Project description:The performance of three widely used thermal radiation models, the P-1 model, the surface-to-surface (S2S) model and the Discrete-Ordinates (DO) model, were evaluated for simulation temperature in Chinses solar greenhouse. The thermal radiation models were evaluated by comparing the numerical results with experimental data at representative points in the CSG. For indoor rear wall, the indoor soil and indoor air, the models showed good agreement between the experimental data and the simulated results correspond to P1, S2S and DO respectively. This work provides information for simulate greenhouse temperature and use specific radiation models for the most suitable thermal environment for crop growth.
Project description:In order to further improve the utilization of solar energy in Chinese Solar Greenhouse (CSG), this paper systematically studied the effects of orientation and structure on solar radiation interception in CSG. A solar radiation model has been developed based on the previous research, which taking solar motion law, meteorological data, and optical properties of materials into consideration. The established model was used to optimize the orientation and structure of CSG. The analysis of structure considered two major structural parameters, which are the ridge height and the horizontal projection of the rear roof. Moreover, the widely used Liao-Shen type Chinese solar greenhouse (CSG-LS) has been taken as the prototype in the present research, and the measured data of the typical clear day was used for the model validation. The results showed that the ridge height has a remarkable influence on the solar energy captured by CSG-LS. Compared with the optimization of a single factor, the comprehensive optimization of orientation and structure can increase the solar radiation interception of the rear wall by 3.95%. Considering the limiting factor of heat storage-release capacity and the shading effect on the greenhouse structure, the optimal lighting construction of the CSG-LS (with a span of 9.0 m) was specified as 7~9° from south to west of azimuth angle, 4.5~4.7 m ridge height, and 1.4~1.6 m horizontal projection of the rear roof at 42°N latitude. The proposed solar radiation model can provide scientific guidance for the CSG-LS construction in different areas.
Project description:In order to optimize the heat preservation capacity of Chinese solar greenhouse (CSG) and further reduce energy consumption, we clarified the mechanism of the external thermal insulation layer that affects the microclimate environment of CSG. The most suitable external insulation layer thickness (EILT) of the solar greenhouse envelope structure in high latitude and cold region has been indicated. A three-dimensional mathematical model was developed based on computational fluid dynamics and verified using experimental measurement. The temperature variations, heat variations and economic benefit were analysed. The results indicated that covering the outer surface of the enclosures with a thermal insulation layer could effectively increase the greenhouse temperature by 1.2-4.0°C. The influence degree of the external thermal insulation layer on the greenhouse microclimate was as follows: sidewall (SW) > north wall (NW) > north roof (NR). In high-dimensional and cold areas, covering the outer surface of all enclosures with insulation layer as the suitable solution could raise the greenhouse air temperature maximally. The suitable EILT of each maintenance structure was obtained as follows: NW 80 mm, SW 80 mm, NR 100 mm.
Project description:A cohort study of cucumber greenhouse workers’ exposure to fungi and bacteria as measured using NGS and MALDI-TOF MS and their serum levels of serum amyloid A and C-reactive protein and association to work tasks
Project description:This paper clarified the mechanism of the south and north roofs' effect on the thermal environment of the Chinese solar greenhouse (CSG), using a new parameter: ridge position ratio (RPR), which can describe the dynamic dependency relationship between the south and north roofs. A mathematical model was established using a method of combining computational fluid dynamics (CFD) simulation with experiments, then the model was used to further analyse the effect of RPR on the thermal environment of the CSG. The experimental greenhouse was simulated as an empty building to obtain results independently from these factors including crop and ventilation conditions. The results showed that the occurrence time of the maximum air temperature will be delayed when RPR increases to 0.3 during the daytime. As RPR increases, the heat storage layer of the soil gradually becomes thinner, but the north wall remains unchanged. RPR has a relatively small effect on the minimum temperature of each greenhouse part during the night. Mathematical models of the relationships between RPR, the solar energy that entered the greenhouse and the released heat energy of the enclosure structures were established, respectively. This paper can provide theoretical guidance for the structural design of the CSG.
Project description:BackgroundFrom animal studies it is known that currently used pesticides can disturb thyroid function.MethodsIn the present study we investigated the thyroid function in 122 Danish greenhouse workers, to evaluate if greenhouse workers classified as highly exposed to pesticides experiences altered thyroid levels compared to greenhouse workers with lower exposure. Serum samples from the greenhouse workers were sampled both in the spring and the fall to evaluate if differences in pesticide use between seasons resulted in altered thyroid hormone levels.ResultsWe found a moderate reduction of free thyroxine (FT4) (10-16%) among the persons working in greenhouses with a high spraying load both in samples collected in the spring and the fall, but none of the other measured thyroid hormones differed significantly between exposure groups in the cross-sectional comparisons. However, in longitudinal analysis of the individual thyroid hormone level between the spring and the fall, more pronounced differences where found with on average 32% higher thyroid stimulating hormone (TSH) level in the spring compared to the fall and at the same time a 5-9% lower total triiodthyroxin (TT3), free triiodthyroxine (FT3) and FT4. The difference between seasons was not consistently more pronounced in the group classified as high exposure compared to the low exposure groups.ConclusionThe present study indicates that pesticide exposure among Danish greenhouse workers results in only minor disturbances of thyroid hormone levels.
