Obesity is one of the major health problems throughout the world. The present study investigated the preventive effect of epilactose – a rare non-digestible disaccharide – on obesity and metabolic disorders in mice fed high-fat (HF) diets. Feeding with HF diets increased body weight gain, fat pad weight and adipocyte size in mice (P<0·01), and these increases were effectively prevented by the use of supplemental epilactose without influencing food intake (P<0·01). Caecal pools of SCFA such as acetic and propionic acids in mice fed epilactose were higher compared with mice not receiving epilactose. Supplemental epilactose increased the expression of uncoupling protein (UCP)-1, which enhances energy expenditure, to 2-fold in the gastrocnemius muscle (P=0·04) and to 1·3-fold in the brown adipose tissue (P=0·02) in mice fed HF diets. Feeding HF diets induced pro-inflammatory macrophage infiltration into white adipose tissue, as indicated by the increased expression of monocyte chemotactic protein-1, TNF-α and F4/80, and these increases were attenuated by supplemental epilactose. In differentiated myogenic-like C2C12 cells, propionic acid, but not acetic or n-butyric acids, directly enhanced UCP-1 expression by approximately 2-fold (P<0·01). Taken together, these findings indicate that the epilactose-mediated increase in UCP-1 in the skeletal muscle and brown adipose tissue can enhance whole-body energy expenditure, leading to effective prevention of obesity and metabolic disorders in mice fed HF diets. It is suggested that propionic acid – a bacterial metabolite – acts as a mediator to induce UCP-1 expression in skeletal muscles.

Elevated postprandial hyperglycaemia and oxidative stress increase the risks of type 2 diabetes and CVD. Green tea catechin possesses antidiabetic properties and antioxidant capacity. In the present study, we examined the acute and continuous effects of ingestion of catechin-rich green tea on postprandial hyperglycaemia and oxidative stress in healthy postmenopausal women. Participants were randomly assigned into the placebo (P, n 11) or green tea (GT, n 11) group. The GT group consumed a catechin-rich green tea (catechins 615 mg/350 ml) beverage per d for 4 weeks. The P group consumed a placebo (catechins 92 mg/350 ml) beverage per d for 4 weeks. At baseline and after 4 weeks, participants of each group consumed their designated beverages with breakfast and consumed lunch 3 h after breakfast. Venous blood samples were collected in the fasted state (0 h) and at 2, 4 and 6 h after breakfast. Postprandial glucose concentrations were 3 % lower in the GT group than in the P group (three-factor ANOVA, group × time interaction, P< 0·05). Serum concentrations of the derivatives of reactive oxygen metabolites increased after meals (P< 0·05), but no effect of catechin-rich green tea intake was observed. Conversely, serum postprandial thioredoxin concentrations were 5 % higher in the GT group than in the P group (three-factor ANOVA, group × time interaction, P< 0·05). These findings indicate that an acute ingestion of catechin-rich green tea has beneficial effects on postprandial glucose and redox homeostasis in postmenopausal women.

We show that high-efficiency and low-degradation hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells can be obtained by depositing absorber layers in a triode-type plasma-enhanced chemical vapor deposition (PECVD) process. Although the deposition rate is relatively low (0.01-0.03 nm/s) compared to the conventional diode-type PECVD process (∼0.2 nm/s), the light-induced degradation in conversion efficiency of single-junction solar cell is substantially reduced (Δη/ηini∼10%) due to the suppression of light-induced metastable defects in the a-Si:H absorber layer. So far, we have attained an independently-confirmed stabilized efficiency of 10.11% for a 220-nm-thick a-Si:H solar cell which was light soaked under 1 sun illumination for 1000 hours at cell temperature of 50°C. We further demonstrate that stabilized efficiencies as high as 10% can be maintained even when the solar cell is thickened to >300 nm.

