Jiang-Miao Hu

Study of nonlinear processes of a large experimental thermoacoustic-Stirling heat engine by using computational fluid dynamics

This article focuses on using computational fluid dynamics (CFD) method to study several important nonlinear phenomenon and processes of a large experimental thermoacoustic-Stirling heat engine. First, the simulated physical model was introduced, and the suitable numerical scheme and algorithm for the time-dependent compressible thermoacoustic system was determined through extensive numerical tests. Then, the simulation results of the entire evolution process of self-excited thermoacoustic oscillation and the acoustical characteristics of pressure and velocity waves were presented and analyzed. Especially, the onset temperature and the saturation process of dynamic pressure were captured by the CFD simulation. In addition, another important nonlinear phenomenon accompanying the acoustic wave, which is the steady mass flow through the traveling-wave loop inside the thermoacoustic engine, was studied. To suppress the steady mass flow numerically, a fan model was adopted in the simulation. Finally, the multi...

Iridoids and Sesquiterpenoids from the Roots of Valeriana officinalis

Two new iridoids, volvaltrates A and B (1 and 2), and three new sesquiterpenoids, E-(-)-3beta,4beta-epoxyvalerenal (3), E-(-)-3beta,4beta-epoxyvalerenyl acetate (4), and mononorvalerenone (5), together with five known iridoids and two known sesquiterpenoids were isolated from the roots of Valeriana officinalis. The structures and relative configurations of 1-5 were elucidated by spectroscopic evidence. Compound 1 was an unusual iridoid with an oxygen bridge connecting C-3 and C-10, forming a cage-like structure, and compound 5 was a mononorsesquiterpenoid.

Five New Compounds from Dendrobium longicornu

A novel bibenzyl, a new bibenzyl, two new phenanthrenes, and a new lignin glycoside, namely longicornuol A (1), 4-[2-(3-hdroxyphenol)-1-methoxyethyl]-2,6-dimethoxyphenol (2), 5-hydroxy-7-methoxy-9,10-dihydrophenanthrene-1,4-dione (3), 7-methoxy-9,10-dihydrophenanthrene-2,4,5-triol (4) and erythro-1-(4-O-beta-D-glucopyranosyl-3-methoxyphenyl)-2-[4-(3-hydroxypropyl)-2,6-dimethoxyphenoxy]-1,3-propanediol ( 5), together with 14 known compounds, were isolated from the stems of Dendrobium longicornu. All structures were elucidated by spectroscopic methods (NMR, MS, UV and IR). Anti-platelet aggregation activities of compounds 1 - 5 were also tested.

Two novel bibenzyls from Dendrobium trigonopus

Two novel bibenzyl trigonopols A (1) and B (2), together with seven known compounds, gigantol (3), tristin (4), moscatin (5), hircinol (6), naringenin (7), 3-(4-hydroxy-3-methoxyphenyl)-2-propen-1-ol (8), and ( − )-syringaresinol (9), have been isolated from the stems of Dendrobium trigonopus, of which compounds 6, 8, and 9 were isolated for the first time from this species. The structures of two new compounds were elucidated as threo-22-(17-hydroxyl-9-(3-hydroxyl-4-methoxy-phenethyl)-13,16,18-trimethoxy-21H-benzo[c]chromen-21-yl)ethane-22, 23-diol (1) and 9-(4-hydroxyl-3-methoxy-phenethyl)-17-(21-hydroxyl-20-methoxy-phenyl)chroman-11, 16-diol (2) on the basis of spectroscopic methods. Trigonopol A was found to exhibit antiplatelet aggregation activity in vitro with 67.55% inhibitory ration at 1.4337 × 10− 3 M.

Heat-driven thermoacoustic cryocooler operating at liquid hydrogen temperature with a unique coupler

A heat-driven thermoacoustic cryocooler is constructed. A unique coupler composed of a tube, reservoir, and elastic diaphragm is introduced to couple a traveling-wave thermoacoustic engine (TE) and two-stage pulse tube refrigerator (PTR). The amplitude of the pressure wave generated in the engine is first amplified in the coupler and the wave then passes into the refrigerator to pump heat. The TE uses nitrogen as its working gas and the PTR still uses helium as its working gas. With this coupler, the efficiency of the system is doubled. The engine and coupler match at a much lower operating frequency, which is of great benefit for the PTR to obtain a lower cooling temperature. The coupling place between the coupler and engine is also optimized. The onset problem is effectively solved. With these improvements, the heat-driven thermoacoustic cryocooler reaches a lowest temperature of 18.1K, which is the demonstration of heat-driven thermoacoustic refrigeration technology used for cooling at liquid hydrogen ...

