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Enterohepatic circulation of 12α-hydroxylated (12αOH) bile acid (BA) is enhanced depending on the energy intake in high-fat diet-fed rats. Such BA metabolism can be reproduced using a diet supplemented with cholic acid (CA), which also induces simple steatosis, without inflammation and fibrosis, accompanied by some other symptoms that are frequently observed in the condition of non-alcoholic fatty liver in rats. We investigated whether supplementation of the diet with raffinose (Raf) improves hepatic lipid accumulation induced by the CA-fed condition in rats. After acclimation to the AIN-93-based control diet, male Wistar rats were fed diets supplemented with a combination of Raf (30 g/kg diet) and/or CA (0·5 g/kg diet) for 4 weeks. Dietary Raf normalised hepatic TAG levels (two-way ANOVA P < 0·001 for CA, P = 0·02 for Raf and P = 0·004 for interaction) in the CA-supplemented diet-fed rats. Dietary Raf supplementation reduced hepatic 12αOH BA concentration (two-way ANOVA P < 0·001 for CA, P = 0·003 for Raf and P = 0·03 for interaction). The concentration of 12αOH BA was reduced in the aortic and portal plasma. Raf supplementation increased acetic acid concentration in the caecal contents (two-way ANOVA P = 0·001 as a main effect). Multiple regression analysis revealed that concentrations of aortic 12αOH BA and caecal acetic acid could serve as predictors of hepatic TAG concentration (R2 = 0·55, P < 0·001). However, Raf did not decrease the secondary 12αOH BA concentration in the caecal contents as well as the transaminase activity in the CA diet-fed rats. These results imply that dietary Raf normalises hepatic lipid accumulation via suppression of enterohepatic 12αOH BA circulation.
Intestinal bacteria are involved in bile acid (BA) deconjugation and/or dehydroxylation and are responsible for the production of secondary BA. However, an increase in the production of secondary BA modulates the intestinal microbiota due to the bactericidal effects and promotes cancer risk in the liver and colon. The ingestion of Bacillus coagulans improves constipation via the activation of bowel movement to promote defaecation in humans, which may alter BA metabolism in the intestinal contents. BA secretion is promoted with high-fat diet consumption, and the ratio of cholic acid (CA):chenodeoxycholic acid in primary BA increases with ageing. The dietary supplementation of CA mimics the BA environment in diet-induced obesity and ageing. We investigated whether B. coagulans lilac-01 and soya pulp influence both BA metabolism and the maintenance of host health in CA-supplemented diet-fed rats. In CA-fed rats, soya pulp significantly increased the production of secondary BA such as deoxycholic acid and ω-muricholic acids, and soya pulp ingestion alleviated problems related to plasma adiponectin and gut permeability in rats fed the CA diet. The combination of B. coagulans and soya pulp successfully suppressed the increased production of secondary BA in CA-fed rats compared with soya pulp itself, without impairing the beneficial effects of soya pulp ingestion. In conclusion, it is possible that a combination of prebiotics and probiotics can be used to avoid an unnecessary increase in the production of secondary BA in the large intestine without impairing the beneficial functions of prebiotics.
The reasons why the open circuit voltage (Voc) of high-x CuIn1-xGaxSe2 (CIGS)/ZnO solar cells remain low are discussed. Here it is shown that the Voc ceiling can be interpreted simply on the basis of a model that the valence-band energy (Ev) of CIGS is almost immovable irrespective of x. When the conduction-band energy (Ec) of ZnO is lower than that of high-x CIGS (DEc<0), the built-in potential (Vbi) of a CIGS/ZnO junction is equivalent to the flat-band potential (Vbi) that arises from the separation between the Fermi energies of the two materials. If the Ev (and therefore the Fermi energy) of p-type CIGS is constant with increasing x, the Vbi and Voc that follows the Vbi remain unchanged since the Fermi energy of ZnO is constant. This unchangeable Voc reduces the conversion efficiency of high-x CIGS cells in cooperation with reduced photocurrents due to a larger bandgap. A positive offset, ΔEc>o gives rise to a photoelectrons barrier in the conduction-band that partially cancels Voc, thus the Voc of a low-x CIGS cell is governed by the Ec of CIGS. Based upon this concept, a material selection guideline is given for the windows and transparent electrodes appropriate for high-x CIGS absorbers-based solar cells.
Using EBIC and EDX measurements, CIGS solar cells prepared under several different conditions were observed and characterized. The results of EBIC and EDX measurements suggest that Cd plays an important role in the forming of a buried pn-junction in the CIGS layer via diffusion, and de-emphasize the possibility of the formation of the hetero pn-junction at the CdS/CIGS heterointerface. The correlation of the extent of the space charge region and the observed shift in the pn-junction location with the diffusion of the constituent elements in CIGS was investigated.
We have fabricated CIGS:Fe polycrystalline thin films using a standard three-stage method, and investigated the effects of Fe doping on cell performances. The Ga / (In+Ga) ratio was varied between 0.3 ˜ 1.0 (= CGS), and the Fe concentration was varied between 0.0 ˜ 1.2 mol%. The films were characterized by various means, including the cell performance. Increment of the grain size with higher Fe content was observed. Redshift with higher Fe content was observed in the absorbance spectra. The spectral response of the fabricated solar cells deteriorated with higher Fe content, from the long wavelength side.
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