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Animal studies have shown that capsaicin plays a positive role in weight management. However, the results in human research are controversial. Therefore, the present systematic review and meta-analysis aimed to evaluate the effect of capsaicin on weight loss in adults. We searched PubMed, Embase, China Biomedical Literature Database (CBM), Cochrane library and clinical registration centre, identifying all randomised controlled trials (RCT) published in English and Chinese to 3 May 2022. A random-effect model was used to calculate the weighted mean difference (WMD) and 95 % CI. Heterogeneity between studies was assessed by the Cochran Q statistic and I-squared tests (I2). Statistical analyses were performed using STATA version 15.1. P-values < 0·05 were considered as statistically significant. From 2377 retrieved studies, fifteen studies were finally included in the meta-analyses. Fifteen RCT with 762 individuals were included in our meta-analysis. Compared with the control group, the supplementation of capsaicin resulted in significant reduction on BMI (WMD: −0·25 kg/m2, 95 % CI = –0·35, –0·15 kg/m2, P < 0·05), body weight (BW) (WMD: −0·51 kg, 95 % CI = –0·86, –0·15 kg, P < 0·05) and waist circumference (WC) (WMD: −1·12 cm, 95 % CI = –2·00, –0·24 cm, P < 0·05). We found no detrimental effect of capsaicin on waist-to-hip ratio (WMD: −0·05, 95 % CI = –0·17, 0·06, P > 0·05). The current meta-analysis suggests that capsaicin supplementation may have rather modest effects in reducing BMI, BW and WC for overweight or obese individuals.
Intertemporal choices involve tradeoffs between outcomes that occur at different times. Most of the research has used pure gains tasks and the discount rates yielding from those tasks to explain and predict real-world behaviors and consequences. However, real decisions are often more complex and involve mixed outcomes (e.g., sooner-gain and later-loss or sooner-loss and later-gain). No study has used mixed gain-loss intertemporal tradeoff tasks to explain and predict real-world behaviors and consequences, and studies involving such tasks are also scarce. Considering that tasks involving a combination of gains and losses may yield different discount rates and that existing pure gains tasks do not explain or predict real-world outcomes well, this study conducted two experiments to compare the discount rates of mixed gain-loss intertemporal tradeoffs with those of pure gains or pure losses (Experiment 1) and to examine whether these tasks predicted different real-world behaviors and consequences (Experiment 2). Experiment 1 suggests that the discount rate ordering of the four tasks was, from highest to lowest, pure gains, sooner-loss and later-gain, pure losses, and sooner-gain and later-loss. Experiment 2 indicates that the evidence supporting the claim that the discount rates of the four tasks were related to different real-world behaviors and consequences was insufficient.
It has been suggested that added sugar intake is associated with non-alcoholic fatty liver disease (NAFLD). However, previous studies only focused on sugar-sweetened beverages; the evidence for associations with total added sugars and their sources is scarce. This study aimed to examine the associations of total added sugars, their physical forms (liquid v. solid) and food sources with risk of NAFLD among adults in Tianjin, China. We used data from 15 538 participants, free of NAFLD, other liver diseases, CVD, cancer or diabetes at baseline (2013–2018 years). Added sugar intake was estimated from a validated 100-item FFQ. NAFLD was diagnosed by ultrasonography after exclusion of other causes of liver diseases. Multivariable Cox proportional hazards models were fitted to calculate hazard ratios (HR) and corresponding 95 % CI for NAFLD risk with added sugar intake. During a median follow-up of 4·2 years, 3476 incident NAFLD cases were documented. After adjusting for age, sex, BMI and its change from baseline to follow-up, lifestyle factors, personal and family medical history and overall diet quality, the multivariable HR of NAFLD risk were 1·18 (95 % CI 1·06, 1·32) for total added sugars, 1·20 (95 % CI 1·08, 1·33) for liquid added sugars and 0·96 (95 % CI 0·86, 1·07) for solid added sugars when comparing the highest quartiles of intake with the lowest quartiles of intake. In this prospective cohort of Chinese adults, higher intakes of total added sugars and liquid added sugars, but not solid added sugars, were associated with a higher risk of NAFLD.