Volvalerelactones A and B, Two New Sesquiterpenoid Lactones with an Unprecedented Skeleton from Valeriana officinalis var. latifolia

Volvalerelactones A and B (1 and 2), two new sesquiterpenoid lactones with an unprecedented 3/7/6 tricyclic ring system, were isolated from the roots of Valeriana officinalis var. latifolia. Their structures and relative configurations were elucidated by spectroscopic data and single-crystal X-ray diffraction crystallography, and the absolute configuration was assigned by computational methods. The possible biosynthetic pathways of 1 and 2 were also proposed.

Sesquiterpenoids and Lignans from the Roots of Valeriana officinalis L.

Two new guaiane‐type sesquiterpenoids, valerol A (1) and kessyl 3‐acetate (2), together with nine known compounds, valeracetate (3), anismol A (4), orientalol C (5), spatulenol (6), 4α,10α‐epoxyaromadendrane (7), (+)‐8‐hydroxypinoresinol (8), pinorespiol (9), pinoresinol 4‐O‐β‐D‐glucopyranoside (10), and 8‐hydroxypinoresinol 4′‐O‐β‐D‐glucopyranoside (11) were isolated from the roots of Valeriana officinalis. The structures and relative configurations of 1 and 2 were elucidated on the basis of spectroscopic methods (1D‐ and 2D‐NMR, MS, UV, and IR). These compounds were evaluated for inhibitory activity on acetylcholinesterase (AChE) and enhancing activity on nerve growth factor (NGF)‐mediated neurite outgrowth in PC12 cells.

Five new phenolic compounds from Dendrobium aphyllum.

One new phenanthrene, aphyllone A (1) and four new bibenzyl derivatives, aphyllone B (2) and aphyllals C-D (3-5), together with nine known compounds (6-14), were isolated from the stems of Dendrobium aphyllum (Roxb.) C. E. Fischer. The structures of these new compounds were elucidated by means of extensive spectroscopic analyses, and the absolute configuration of compound 1 was determined by single crystal X-ray diffraction and quantum calculations. Compounds 6, 8 and 14 inhibited NO production at the concentration of 25 μM in LPS-stimulated RAW264.7 cells with the inhibition (%) of 32.48, 35.68, and 38.50. Compound 2 possessed significant DPPH radical scavenging activity with scavenging percentage of 87.97% at the concentration of 100 μg/mL.

Iridoids and sesquiterpenoids from the roots of Valeriana jatamansi Jones

Three new iridoids, jatamanvaltrates R-S (1-2) and jatamanin Q (3), as well as three new sesquiterpenoids, valeriananoids D-E (4, 5) and clovane-2β-isovaleroxy-9α-ol (6), together with nine known compounds were isolated from the roots of Valeriana jatamansi Jones. Compound 2 was the first reported iridoid with fatty acid esters in the Valerianaceae family. The structures of new compounds were established on the basis of extensive spectroscopic analysis. Moreover, all the isolates were evaluated for inhibitory activity on acetylcholinesterase (AChE).

Cycloartane triterpenoid saponins from water soluble of Passiflora edulis Sims and their antidepressant-like effects.

ETHNOPHARMACOLOGICAL RELEVANCE Various species of genus Passiflora have been used as traditional folk medicines owing to their sedative and anti-hypertensive properties. Passiflora edulis Sims most widely grown in the warm temperate for their fragrant fruits and their twigs and leaves are used as a folk medicine for treating both anxiety and nervousness in American countries. The present study was to evaluate the antidepressant-like effect and the active components of this plant. MATERIALS AND METHODS The alcohol extracts of the stems (PES, 10 and 2 g/kg of the plant materials) and leaves (PEL, 10 and 2 g/kg of the plant materials) of Passiflora edulis Sims were orally administered to mice for 7 day. The animals were tested in the forced swim test (FST) and tail suspension test (TST). After behavioral assay of ethanol extract, phytochemical research of the stems and leaves (5.7 kg) of Passiflora edulis Sims were developed and further bioactive verification of monomeric compounds were conducted. RESULTS There are mainly cycloartane triterpenoids and their saponins isolated from this plant, including two new cycloartane triterpenoid saponins named cyclopassifloside ХII (1) and ХIII (2), together with six known cycloartane triterpenoids, cyclopassifloic acids B and E, cyclopassiflosides II, VI, IX and XI. The ethanol extract of Passiflora edulis Sims together with isolated compounds cyclopassiflosides IX and XI may possess antidepressant-like effect. CONCLUSIONS Cycloartane triterpenoid was one of the main compositions of Passiflora edulis Sims and possess antidepressant-like activity.