Cyclic operation of porous combustor-heater (PCH)

A porous combustor-heater (PCH) with cyclic flow reversal combustion (CFRC) was investigated on the basis of simulation for practical applications. Emphasis was placed on determination of the optimal switching period under which the system will offer a high thermal efficiency with low emissions. It was shown that by using the CFRC thermal performance, emissions are strongly affected by the switching period through the interaction of the hot zone movement within the reactor and by heat transfer to the tube bank. An optimal switching period of about 120-180 s was found with maximum thermal efficiency to be as high as 85% with low emissions of CO and NO_x of 200 and 20 ppm, respectively. The CFRC system yields higher thermal efficiency with higher combustion efficiencies than the unidirectional steady state regime at the same experimental conditions.     

Isolation of quinone reductase (QR) inducing agents from ginger rhizome and their in vitro anti-inflammatory activity

To investigate the potential activity of ginger rhizome extracts to induce quinone reductase (QR), we performed bioactivity-guided fractionation using a murine hepatoma cell (Hepa 1c1c7) bioassay. Anti-inflammatory effects were then studied utilizing lipopolysaccharide (LPS)-stimulated mouse macrophage (RAW 264.7) cells. An ethyl acetate-partitioned fraction from ethanolic extract, rich in both QR inducing potency and anti-inflammatory activity, was subjected to repeated silica gel column and preparative thin layer chromatography to yield three compounds. The three isolated compounds were [6]-shogaol, 1-dehydro-[6]-gingerdione and hexahydrocurcumin. [6]-Dehydroshogaol, a minor component in ginger rhizome, was chemically synthesized and used for comparison in the subsequent bioassay based on its excellent QR inducing potency. Results showed that [6]-dehydroshogaol had the highest ability to induce QR activity (CD = 9.23 ± 0.22 ??M), followed by 1-dehydro-[6]-gingerdione (CD = 13.24 ± 0.45 ??M), and then hexahydrocurcumin (CD = 68.81 ± 3.90 ??M). Increasing QR activity in induced cells was associated with elevated expression of NQO-1 protein as confirmed by Western blot. [6]-Dehydroshogaol, [6]-shogaol and 1-dehydro-[6]-gingerdione were also potent inhibitors of nitric oxide (NO) synthesis in activated macrophages. Their IC₅₀ values ranged from 5.80 ± 1.27 to 25.06 ± 4.86 ??M. Hexahydrocurcumin exhibited the weakest inhibitory effect (IC₅₀ = 304.76 ± 54.80 ??M). These findings contribute to our theoretical understanding of the potential beneficial effects of consuming ginger as food and/or dietary supplement.     

Surface charge heterogeneities measured by atomic force microscopy

Unfavorable aggregation and deposition of colloidal particles in natural and engineered systems is still a subject of debate. Complicating factors such as surface roughness, secondary minimum aggregation, and the nature of discrete surface charge and surface potential make it difficult to attribute a specific cause to these phenomena. The presence of surface charge heterogeneity and its influence on interaction forces, which are responsible for aggregation and deposition, are studied in this work through the application of atomic force microscopy (AFM). Force-volume-mode AFM was used to map interaction forces on a surface and relate them to surface charge heterogeneities. The experimental system consisted of a silica plate and a standard silicon nitride AFM tip. Copper ions were used for sorption on the silica surface in order to modify the surface charge and cause charge reversal. Different concentrations of copper ions were selected to identify conditions of partial coverage of the silica surface. The pH and ionic strength of the solutions were varied, and the extension of the surface charge modification and its influence on the resulting interaction forces were monitored via AFM force measurements. Depending on the pH and ionic strength, the interaction force was found to change at certain regions on the surface from attraction to either weak or strong repulsion. Force imaging allowed the visual localization of zones of strong repulsive interaction that diminished in size with increasing ionic strength. X-ray photoelectron spectroscopy analysis was used to confirm the presence of copper on the surface. Local charge differences on a surface result in local differences in surface forces, not only in magnitude but also in direction. This behavior may explain the aggregation, deposition, and transport of colloidal particles under unfavorable chemical conditions.     

Isolation and synergism of in vitro anti-inflammatory and quinone reductase (QR) inducing agents from the fruits of Morinda citrifolia (noni)

The tropical fruits and fruit products of Morinda citrifolia, commonly known as noni, are consumed as a food or dietary supplement with purported health benefits. The objective of this study was to investigate the potential anti-inflammatory and cancer preventive effects of noni fruit puree extracts. Bioassay-guided fractionation of an ethyl acetate (EtOAc) extract of noni, comprising ~ 2% noni puree solids, led to the isolation of scopoletin (1), rutin (2), and quercetin (3). Quantitative HPLC analysis of the EtOAc extract revealed levels (dry weight basis) of scopoletin at 0.62 ??mol/g, quercetin at 0.26 ??mol/g and rutin at 0.045 ??mol/g. Scopoletin and quercetin inhibited the production of nitric oxide (NO) in a concentration-dependent manner in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells and exhibited quinone reductase (QR) induction in cultured Hepa 1c1c7 cells. Increases in QR activity in induced cells were associated with increases in QR protein as confirmed by Western blots. Combinations of scopoletin and quercetin at a low (< 10 ??M) concentration resulted in synergistic suppression in nitric oxide (NO) production and down-regulated inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 expressions in LPS-induced RAW 264.7 macrophage cells. These results suggest that the combinations of noni compounds with different groups of chemical structures might be useful to efficiently suppress inflammatory and carcinogenic processes related to iNOS and COX-2 gene overexpression. These findings may provide some basis for the purported in vitro anti-inflammatory and anti-cancer effects of noni fruits as functional foods and dietary supplements.     

In vitro antioxidant and anti-inflammatory activities of 1-dehydro-[6]-gingerdione, 6-shogaol, 6-dehydroshogaol and hexahydrocurcumin

Hexahydrocurcumin, 1-dehydro-[6]-gingerdione, 6-dehydroshogaol and 6-shogaol were evaluated for their antioxidant and anti-inflammatory activities in the present study. The relative antioxidant potencies of ginger compounds decreased in similar order of 1-dehydro-[6]-gingerdione, hexahydrocurcumin>6-shogaol>6-dehydroshogaol in both 1,1-diphenyl-2-picyrlhydrazyl (DPPH) radical-scavenging and trolox equivalent antioxidant capacity (TEAC) assays. All tested compounds could attenuate lipopolysaccharide (LPS)-elicited increase of prostaglandin E2 (PGE(2)) in murine macrophages (RAW 264.7) in a concentration-dependent manner but hexahydrocurcumin of 7μM and 6-shogaol of 7μM. The strongest inhibitory effect was observed for 6-dehydroshogaol and 6-shogaol at 14μM with the inhibition of 53.3% and 48.9%, respectively. Furthermore, both 6-dehydroshogaol and 1-dehydro-[6]-gingerdione significantly suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins in a concentration-dependent fashion. These results contribute to our theoretical understanding of the potential beneficial effects of consuming ginger as a food and/or dietary supplement.     

Low-harmonic GTO converter for fundamental power factorcompensation

A low-harmonic GTO (gate turn-off) thyristor AC-to-DC converter with line current lead-lag phase shift control ability is proposed and analyzed. The converter can be used either as a low-harmonic GTO-controlled rectifier or a fundamental input power factor compensator in a power supply system. The effect of PWM (pulse width modulation) current phase number on the harmonic contents and converter output voltage control range is investigated. Lower order input current harmonics are eliminated over a wide range, using a specially designed PWM current pattern. The effect of the PWM current pulse number on the power factor compensation characteristic is investigated