Prospective cohort studies linking organ meat consumption and non-alcoholic fatty liver disease (NAFLD) are limited, especially in Asian populations. This study aimed to prospectively investigate the association between organ meat consumption and risk of NAFLD in a general Chinese adult population. This prospective cohort study included a total of 15 568 adults who were free of liver disease, CVD and cancer at baseline. Dietary information was collected at baseline using a validated FFQ. NAFLD was diagnosed by abdominal ultrasound after excluding other causes related to chronic liver disease. Cox proportional regression models were used to assess the association between organ meat consumption and risk of NAFLD. During a median of 4·2 years of follow-up, we identified 3604 incident NAFLD cases. After adjusting for demographic characteristics, lifestyle factors, vegetable, fruit, soft drink, seafood and red meat consumption, the multivariable hazard ratios (95 % CI) for incident NAFLD across consumption of organ meat were 1·00 (reference) for almost never, 1·04 (0·94, 1·15) for tertile 1, 1·08 (0·99, 1·19) for tertile 2 and 1·11 (1·01, 1·22) for tertile 3, respectively (Pfor trend < 0·05). Such association did not differ substantially in the sensitivity analysis. Our study indicates that organ meat consumption was related to a modestly higher risk of NAFLD among Chinese adults. Further investigations are needed to confirm this finding.
High dietary fibre intake has been associated with a lower risk of diabetes, but the association of dietary fibre with prediabetes is only speculative, especially in China, where the supportive data from prospective studies are lacking. This study aimed to examine the association between dietary fibre intake and risk of incident prediabetes among Chinese adults. We performed a prospective analysis in 18 085 participants of the Tianjin Chronic Low-grade Systemic Inflammation and Health cohort study who were free of diabetes, prediabetes, cancer and CVD at baseline. Dietary data were collected using a validated 100-item FFQ. Prediabetes was defined based on the American Diabetes Association diagnostic criteria. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95 % CI. During 63 175 person-years of follow-up, 4139 cases of incident prediabetes occurred. The multivariable HR of prediabetes for the highest v. lowest quartiles were 0·85 (95 % CI 0·75, 0·98) (P for trend = 0·02) for total dietary fibre, 0·84 (95 % CI 0·74, 0·95) (P for trend < 0·01) for soluble fibre and 1·05 (95 % CI 0·93, 1·19) (P for trend = 0·38) for insoluble fibre. Fibre from fruits but not from cereals, beans and vegetables was inversely associated with prediabetes. Our results indicate that intakes of total dietary fibre, soluble fibre and fibre derived from fruit sources were associated with a lower risk of prediabetes.
Seaweeds have numerous biologically active ingredients, such as polysaccharides, polyphenols and carotenoids, that are beneficial to human health. Although these benefits might be related to the synthesis, secretion or reabsorption of uric acid, no studies have explored the relationship between seaweeds consumption and hyperuricaemia (HUA) in the general population. The aim of this study was to investigate whether seaweeds consumption is related to HUA in a large-scale adult population. A cross-sectional study was conducted with 32 365 adults (17 328 men and 15 037 women) in Tianjin, People’s Republic of China. Frequency of seaweeds consumption was assessed by a validated self-administered FFQ. HUA was defined as serum uric acid levels >420 μmol/L in men and >350 μmol/L in women. The association between seaweeds consumption and HUA was assessed by multiple logistic regression analysis. Restricted cubic spline functions were used for non-linearity tests. The prevalence of HUA in men and women was 21·17 % and 5·93 %, respectively. After adjustments for potential confounding factors, the OR (95 % CI) for HUA across seaweed consumption (g/1000 kcal per d) were 1·00 (reference) for level 1, 0·91 (95 % CI 0·81, 1·02) for level 2; 0·90 (95 % CI 0·81, 1·01) for level 3; 0·86 (95 % CI 0·78, 0·97) for level 4 in men and 0·90 (95 % CI 0·73, 1·10) for level 2; 0·82 (95 % CI 0·67, 1·00) for level 3; 0·84 (95 % CI 0·68, 1·03) for level 4 in women, respectively. A negative correlation between seaweeds consumption and HUA in males but not in females was observed. Further studies are needed to explore the causal relationship.
