Ming-Chien Chyu

Two-phase pressure drop of refrigerants during flow boiling in small channels: an experimental investigation and correlation development ☆

Two-phase flow pressure drop measurements were made during a phase-change heat transfer process with three refrigerants (R-134a, R-12, and R-113) at six different pressures ranging from 138 kPa to 856 kPa, and in two sizes of round tubes (2.46 mm and 2.92 mm inside diameters) and one rectangular channel (4.06 x 1.7 mm). State-of-the-art large-tube correlations failed to satisfactorily predict the experimental data. The data were used to develop a new correlation for two-phase pressure drop during flow boiling in small channels. The correlation was then tested against the experimental data for the three refrigerants; the error was {+-}20%.

Group and home-based tai chi in elderly subjects with knee osteoarthritis: a randomized controlled trial

Objective: To evaluate the effects of tai chi consisting of group and home-based sessions in elderly subjects with knee osteoarthritis. Design: A randomized, controlled, single-blinded 12-week trial with stratification by age and sex, and six weeks of follow-up. Setting: General community. Participants: Forty-one adults (709 / 9.2 years) with knee osteoarthritis. Interventions: The tai chi programme featured six weeks of group tai chi sessions, 40 min/session, three times a week, followed by another six weeks (weeks 7 -12) of home-based tai chi training. Subjects were requested to discontinue tai chi training during a six-week follow-up detraining period (weeks 13-18). Subjects in the attention control group attended six weeks of health lectures following the same schedule as the group-based tai chi intervention (weeks 0 -6), followed by 12 weeks of no activity (weeks 7-18). Main outcome measures: Knee pain measured by visual analogue scale, knee range of motion and physical function measured by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were recorded at baseline and every three weeks throughout the 18-week study period. Data were analysed using a mixed model ANOVA. Results: The six weeks of group tai chi followed by another six weeks of home tai chi training showed significant improvements in mean overall knee pain (P = 0.0078), maximum knee pain (P = 0.0035) and the WOMAC subscales of physical function (P = 0.0075) and stiffness (P = 0.0206) compared to the baseline. No significant change of any outcome measure was noted in the attention control group throughout the study. The tai chi group reported lower overall pain and better WOMAC physical function than the attention control group at weeks 9 and 12. All improvements disappeared after detraining.

An Analytical and Experimental Study of Falling-Film Evaporation on a Horizontal Tube

On propose deux modeles, tous les deux bases sur la definition de trois regions de transfert thermique. Etude experimentale mettant en evidence les effets des differents parametres sur le coefficient de transfert thermique

Dietary polyphenols and mechanisms of osteoarthritis

Osteoarthritis is a condition caused in part by injury, loss of cartilage structure and function, and an imbalance in inflammatory and anti-inflammatory pathways. It primarily affects the articular cartilage and subchondral bone of synovial joints and results in joint failure, leading to pain upon weight bearing including walking and standing. There is no cure for osteoarthritis, as it is very difficult to restore the cartilage once it is destroyed. The goals of treatment are to relieve pain, maintain or improve joint mobility, increase the strength of the joints and minimize the disabling effects of the disease. Recent studies have shown an association between dietary polyphenols and the prevention of osteoarthritis-related musculoskeletal inflammation. This review discusses the effects of commonly consumed polyphenols, including curcumin, epigallocatechin gallate and green tea extract, resveratrol, nobiletin and citrus fruits, pomegranate, as well as genistein and soy protein, on osteoarthritis with an emphasis on molecular antiosteoarthritic mechanisms.

