching and learning physical education at this institution. In particular, fifteen solutions are proposed to enhance the quality of teaching and learning physical education.  Article visualizations

Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory

Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory is presented. The core of sandwich beam is fully metal or ceramic and skins are composed of a functionally graded material across the depth. Governing equations of motion and boundary conditions are derived from the Hamilton’s principle. Effects of power-law index, span-to-height ratio, core thickness and boundary conditions on the natural frequencies, critical buckling loads and load–frequency curves of sandwich beams are discussed. Numerical results show that the above-mentioned effects play very important role on the vibration and buckling analysis of functionally graded sandwich beams

TERPENOIDS FROM THE LEAVES AND STEMS OF DYSOXYLUM TPONGENSE

Study on chemical constituents from the leaves and stems of Dysoxylum tpongense Pierre resulted in the isolation of six known compounds (1–6). The chemical structures of isolated compounds were identified as cabraleahydroxylactone (1), cabraleahydroxylactone-3-acetate (2), (+) spathulenol (3), b-sitosterol (4), stigmasterol (5), and stigmast-4-en-3-one (6) by comparison of the physicochemical, interpretation of NMR and mass spectral data with that reported in the literature

Megastigmans and other compounds from Antidesma hainanensis Merr.

Four megastigmans 7-megastigmene-3-ol-9-one 3-O-[α-L-arabinofuranosyl-(1→6)-β-D-glucopyranoside]  (1),  alangionoside L (2),  alangioside (3), ampelopsisionoside (4), and other constituents as N–trans-feruloyloctopamide (5), trans-linalool-3,6-oxide-β-D-glucopyranoside (6),  5α,8α-dipioxiergosta-6,22-diene-3β-ol (7), and (Z)-2-hexenyl β-D-glucopyranoside (8) were isolated from the methanol extract of the Antidesma hainanensis leaves. Their chemical structures were successfully determined using NMR and ESI-MS analysis as well as in comparison with the reported data. This is the first report of these compounds from Euphorbiaceae family

A quasi-3D theory for vibration and buckling of functionally graded sandwich beams

This paper presents a finite element model for free vibration and buckling analyses of functionally graded (FG) sandwich beams by using a quasi-3D theory in which both shear deformation and thickness stretching effects are included. Sandwich beams with FG skins-homogeneous core and homogeneous skins-FG core are considered. By using the Hamilton’s principle, governing equations of motion for coupled axial–shear–flexural–stretching response are derived. The resulting coupling is referred to as fourfold coupled vibration and buckling. Numerical examples are carried out to investigate the thickness stretching effect on natural frequencies and critical buckling loads as well as mode shapes of sandwich beams for various power-law indexes, skin–core–skin thickness ratios and boundary conditions

Furanosesterterpenes from the marine sponge Ircinia echinata (Keller, 1889)

Four furanosesterterpene, (7E,12E,20Z,18β)-variabilin (1), (12E,20Z,18β)-8-hydroxyvariabilin (2), (7E,11E,3β)-3,7,11-trimethyl-14-(furan-3-yl)tetradec-7,11-dienoic acid (3), and furoscalarol (4), and one sterol, 3β-hydroxycholest-5-en-7-one (5) were isolated from the methanol extract of the sponge Ircinia echinata (Keller, 1889). Their structures were elucidated by 1D and 2D-NMR spectra and in comparison with those reported in the literature. Keywords. Sponge, Ircinia echinata, furanosesterterpene, sterol

Merosesquiterpenes from marine sponge Smenospongia cerebriformis

Using various chromatography methods, three merosesquiterpenes belonging to sesquiterpene quinone type, neodactyloquinone (1), dactyloquinone D (2), and dactyloquinone C (3) together with two indole derivatives indole-3-aldehyde (4) and indole-3-cacboxylic methyl ester (5) were isolated from the methanol extract of the Vietnamese marine sponge Smenospongia cerebriformis. Their structures were determined by 1D-, 2D-NMR spectra, HR-ESI-MS and in comparison with those reported in the literature. Keywords. Smenospongia cerebriformis, merosesquiterpene, sesquiterpene quinone, indole derivative

Biflavones and megastigmane glycosides from the leaves of Antidesma bunius.

Two biflavones, podocarpusflavone A (1) and amentoflavone (2) and two megastigmane glycosides, byzantionoside B (3) and (6S,9R)-roseoside (4) were isolated from the methanol extract of the leaves of Antidesma bunius. Their structures were determined by spectroscopic methods and in comparison with the published data. Keywords. Antidesma bunius, Euphorbiaceae, biflavone, megastigmane

Iridoid glycosides from Morinda tomentosa and their endoplasmic reticulum stress modulation activity

Three iridoids 1 - 3, asperulosidic acid, daphylloside, and asperuloside, were isolated from the methanol extract of the leaves of Morinda tomentosa. Their chemical structures were elucidated by 1D- and 2D-NMR spectra and in comparison with those reported in the literature. The effects of these compounds on the endoplasmic reticulum stress in XBP1-eGFP-transfected the 293 T cells were measured. Compound 3 significantly reduced the ER-stress both in DMSO-treated and thapsigargin-treated cells. Unlike this compound, compound 3 selectively reduced thapsigargin-induced ER-stress without any effect on the level of XBP1 splicing in DMSO-treated cells. These results suggested that compounds 2 and 3 can be suggested as new ER stress regulators