This cross-sectional study aimed to examine the associations between dietary fibre (DF) intake and depressive symptoms in a general adult population in Tianjin, China. A total of 24 306 participants (mean age 41 years; range 18–91 years) were enrolled. DF intake was assessed using a validated self-administered FFQ. Depressive symptoms were assessed using the Self-Rating Depression Scale. Associations between DF intake and depressive symptoms were estimated using logistic regression analysis. Socio-demographic, behavioural, health status and dietary factors were adjusted. In men, compared with participants in the lowest quartiles for total, soluble, vegetable and soya DF, OR for depressive symptoms in the highest were 0·83 (95 % CI 0·69, 0·99), 0·74 (95 % CI 0·63, 0·87), 0·79 (95 % CI 0·65, 0·96) and 0·69 (95 % CI 0·60, 0·81), respectively. In women, compared with participants in the lowest quartiles for vegetable and soya DF, the OR for depressive symptoms in the highest were 0·77 (95 % CI 0·64, 0·93) and 0·82 (95 % CI 0·70, 0·95), respectively. No association was found between total or soluble DF intake and depressive symptoms in women. No association was found between insoluble, cereal, fruit or tuber DF intake and depressive symptoms in men and women. Linear associations between DF intake and depressive symptoms were only detected for soya DF (men, β = –0·148, P < 0·0001; women, β = –0·069, P = 0·04). Results suggest that intake of soluble, vegetable and soya DF was inversely associated with depressive symptoms. These results should be confirmed through prospective and interventional studies.
Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Recent evidence has suggested the protective effects of honey consumption against the metabolic syndrome, but the association between honey intake and NAFLD is still unclear. We investigated how the consumption frequency of honey was associated with NAFLD in the general population. This was a cross-sectional study of 21 979 adults aged 20–90 years. NAFLD was diagnosed based on the ultrasound-diagnosed fatty liver without significant alcohol intake and other liver diseases. Diet information, including consumption frequency of honey, was assessed by a validated 100-item FFQ. OR with 95 % CI were calculated by the binary logistic regression model, adjusting for confounding factors identified by the directed acyclic graph. Overall, 6513 adults (29·6 %) had NAFLD. Compared with participants consuming ≤1 time/week of honey, the multivariable OR of NAFLD were 0·86 (95 % CI 0·77, 0·97) for 2–6 times/week and 1·10 (95 % CI 0·95, 1·27) for ≥1 times/d (Pfor trend = 0·90). The results were generally similar in subgroups of BMI at a cut-point of 24·0 kg/m2 (Pfor interaction = 0·10). In this large-scale study, consuming honey 2–6 times/week was inversely associated with NAFLD, whereas consuming honey ≥1 times/d had no association with NAFLD. These results need replication in other large-scale prospective studies.
Clonorchis sinensis (C. sinensis) is one of the most serious food-borne parasites, which can lead to liver fibrosis or cholangiocarcinoma. Effective measures for clonorchiasis prevention are still urgently needed. Bacillus subtilis (B. subtilis) is an effective antigen delivery platform for oral vaccines. Chonorchis sinensis serpin (CsSerpin) was proved to be potential vaccine candidates. In this study, CsSerpin3 was displayed on the surface of B. subtilis spore and recombinant spores were orally administrated to BALB/C mice. CsSerpin3-specific IgA levels in faecal, bile and intestinal mucous increased at 4–8 weeks after the first administration compared with those in control groups. The mucus production and the number of goblet cells in intestinal mucosa elevated in B.s-CotC-CsSerpin3 (CotC, coat protein of B. subtilis spore) spores treated group compared to those in blank control. No significant difference in the activities of glutamic-pyruvic transaminase/ alanine aminotransferase and glutamic oxalacetic transaminase/aspartate aminotransferase were observed between groups. There was no side effect inflammation and observable pathological damage in the liver tissue of mice after administration. Moreover, collagen deposition and Ishak score were statistically reduced in B.s-CotC-CsSerpin3 spores treated mice. In conclusion, B. subtilis spores displaying CsSerpin3 could be investigated further as an oral vaccine against clonorchiasis.
Evidence has suggested that honey intake has a beneficial impact on glycaemic control in patients with type 2 diabetes. Whether these findings apply to adults with prediabetes is yet unclear. The aim of the present study was to examine whether honey intake is associated with a lower prevalence of prediabetes. A cross-sectional study was performed in 18 281 participants (mean age 39·6 (sd 11·1) years; men, 51·5 %). Dietary intake was assessed through a validated 100-item FFQ. Prediabetes was defined according to the American Diabetes Association criteria: impaired fasting glucose, impaired glucose tolerance or raised glycosylated Hb. Multivariable logistic regression models were used to estimate the association between honey consumption and prediabetes. As compared with those who almost never consumed honey, the multivariable OR of prediabetes were 0·94 (95 % CI 0·86, 1·02) for ≤3 times/week, 0·77 (95 % CI 0·63, 0·94) for 4–6 times/week and 0·85 (95 % CI 0·73, 0·99) for ≥1 time/d (Pfor trend < 0·01). These associations did not differ substantially in sensitivity analysis. Higher honey consumption was associated with a decreased prevalence of prediabetes. More large prospective cohort studies are needed to investigate this association.