Fruits and dietary phytochemicals in bone protection

Osteoporosis is a disease of bone characterized by loss of bone matrix and deterioration of bone microstructure that leads to an increased risk of fracture. Cross-sectional studies have shown a positive association between higher fruit intake and higher bone mineral density. In this review, we evaluated animal and cellular studies of dried plum and citrus and berry fruits and bioactive compounds including lycopene, phenolics, favonoids, resveratrol, phloridzin, and pectin derived from tomato, grapes, apples, and citrus fruits. In addition, human studies of dried plum and lycopene were reviewed. Animal studies strongly suggest that commonly consumed antioxidant-rich fruits have a pronounced effect on bone, as shown by higher bone mass, trabecular bone volume, number, and thickness, and lower trabecular separation through enhancing bone formation and suppressing bone resorption, resulting in greater bone strength. Such osteoprotective effects seem to be mediated via antioxidant or anti-inflammatory pathways and their downstream signaling mechanisms, leading to osteoblast mineralization and osteoclast inactivation. In future studies, randomized controlled trials are warranted to extend the bone-protective activity of fruits and their bioactive compounds. Mechanistic studies are needed to differentiate the roles of phytochemicals and other constitutes in bone protection offered by the fruits. Advanced imaging technology will determine the effective doses of phytochemicals and their metabolites in improving bone mass, microarchitecture integrity, and bone strength, which is a critical step in translating the benefits of fruit consumption on osteoporosis into clinical data.

Green tea polyphenols mitigate deterioration of bone microarchitecture in middle-aged female rats.

Our previous study demonstrated that green tea polyphenols (GTP) benefit bone health in middle-aged female rats without (sham, SH) and with ovariectomy (OVX), because of GTPs antioxidant capacity. The current study further evaluates whether GTP can restore bone micro-structure in both gonad-intact and gonadal-hormone-deficient middle-aged female rats. A 16-week study was performed based on a 2 (SH vs. OVX)x3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n=10/group). An additional 10 rats were euthanized at the beginning of study to provide baseline parameters. Analysis using dual-energy X-ray absorptiometry, histomorphometry, and micro-computed tomography showed that GTP supplementation resulted in (a) increased trabecular volume, thickness, number, and bone formation of proximal tibia, periosteal bone formation rate of tibia shaft, and cortical thickness and area of femur, and (b) decreased trabecular separation and bone erosion of proximal tibia, and endocortical bone eroded surface of tibia shaft. We concluded that drinking water supplemented with GTP mitigated deterioration of bone microarchitecture in both intact and ovariectomized middle-aged female rats by suppressing bone erosion, enhancing bone formation, and modulating endocortical and cancellous bone compartments, resulting in a larger net bone volume.

Green Tea and Bone Health: Evidence from Laboratory Studies

Osteoporosis is a major health problem in the elderly. Epidemiological evidence has shown an association between tea consumption and the prevention of bone loss in the elderly population. Ingestion of green tea and green tea bioactive compounds may be beneficial in mitigating bone loss of this population and decreasing their risk of osteoporotic fractures. This review describes the effect of green tea with its bioactive components on bone health with an emphasis on the following: (i) the etiology of osteoporosis, (ii) evidence of osteo-protective impacts of green tea on bone mass and microarchitecture in various bone loss models in which induced by aging, sex hormone deficiency, and chronic inflammation, (iii) discussion of impacts of green tea on bone mass in two obesity models, (iv) observation of short-term green tea supplementation given to postmenopausal women with low bone mass, (v) possible mechanisms for the osteo-protective effects of green tea bioactive compounds, and (vi) a summary and future research direction of green tea and bone health.

Green tea polyphenols benefits body composition and improves bone quality in long-term high-fat diet-induced obese rats.

This study investigates the effects of green tea polyphenols (GTPs) on body composition and bone properties along with mechanisms in obese female rats. Thirty-six 3-month-old Sprague Dawley female rats were fed either a low-fat (LF) or a high-fat (HF) diet for 4 months. Animals in the LF diet group continued on an LF diet for additional 4 months, whereas those in the HF diet group were divided into 2 groups: with GTP (0.5%) or without in drinking water, in addition to an HF diet for another 4 months. Body composition, femur bone mass and strength, serum endocrine and proinflammatory cytokines, and liver glutathione peroxidase (GPX) protein expression were determined. We hypothesized that supplementation of GTP in drinking water would benefit body composition, enhance bone quality, and suppress obesity-related endocrines in HF diet-induced obese female rats and that such changes are related to an elevation of antioxidant capacity and a reduction of proinflammatory cytokine production. After 8 months, compared with the LF diet, the HF diet increased percentage of fat mass and serum insulin-like growth factor I and leptin levels; reduced percentage of fat-free mass, bone strength, and GPX protein expression; but had no effect on bone mineral density and serum adiponectin levels in the rats. Green tea polyphenol supplementation increased percentage of fat-free mass, bone mineral density and strength, and GPX protein expression and decreased percentage of fat mass, serum insulin-like growth factor I, leptin, adiponectin, and proinflammatory cytokines in the obese rats. This study shows that GTP supplementation benefited body composition and bone properties in obese rats possibly through enhancing antioxidant capacity and suppressing inflammation.

