Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of ...glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem. The results show that the thermal stress at the seal joint is approximately zero, below 0.279 MPa, far below than the bearing range of 40-120 MPa. At the same time, it was also shows that by adding a reflective film to the lower half of the outer layer glass, the optical efficiency was increased by 0.17 %. The energy output in the quasi-equilibrium state is 87 W, which is 8 W higher in the simulation. Water-vapor directly reaches the condensation section to reduce the formation of vortices under conditions where it absorbs sufficient energy to overcome its own gravity and ambient pressure, thus reducing heat loss and increasing thermal efficiency. Fig. 1. All-glass heat pipe vacuumed collector.
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•A metal heat pipe is replaced with glass to form an all-glass heat pipe evacuated collector tube.•Maximum thermal stress of 0.279 MPa is well below than the bearing range of 40–120 MPa.•All-glass structure fully copes with the transient local heating changes.•Optical efficiency is increased by 0.17% by the addition of the reflective film.•Yielding an energy output of 87 W in the quasi-thermal equilibrium state.
Metal heat pipe evacuated collector tube (ECT) suffer from cracks in the joint between the glass outer layer and the metal heat pipe due to the large difference in thermal expansion coefficients of glass and metal, resulting in non-industrialization. In this paper, the metal heat pipe is replaced with a glass heat pipe to form an all-glass heat pipe ECT to address the air-tight sealing problem, and a reflective film was added to the lower part of the outer tube to improve energy. According to these results, the thermal stress of 0.279 MPa is well below the bearing range of 40–120 MPa, and the maximum thermal strain of 0.175 mm/mm is also far less than the affordable value of 120 mm/mm, inducting the all-glass structure fully copes with the transient local heating changes. The optical efficiency is increased by 0.17 % by the addition of the reflective film, and yielding an energy output of 87 W and a maximum volume fraction of 4.8 % for liquid–water in the quasi-thermal equilibrium state. At the same time, the evaporation operating speed of the vapor can be increased by improving the solar radiation flux density and reducing thermal losses, and optimizing the multi-level and cross-scale vapor vortices can also improve the convective heat transfer rate, so they are future directions for development. However, there are the limitations of decreasing the thermal conductivity and increases the resistance due to the heat pipe conversion from metal to glass.
Succession of C-H activation and C-C activation was achieved by using a single rhodium(III) catalyst. Vinylcyclopropanes were used as versatile coupling partners. Mechanistic studies suggest that the ...olefin insertion step is rate-determining and a facile β-carbon elimination is involved, which represents a novel ring opening mode of vinylcyclopropanes.
An improved evacuated absorber tube (AT) design consisting of a semi-circular tube is proposed for large-aperture parabolic trough concentrator. The absorber tube also contains a flat-plate radiation ...shield in the vacuum part of the tube in the glass cover. To enhance the heat transfer in the AT, different fins geometries added to the bottom of the AT were analyzed here. Compared to an AT without fins, the thermal efficiency of the tube could be increased from 75.7% to 76.9% with a short and thick fin and to 77.3% with a long and thin fin in the flow velocity range of 0.4–1.5 m/s. The long and thin finned AT shows better enhancement of heat transfer, but the heat transfer performance factor also accounting for frictional losses is higher for short and thick fin. Simultaneously, increasing the number of long and thin fins in the AT would not improve much the heat transfer performance.
•The novel absorber tube (AT) consists of a semi-circular and a flat-plate radiation shield located in vacuum area.•Enhancement heat transfer adopts long and thin fins and short and thick fins.•Long and thin fins showed highest improvement of efficiency by 1.6%.•Short and thick fins had lowest pressure drop and heat transfer performance factor.
Studies investigating the changes in short-chain fatty acids (SCFAs) in patients with ulcerative colitis (UC) have yielded inconsistent results. We performed a meta-analysis of studies that ...investigated the alterations in different SCFAs among UC patients to assess their role in the development of UC.
Three databases were searched for relevant studies published as of April 2021. Results are presented as standardized mean difference (SMD) with 95% confidence interval (95% CI).
Eleven studies were included in the meta-analysis. Compared to healthy subjects, UC patients had significantly lower concentrations of total SCFAs (SMD = - 0.88, 95%CI - 1.44, - 0.33; P < 0.001), acetate (SMD = - 0.54, 95% CI - 0.91, - 0.17; P = 0.004), propionate, (SMD = - 0.37, 95% CI - 0.66, - 0.07; P = 0.016), and valerate (SMD = - 0.91, 95% CI - 1.45, - 0.38; P < 0.001). On subgroup analysis based on disease status, patients with active UC had reduced concentrations of acetate (SMD = - 1.83, 95% CI - 3.32, - 0.35; P = 0.015), propionate (SMD = - 2.51, 95% CI - 4.41, - 0.61; P = 0.009), and valerate (SMD = - 0.91, 95% CI - 1.45, - 0.38; P < 0.001), while UC patients in remission had similar concentrations with healthy subjects. Patients with active UC had lower butyrate level (SMD = - 2.09, 95% CI - 3.56, - 0.62; P = 0.005) while UC patients in remission had higher butyrate level (SMD = 0.71, 95% CI 0.33, 1.10; P < 0.001) compared with healthy subjects.
UC patients had significantly decreased concentrations of total SCFAs, acetate, propionate, and valerate compared with healthy subjects. In addition, inconsistent changes of certain special SCFAs were observed in UC patients with different disease status.