Animal studies have suggested that mushroom intake can alleviate non-alcoholic fatty liver disease (NAFLD) due to its anti-inflammatory and antioxidant properties. However, the association between mushroom intake and NAFLD is unknown in humans. We aimed to investigate the association of mushroom intake with NAFLD among Chinese adults. This is a cross-sectional study of 24 236 adults (mean (standard deviation) age: 40·7 (sd 11·9) years; 11 394 men (47·0 %)). Mushroom intake was assessed via a validated FFQ. Newly diagnosed NAFLD was identified based on the results of annual health examinations, including ultrasound findings and a self-reported history of the disease. Multiple logistic models were used to examine the association between mushroom intake and NAFLD. The prevalence of newly diagnosed NAFLD was 19·0 %. Compared with those consuming mushrooms less frequently (≤1 time/week), the fully adjusted OR of newly diagnosed NAFLD were 0·95 (95 % CI 0·86, 1·05) for those consuming 2–3 times/week and 0·76 (95 % CI 0·63, 0·92) for those consuming ≥4 times/week (Pfor trend = 0·01). The inverse association was consistent in subgroups defined by age, sex and BMI. In conclusion, higher mushroom intake was significantly associated with lower prevalence of NAFLD among Chinese adults. Future research is required to understand the causal association between mushroom intake and NAFLD.
Many components in diet have regulated oxidative stress, inflammatory reaction and even balance oestrogen levels. Because these factors are closely associated with depressive symptoms in postmenopausal women, it is considered that dietary factors are able to prevent and control depressive symptoms. On the other hand, a dietary pattern that considers the correlations and synergies between foods and nutrients is expected to have a greater impact on disease risk. The aim of the present study is to evaluate whether dietary patterns are associated with depressive symptoms in Chinese postmenopausal women. A cross-sectional study of 2051 postmenopausal women (mean age: 58·8 (sd 7·4) years) was conducted in Tianjin, China. Dietary consumption was assessed by a valid self-administered FFQ. Principal component analysis was used to derive three major dietary patterns: ‘healthy’, ‘sweets’ and ‘traditional Tianjin’ from eighty-eight food items. Depressive symptoms were assessed using the Zung Self-Rating Depression Scale, and cut-off point of 48 indicating serious depressive symptoms. The association between quartile of dietary patterns and depressive symptoms was assessed using multiple logistic regression analysis. The multivariable-adjusted OR of having depressive symptoms for increasing quartile of dietary patterns were as follows: healthy, 1·00, 0·79 (95 % CI 0·49, 1·28), 0·62 (95 % CI 0·37, 1·04) and 0·57 (95 % CI 0·33, 0·97); sweets, 1·00, 0·75 (95 % CI 0·42, 1·3), 1·08 (95 % CI 0·64, 1·81) and 1·66 (95 % CI 1·03, 2·71); and traditional Tianjin, 1·00, 1·02 (95 % CI 0·58, 1·79), 0·96 (95 % CI 0·54, 1·71) and 2·53 (95 % CI 1·58, 4·16), respectively. The present study demonstrated that a healthy dietary pattern was inversely associated with depressive symptoms. On the contrary, greater adherence to sweets and traditional Tianjin dietary patterns was associated with a higher prevalence of depressive symptoms.
