Steam Condensation Cooled by Piezoelectric Driven Oscillating Air Flow

The piezoelectric (PE) fan is first put forward to use in the air-cooled condenser, and to enhance the exhaust steam condensation of large thermal power plants. The cooling performance of such a method is evaluated through numerical simulations. The study shows that the surface heat transfer coefficient with PE fan at the air side is higher than that of a conventional axial flow (AF) fan. While at the steam side of the tube, the surface heat transfer coefficient is also enhanced owing to the obvious fluctuation of liquid film caused by the vibration of the piezoelectric fan.Key words: Piezoelectric fan; Air-cooling condenser; Numerical simulation; Surface heat transfer coefficien

Sonochemical Degradation of Perfluorooctanesulfonate in Aqueous Film-Forming Foams

Aqueous film-forming foams (AFFFs) are fire extinguishing agents developed by the Navy to quickly and effectively combat fires occurring close to explosive materials and are utilized today at car races, airports, oil refineries, and military locations. Fluorochemical (FC) surfactants represent 1−5% of the AFFF composition, which impart properties such as high spreadability, negligible fuel diffusion, and thermal stability to the foam. FC’s are oxidatively recalcitrant, persistent in the environment, and have been detected in groundwater at AFFF training sites. Ultrasonic irradiation of aqueous FCs has been reported to degrade and subsequently mineralize the FC surfactants perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS). Here we present results of the sonochemical degradation of aqueous dilutions of FC-600, a mixture of hydrocarbon (HC) and fluorochemical components including cosolvents, anionic hydrocarbon surfactants, fluorinated amphiphilic surfactants, anionic fluorinated surfactants, and thickeners such as starch. The primary FC surfactant in FC-600, PFOS, was sonolytically degraded over a range of FC-600 aqueous dilutions, 65 ppb < [PFOS]_i < 13100 ppb. Sonochemical PFOS−AFFF decomposition rates, R_(AFFF)^(−PFOS), are similar to PFOS−Milli-Q rates, R_(MQ)^(−PFOS), indicating that the AFFF matrix only had a minor effect on the sonochemical degradation rate, 0.5 < R_(AFFF)^(−PFOS)/R_(MQ)^(−PFOS) < 2.0, even though the total organic concentration was 50 times the PFOS concentration, [Org]_(tot)/[PFOS] ~50, consistent with the superior FC surfactant properties. Sonochemical sulfate production is quantitative, Δ[SO_4^(2−)]/Δ[PFOS] ≥ 1, indicating that bubble-water interfacial pyrolytic cleavage of the C−S bond in PFOS is the initial degradation step, in agreement with previous studies done in Milli-Q water. Sonochemical fluoride production is significantly below quantitative expectations, Δ[F^−]/Δ[PFOS] ~4 vs 17, suggesting that in the AFFF matrix, PFOS’ fluorochemical tail is not completely degraded, whereas Milli-Q studies yielded quantitative F− production. Measurements of time-dependent methylene blue active substances and total organic carbon indicate that the other FC-600 components were also sonolytically decomposed

Magic angle in thermal conductivity of twisted bilayer graphene

We report a local minimum in thermal conductivity in twisted bilayer graphene (TBG) at the angle of 1.08$^\circ$, which corresponds to the 'magic angle' in the transition of several other reported properties. Within the supercell of a moir\'e lattice, different stacking modes generate phonon scattering sites which reduce the thermal conductivity of TBG. The thermal magic angle arises from the competition between the delocalization of atomic vibrational amplitudes and stresses on one hand, and the increased AA stacking density on the other hand. The former effect weakens the scattering strength of a single scatterer while the latter one increases the density of scatterers. The combination of these two effects eventually leads to the apparition of the highlighted irregularity in heat conduction. The manifestation of a magic angle, disclosing new thermal mechanisms at nanoscale, further uncovers the unique physics of two-dimensional materials.Comment: 15 pages, 5 figure

Phylogenetic Relationships in the Festuca-Lolium Complex (Loliinae; Poaceae): New Insights from Chloroplast Sequences