Green tea polyphenols supplementation and Tai Chi exercise for postmenopausal osteopenic women: safety and quality of life report

BackgroundEvidence suggests that both green tea polyphenols (GTP) and Tai Chi (TC) exercise may benefit bone health in osteopenic women. However, their safety in this population has never been systematically investigated. In particular, there have been hepatotoxicity concerns related to green tea extract. This study was to evaluate the safety of 24 weeks of GTP supplementation combined with TC exercise in postmenopausal osteopenic women, along with effects on quality of life in this population.Methods171 postmenopausal women with osteopenia were randomly assigned to 4 treatment arms for 24 weeks: (1) Placebo (500 mg starch/day), (2) GTP (500 mg GTP/day), (3) Placebo + TC (placebo plus TC training at 60 min/session, 3 sessions/week), and (4) GTP + TC (GTP plus TC training). Safety was examined by assessing liver enzymes (aspartate aminotransferase, alanine aminotransferase), alkaline phosphatase, and total bilirubin at baseline and every 4 weeks. Kidney function (urea nitrogen and creatinine), calcium, and inorganic phosphorus were also assessed at the same times. Qualify of life using SF-36 questionnaire was evaluated at baseline, 12, and 24 weeks. A mixed model of repeated measures ANOVA was applied for analysis.Results150 subjects completed the study (12% attrition rate). The compliance rates for study agents and TC exercise were 89% and 83%, respectively. Neither GTP supplementation nor TC exercise affected liver or kidney function parameters throughout the study. No adverse event due to study treatment was reported by the participants. TC exercise significantly improved the scores for role-emotional and mental health of subjects, while no effect on quality of life was observed due to GTP supplementation.ConclusionsGTP at a dose of 500 mg/day and/or TC exercise at 3 hr/week for 24 weeks appear to be safe in postmenopausal osteopenic women, particularly in terms of liver and kidney functions. TC exercise for 24 weeks (3 hr/wk) significantly improved quality of life in terms of role-emotional and mental health in these subjects. ClinicalTrials.gov identifier: NCT00625391.

Tea and bone health: steps forward in translational nutrition

Osteoporosis is a major health problem in the aging population worldwide. Cross-sectional and retrospective evidence indicates that tea consumption may be a promising approach in mitigating bone loss and in reducing risk of osteoporotic fractures among older adults. Tea polyphenols enhance osteoblastogenesis and suppress osteoclastogenesis in vitro. Animal studies reveal that intake of tea polyphenols have pronounced positive effects on bone as shown by higher bone mass and trabecular bone volume, number, and thickness and lower trabecular separation via increasing bone formation and inhibition of bone resorption, resulting in greater bone strength. These osteoprotective effects appear to be mediated through antioxidant or antiinflammatory pathways along with their downstream signaling mechanisms. A short-term clinical trial of green tea polyphenols has translated the findings from ovariectomized animals to postmenopausal osteopenic women through evaluation of bioavailability, safety, bone turnover markers, muscle strength, and quality of life. For future studies, preclinical animal studies to optimize the dose of tea polyphenols for maximum osteoprotective efficacy and a follow-up short-term dose-response trial in postmenopausal osteopenic women are necessary to inform the design of randomized controlled studies in at-risk populations. Advanced imaging technology should also contribute to determining the effective dose of tea polyphenols in achieving better bone mass, microarchitecture integrity, and bone strength, which are critical steps for translating the putative benefit of tea consumption in osteoporosis management into clinical practice and dietary guidelines.