Previous studies have indicated that some food items and nutrients are associated with uric acid metabolism in humans. However, little is known about the role of dietary patterns in hyperuricaemia. We designed this case–control study to evaluate the associations between dietary patterns and newly diagnosed hyperuricaemia in Chinese adults. A total of 1422 cases and 1422 controls were generated from 14 538 participants using the 1:1 ratio propensity score matching methods. Dietary intake was assessed using a validated self-administered FFQ. Dietary patterns were derived by factor analysis. Hyperuricaemia was defined as concentrations of serum uric acid higher than 7 mg/dl (416·5 μmol/l) for men and 6 mg/dl (357 μmol/l) for women. Three dietary patterns were derived by factor analysis: sweet pattern; vegetable pattern; animal foods pattern. The animal foods pattern characterised by higher intake of an animal organ, seafood and processed meat products was associated with higher prevalence of newly diagnosed hyperuricaemia (Pfor trend<0·01) after adjustment. Compared with the participants in the lowest quartile of the animal foods pattern, the OR of newly diagnosed hyperuricaemia in the highest quartile was 1·50 (95 % CI 1·20, 1·87). The other two dietary patterns were not associated with the prevalence of newly diagnosed hyperuricaemia after adjustment. In conclusion, a diet rich in animal organ, seafood and processed meat products is associated with higher prevalence of newly diagnosed hyperuricaemia in a Chinese population. Further cohort studies and randomised controlled trials are required to clarify these findings.
Previous studies have demonstrated adverse mental health effects of Pb exposure. The purpose of this study is to investigate the relationship between consumption of preserved egg (PE), a high-Pb-containing food and depressive symptoms among adults in China. A sample of 25 213 adults (mean age 41·4 (sd 11·8) years; males, 53·9 %) in Tianjin, China, was studied in a cross-sectional analysis. Dietary intake including PE was assessed using a valid self-administered FFQ. Depressive symptoms were assessed using the Self-Rating Depression Scale (SDS). The association was estimated by OR using logistic regression models adjusted for multiple confounders. The prevalence of elevated depressive symptoms was 6·6 % (SDS≥50). Compared with the least frequent PE consumption (<once/week), multivariable adjusted OR for elevated depressive symptoms were 1·52 (95 % CI 1·28, 1·81), 2·24 (95 % CI 1·76, 2·81) and 3·31 (95 % CI 2·52, 4·30) for consumption of once, 2–3 times and ≥4 times/week, respectively (Pfor trend<0·0001), indicating a clear dose–response relationship. The results suggested that higher consumption of PE was strongly associated with depressive symptoms among adults in China. These findings underscore the need to consider dietary Pb exposure as a risk factor for psychological distress.
Previous studies have supported the theory that there is a positive association between ferritin and carotid atherosclerosis in Western people. Diet plays an important role in determining serum ferritin concentration. Asian dietary patterns are different from Western dietary patterns, implying that there may be a difference in the association of ferritin with carotid atherosclerosis between Asian and Western people. However, few studies focus on the association between ferritin and carotid atherosclerosis among Asians. The aim of this study was to investigate how serum ferritin levels are associated with carotid atherosclerosis in an Asian adult population. A cross-sectional assessment was performed in 8302 adults in Tianjin, China. Carotid intima-media thickness (IMT) and plaques were assessed using ultrasonography, and serum ferritin was measured using the protein chip-chemiluminescence method. Multiple logistic regression analysis was used to examine the association between quartiles of serum ferritin concentration and carotid atherosclerosis. In the present study, the overall prevalence of IMT and carotid plaques in participants is 29·2 and 22·7 %, respectively. In women, after adjustments for potentially confounding factors, the OR of IMT and carotid plaques by increasing serum ferritin quartiles were 1·00, 1·39 (95 % CI 0·98–1·99), 1·39 (95 % CI 0·99–1·97), 1·81 (95 % CI 1·30–2·55) (Pfor trend<0·001) and 1·00, 1·24 (95 % CI 0·89–1·73), 1·18 (95 % CI 0·85–1·65), 1·59 (95 % CI 1·15–2·20) (Pfor trend<0·01), respectively. However, no association was found between serum ferritin and carotid atherosclerosis in men. The study demonstrated that increased serum ferritin levels are independently associated with IMT and carotid plaques in Asian women but not in Asian men.