Periodically textured back reflectors with hexagonal dimple arrays are applied to thin-film microcrystalline silicon (μc-Si:H) solar cells for enhancing light trapping. The period and aspect ratio of the honeycomb textures have a big impact on the photovoltaic performance. When the textures have a moderate aspect ratio, the optimum period for obtaining a high short circuit current density (JSC) is found to be equal to or slightly larger than the cell thickness. If the cell thickness exceeds the texture period, the cell surface tends to be flattened and texture-induced defects are generated, which constrain the improvement in JSC. Based on these findings, we have fabricated optimized μc-Si:H cells achieving a high active-area efficiency exceeding 11% and a JSC of 30 mA/cm2.

This paper presents our material studies on hydrogenated microcrystalline silicon (μc-Si:H) and microcrystalline silicon-germanium alloy (μc-Si1-xGex:H) thin films for the development of high efficiency p-i-n junction solar cells. In μc-Si:H solar cells, we have evaluated the structural properties of the intrinsic μc-Si:H layers grown by plasma-enhanced chemical vapor deposition at high deposition rates (>2 nm/s). Several design criteria for the device grade μc-Si:H are proposed in terms of crystallographic orientation, grain size and grain boundary passivation. Meanwhile, in μc-Si1-xGex:H solar cells, we have succeeded in boosting the infrared response of solar cell upon Ge incorporation up to x∼0.2. Nevertheless, a degradation of solar cell parameters is observed for large Ge contents (x>0.2) and thick i-layers (> 1 μm), which is attributed to the influence of the Ge dangling bonds that act as acceptorlike states in undoped μc-Si1-xGex:H. To improve the device performance, we introduce an oxygen doping technique to compensate the native defect acceptors in μc-Si1-xGex:H p-i-n solar cells.

The characterization of void-related microstructure in amorphous and microcrystalline Ge:H films is reported. Various methods are applied including effusion measurements of hydrogen and of implanted helium and neon, measurements of the infrared absorption of C-H bonds due to in-diffusion of contaminants and of the stretching modes of bonded hydrogen. Several microstructure effects like interconnected voids and isolated voids and a quite different material homogeneity are detected and are found to depend on the preparation conditions. Amorphous Ge:H can be prepared with a (largely) homogeneous structure while microcrystalline Ge:H tends to consist of compact grains surrounded by more or less open voids. Enhanced substrate temperatures (Ts ≈ 250°C) favour the growth of more compact material.

This paper presents microcrystalline silicon (μ c-Si:H) p-i-n (superstrate-type) solar cells fabricated by 100 MHz plasma-enhanced chemical vapor deposition (PECVD) at i-layer deposition rates of >2 nm/s. Under high-rate conditions, in particular, the deposition pressure is found to play a dominant role in determining short circuit current (Jsc) of solar cell. With anincrease in deposition pressure from 3 to 7-9 Torr, Jsc increases by more than 50% due to a significant improvement in the long wavelength (>600 nm) responses, which essentially leads to high efficiency (∼8%) solar cells in the 2-3 nm/s deposition rate range. Further progress in solar cell efficiency has been made by the improvement of TCO/p and p/i interfaces. As a result, efficiency reaches 9.13% (Jsc=23.7 mA/cm2,Voc=0.528 V,FF=0.73) with a 2.3μm-thick i-layer grown at 2.3 nm/s. Transmission electron microscopy and secondary-ion mass spectroscopy studies reveal that samples prepared at lower pressure (∼4 Torr) comprise many grain boundaries due to disordered grain growth, which induces an anomalous incorporation of atmospheric impurities (predominantly oxygen) after exposing sample to air. In contrast, the high-pressure process (<7 Torr) provides denser grain columns coalesced with [110]-oriented crystallites, which in turn inhibits impurities from penetrating deeper in the film. Based on above results, we propose that the less post-oxidation behavior associated with the denser microstructure of high-pressure-grown μc-Si:H is responsible for the excellent charge collection in p-i-n solar cells.