Project description:Scabies is endemic in many resource-poor tropical areas, causing significant morbidity. However, our understanding of the true burden of scabies in Africa is limited, partly owing to limited capacity and challenges accessing the currently recommended diagnostic tools. The primary objective of this study was to assess the diagnostic accuracy of scabies assessments made by minimally trained field-workers. We trained field-workers with a minimum of secondary school education in the diagnosis of scabies. After the training, we assessed the diagnostic accuracy of assessments made by nine field-workers compared with the reference standard. In all, 193 individuals were assessed for scabies. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated, as well as agreement (κ coefficients) between medical doctors and between field-workers. Of the 193 participants, 26% had scabies according to the reference standard. The sensitivity of field-worker diagnosis compared with the reference standard was 94% (95% CI: 90-99%), and the specificity was 96% (95% CI: 90-97%). The determination of severity by field-workers was less accurate; the sensitivity for severe scabies was 61% (95% CI: 48-74%), and the mean specificity was 97% (95% CI: 93-100%). This study demonstrated that field-workers without medical qualifications were capable of diagnosing scabies to a similar level of accuracy as experienced medical doctors after a short period of focal training. This may facilitate rapid assessments of scabies prevalence for public health purposes and decisions about mass drug administration implementation in similar settings.
Project description:ObjectiveThe euglycemic-hyperinsulinemic clamp is the gold standard to evaluate insulin resistance (IR), but there are only a few studies on the prevalence of IR in Chinese Han women with polycystic ovary syndrome (PCOS). This study investigated: (a) the prevalence of IR in Chinese Han women with PCOS by clamp, (b) the degree of reduction in insulin sensitivity (IS) and the contribution of body mass index (BMI).DesignRetrospective cross-sectional analysis.PatientsChinese Han women with PCOS (n = 448) visiting the Department of Endocrinology or the Department of Obstetrics and Gynaecology of the First Affiliated Hospital of Chongqing Medical University. Chinese Han women without PCOS (controls) from the same area (n = 40).MeasurementsClamp-measured IS, age, BMI, and total testosterone.ResultsThe prevalence of IR and reduction in IS were 56.3% and 30.3%, respectively, in Chinese Han women with PCOS (both P < 0.001). The inherent reduction in IS was 18.8% in lean women with PCOS and BMI independently reduced IS by 37.9% in obese women with PCOS. The prevalence of IR estimated by homeostatic model assessment (HOMA) was lower than that determined by clamp. The multivariable analysis showed that IR by clamp (R2 = 0.48, P < 0.001) was independently associated with BMI (β = -0.52, P < 0.001), waist-hip ratio (β = -0.23, P < 0.001), total testosterone (β = -0.07, P = 0.045) and age (β = 0.17, P < 0.001), while IR by HOMA was only associated with BMI (R2 = 0.25, β = 0.50, P < 0.001). There were no differences in BMI groups distribution, HOMA-IR and M values among the four PCOS subtypes (all P > 0.05).Conclusions56.3% of Chinese Han women with PCOS had IR and their reduction in IS was 30.3%. Obesity exacerbated the reduction in IS. When being evaluated by HOMA, the prevalence and the risk factors of IR in Chinese women with PCOS were underestimated.
Project description:Over the span of nearly 10 years, the social work labor force grew from 0.2 million to approximately 1.2 million in China. Despite these increases, studies have shown social workers in China are also experiencing equally high burnout rates. For this analysis, we collected data from 537 social workers based in Guangzhou, China. We used the job demands and resources (JD-R) theory, to examine the relations between JD-R and burnout and whether mindfulness practice (MP) could reduce any such burnout. Our results suggest JD-R affects social workers' burnout through both health and motivation impairment. High job demands (JD) were linked to high burnout while high job resources (JR) were linked to a reduction in burnout. Formal (Beta = -0.08) and informal (Beta = -0.19) MP were associated with low burnout amongst social workers. The significant interaction between JD and MP also suggests that MP can reduce burnout for social workers with high JD. The findings call for using MP to be used to shield social workers from the effects of increasing JD and to prevent an increase of burnout amongst Chinese social workers.