In the present study, we evaluated the reproducibility and validity of dietary patterns among Chinese adult populations. A random subsample of 203 participants (aged 31–80 years) from a community-based nutrition and health survey was enrolled. An eighty-seven-item FFQ was administered twice (FFQ1 and FFQ2) 1 year apart; four 3 consecutive day, 24-h dietary recalls (24-HDR, as a reference method) were performed between the administrations of the two FFQ every 3 months. Dietary patterns from three separate dietary sources were derived using factor analysis based on twenty-eight predefined food groups. Comparisons between dietary pattern scores were made by using Pearson’s or intraclass correlation coefficients (ICC), cross-classification analysis, weighted κ statistic and Bland–Altman plots; the four major dietary patterns identified from FFQ1, FFQ2 and 24-HDR were similar. Regarding reproducibility, ICC for z-scores between FFQ1 and FFQ2 were all >0·6 for dietary patterns. The ‘animal and plant protein’ pattern had the highest ICC of 0·870. For validity, the adjusted Pearson’s correlation coefficients for dietary pattern z-scores between two FFQ and the mean of four 3 consecutive day 24-HDR ranged from 0·387 for the ‘Chinese traditional’ pattern to 0·838 for the ‘animal and plant protein’ pattern. More than 75 % of the participants were classified into the same or adjacent quartile, and <5 % were misclassified into opposite quartiles. The weighted κ ranged from 0·259 to 0·680. Bland–Altman plots indicated that no significant deviation was found between two dietary assessment methods. Our findings indicate a good reasonable reproducibility and a reasonable validity of dietary patterns derived by factor analysis in China.
We evaluated the reproducibility and validity of an FFQ used in a Chinese community-based nutrition and health survey. A total of ninety-nine males and 104 females aged 31–80 years completed four three consecutive 24-h dietary recalls (24-HDR, served as a reference method, one three consecutive 24-HDR for each season) and two FFQ (FFQ1 and FFQ2) over a 1-year interval. The reproducibility of the FFQ was estimated with correlation coefficients, misclassification and weighted κ statistic. The validity was evaluated by comparing the data obtained from FFQ2 with the mean 24-HDR (m24-HDR). Compared with the m24-HDR, the FFQ tended to underestimate intake of most nutrients and food groups. For all nutrients and food groups, the Spearman’s and intra-class correlation coefficients between FFQ1 and FFQ2 ranged from 0·66 to 0·88 and from 0·65 to 0·87, respectively. Most correlation coefficients decreased after adjusting for energy. More than 90 % of the subjects were classified into the same or adjacent categories by both FFQ. For all nutrients and food groups, the crude, energy-adjusted and de-attenuated Spearman’s correlation coefficients between FFQ2 and the m24-HDR ranged from 0·21 to 0·69, 0·19 to 0·58 and 0·25 to 0·71, respectively. More than 70 % of the subjects were classified into the same and adjacent categories by both instruments. Both weighted κ statistic and the Bland–Altman plots showed reasonably acceptable agreement between the FFQ2 and the m24-HDR. The FFQ developed for adults in the Nanjing area can be used to reliably and validly measure usual intake of major nutrients and food groups.
We report an experimental study of the large-scale circulation (LSC) in a turbulent Rayleigh–Bénard convection cell with aspect ratio unity. The temperature-extrema-extraction (TEE) method for obtaining the dynamic information of the LSC is presented. With this method, the azimuthal angular positions of the hot ascending and cold descending flows along the sidewall are identified from the measured instantaneous azimuthal temperature profile. The motion of the LSC is then decomposed into two different modes based on these two angles: the azimuthal mode and the translational or sloshing mode that is perpendicular to the vertical circulation plane of the LSC. Comparing to the previous sinusoidal-fitting (SF) method, it is found that both the TEE and the SF methods give the same information about the azimuthal motion of the LSC, but the TEE method in addition can provide information about the sloshing motion of the LSC. The sloshing motion is found to oscillate time-periodically around the cell's central vertical axis with an amplitude being nearly independent of the turbulent intensity and to have a π/2 phase difference with the torsional mode. It is further found that the azimuthal angular positions of the hot ascending and cold descending flows oscillate out of phase with each other by π, which leads to the observations of the torsional mode when these two flows are near the top and the bottom plates, respectively, and of the sloshing mode when they are both near the mid-height plane. A direct velocity measurement further confirms the existence of the bulk sloshing mode of the flow field.
We present direct multipoint velocity measurements of the two-dimensional velocity field in the central region of turbulent Rayleigh–Bénard convection. The local homogeneity and isotropy of the velocity field are tested using a number of criteria and are found to hold to an excellent degree. The properties of velocity circulation Γr are also studied. The results show that the circulation appears to be more effective in capturing the effect of local anisotropy than the velocity field itself. The distribution of Γr is found to depend on the scale r, reflecting strong intermittency. It is further found that the velocity circulation has the same anomalous scaling exponents as the longitudinal and transverse structure functions for low-order moments (p≲5), whereas, for high-order moments (p≳5), the anomalous scaling exponents for circulation are found to be systematically smaller than the scaling exponents of the longitudinal and transverse structure functions.
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