An improved absorber tube (AT) design consisting of a semi-circular and an external flat fin with a flat-plate radiation shield inside an evacuated annulus is proposed for large aperture parabolic ...trough concentrator (PTC) systems. In the present design, the AT’s semi-circular part absorbs the most sun rays. The other rays originally absorbed by the AT’s upper part is intercepted by the external two fins. The flat-plate radiation shield reflects the external radiation energy from the AT’s upper half back to the AT. The trough has an aperture of 8m and an 80° half rim angle. The AT consists of a semicircle with a diameter of 100 mm and outer fins. The optical and thermal efficiency of this new design was up to 83.3% and 80.3%, respectively. The optical and thermal efficiency was 8%-units higher than that of the traditional optimal design. The maximum temperature always appears at the edge of the fin, which is up to 50 °C higher than that of the heat transfer fluid (HTF) at 0.5 m/s, which was the optimal fluid rate for the new design. The fins also contribute to the efficiency of the PTC: 6.5% to the optical and over 3.5% to the thermal efficiency. The improved AT design will help to plan more effective PTC systems.
•New design approach for absorber tube in parabolic trough concentrator.•Absorber tube consists of a semi-circular and external fin with flat radiation shield inside evacuated annulus.•Optical and thermal efficiency of concentrator increased by 8%.
The relationship between conventional lipid parameters and arterial stiffness (AS) has been verified by previous studies. However, it remains unknown whether non‐conventional lipid parameters have ...certain predictive effect on AS represented by brachial‐ankle pulse wave velocity (baPWV). Therefore, the study was to explore the relationship between remnant cholesterol (RC) and other non‐conventional lipid parameters and AS in the general population free from cardiovascular disease. The study included 912 participants aged 24–84 years from a medical health checkup center of Murakami Memorial Hospital. Logistic regression analysis and receiver operating characteristic (ROC) curves were used to examine the association between non‐conventional lipid parameters and AS. The results showed that compared with non‐AS group, the AS group had higher RC, non‐high‐density lipoprotein cholesterol (Non‐HDL‐C), atherogenic index of plasma (AIP), lipoprotein combine index (LCI), atherosclerosis index (AI), triglycerides/HDL‐C (TG/HDL‐C), Castelli's risk index I (CRI‐I) and Castelli's risk index II (CRI‐II). Then, the authors divided participants into two groups by the optimal cutoff point of 23.6 of RC determined by Youden index. The baPWV was significantly higher in higher RC group compared with lower RC group, and RC was positively correlated with baPWV. Multivariate Logistic regression analysis showed that, regarding lower RC as reference, higher RC was independently associated with higher risk of AS, independent of other risk factors (OR = 1.794, 95% CI: 1.267‐2.539, p = .001). The area under the curve of AS predicted by RC was higher than that of other non‐conventional lipid parameters (almost all p < .05). The findings indicated that increased RC was a significant predictor of AS.
In this study, the efficiency of a large aperture 2-stage parabolic trough concentrator (PTC) is improved using an innovative design method for the secondary reflector (SR). The design method is ...based on an adaptive approach in which the SR is step-wise optimized to maximally reflect back to the absorber tube (AT) the part of solar radiation reflected by the primary reflector (PR) but not captured by the AT. The adaptive design method results in a SR design which consists of several parabolas with different focal lengths, each having a focus which lies in the focus of the PR. This ensures that the originally unabsorbed solar radiation will now hit the surface of AT. The optical efficiency of the PTC could be increased by 5.2% and thermal efficiency by 4.9%, respectively, compared to a case without optimized SR. In addition, the uniformity of the solar radiation flux on the AT’s outer wall could be doubled, its temperature was more even. The new adaptive design approach of the SR could help to better optimize PTC systems.
•New design approach for secondary mirror in parabolic trough concentrator.•Adaptive method to design secondary mirror.•Step-wise optimization to maximally reflect radiation to absorber.•Optical and thermal efficiency of concentrator increased by 5.2% and 4.9%.
Abstract
We present RISE (http://rise.zhanglab.net), a database of RNA Interactome from Sequencing Experiments. RNA-RNA interactions (RRIs) are essential for RNA regulation and function. RISE ...provides a comprehensive collection of RRIs that mainly come from recent transcriptome-wide sequencing-based experiments like PARIS, SPLASH, LIGR-seq, and MARIO, as well as targeted studies like RIA-seq, RAP-RNA and CLASH. It also includes interactions aggregated from other primary databases and publications. The RISE database currently contains 328,811 RNA-RNA interactions mainly in human, mouse and yeast. While most existing RNA databases mainly contain interactions of miRNA targeting, notably, more than half of the RRIs in RISE are among mRNA and long non-coding RNAs. We compared different RRI datasets in RISE and found limited overlaps in interactions resolved by different techniques and in different cell lines. It may suggest technology preference and also dynamic natures of RRIs. We also analyzed the basic features of the human and mouse RRI networks and found that they tend to be scale-free, small-world, hierarchical and modular. The analysis may nominate important RNAs or RRIs for further investigation. Finally, RISE provides a Circos plot and several table views for integrative visualization, with extensive molecular and functional annotations to facilitate exploration of biological functions for any RRI of interest.
The first total synthesis of an arcutine-type C20-diterpenoid alkaloid arcutinine has been achieved in both racemic and asymmetric forms. Construction of the C4 quaternary center and the pyrrolidine ...E ring in an early stage proved to be important for achieving the successful synthesis of the target alkaloid. Strategically, an asymmetric conjugate addition/aldol cascade and a decarboxylative allylation reaction allowed the establishment of the vicinal all-carbon quaternary stereocenters at C4 and C5. Furthermore, a sequence consisting of an intramolecular aza-Wacker cyclization, an oxidative dearomatization/intramolecular Diels–Alder cycloaddition cascade, and a ketyl-olefin cyclization enabled the assembly of the core structure and led to the total synthesis of arcutinine.
The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. ...This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may offer guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation.
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