The species within the Lolium/Festuca grass complex have dispersed and colonized large areas of temperate global grasslands both naturally and by human intervention. The species within this grass complex represent some of the most important grass species both for amenity and agricultural use worldwide. There has been renewed interest by grass breeders in producing hybrid combinations between these species and several countries now market Festulolium varieties as a combination of genes from both genera. The two genera have been differentiated by their inflorescence structure, but controversy has surrounded the taxonomic classification of the Lolium-Festuca complex species for several decades. In order to better understand the complexities within the Lolium/Festuca complex and their genetic background, the phylogeny of important examplers from the Lolium-Festuca complex were reconstructed. In total 40 taxa representing the Festuca and Lolium species with Vulpia myuros and Brachypodium distachyon as outgroups were sampled, using two noncoding intergenic spacers (trnQ-rps16, trnH-psbA) and one coding gene (rbcL). Maximum parsimony (MP), Bayesian inference (BI) analyses based on each partition and combined plastid DNA dataset, and median-jointing network analysis were employed. The outcomes strongly suggested that the subgen. Schedonorus has a close relationship to Lolium, and it is also proposed to move the sect. Leucopoa from subgen. Leucopoa to Subgen. Schedonorus and to separate sect. Breviaristatae from the subgen. Leucopoa. We found that F. californica could be a lineage of hybrid origin because of its intermediate placement between the broad-leaved and fine-leaved clade

Geochemistry and geochronology of dolerite dykes from the Daba and Dongbo peridotite massifs, SW Tibet: Insights into the style of mantle melting at the onset of Neo-Tethyan subduction

This study reports compositional and whole-rock Sr-Nd isotope data as well as zircon U-Pb geochronological data on dolerite dikes from the Daba and Dongbo ultramafic massifs, southwest Yarlung-Zangbo Suture Zone (YZSZ), Tibet. The 120.6 \ub1 1.6 Ma dolerite dikes from the Daba peridotite exhibit normal mid-ocean ridge basalt (N-MORB)-type normalized mutli-element patterns [(La/Yb)N = 0.43-0.72] with noticeable negative Nb and Th anomalies. They have high initial 87Sr/8624 Sr ratios (87Sr/8625 Sr(i) = 0.70720-0.70788) and high \u3b5Nd(t) values (+7.4 to +7.9). The 125.4 \ub1 1.8 Ma dolerite intrusions within the Dongbo peridotite show N-MORB\u2012type trace element profiles [(La/Yb)N = 0.65-0.84] characterized by apparent negative anomalies in Nb and Th, and mild negative anomalies in Ti (\ub1 Y). They also have high 87Sr/8629 Sr(i) ratios (0.70611-0.70679) and elevated \u3b5Nd(t) values (+7.8 to +8.2). Semi-quantitative La/Yb vs. Dy/Yb modeling demonstrates that the parental magmas of the investigated dolerite dikes derived from more than 20% (cumulative) melting of a (broad) mantle source region that had a spinel-bearing N-MORB\u2013like lherzolitic composition. Our geochemical and isotopic data indicate that the composition of the inferred mantle source was influenced by minor input of subducted crustal material. The petrogenesis of the Daba and Dongbo massifs could be linked to upwelling of an asthenospheric source that caused continental rift and subsequent seafloor spreading, followed by subduction initiation adjacent to a passive margin during the early Cretaceous (~130-120 Ma). Our study provides a more detailed, and perhaps more elegant, hypothesis for the tectono-magmatic evolution of the southwestern YZSZ "ophiolitic" peridotites after their accretion beneath a Neo-Tethyan marginal basin

A Chinese cave links climate change, social impacts, and human adaptation over the last 500 years.

The collapse of some pre-historical and historical cultures, including Chinese dynasties were presumably linked to widespread droughts, on the basis of synchronicities of societal crises and proxy-based climate events. Here, we present a comparison of ancient inscriptions in Dayu Cave from Qinling Mountains, central China, which described accurate times and detailed impacts of seven drought events during the period of 1520-1920 CE, with high-resolution speleothem records from the same cave. The comparable results provide unique and robust tests on relationships among speleothem δ(18)O changes, drought events, and societal unrest. With direct historical evidences, our results suggest that droughts and even modest events interrupting otherwise wet intervals can cause serious social crises. Modeling results of speleothem δ(18)O series suggest that future precipitation in central China may be below the average of the past 500 years. As Qinling Mountain is the main recharge area of two large water transfer projects and habitats of many endangered species, it is imperative to explore an adaptive strategy for the decline in precipitation and/or drought events.We gratefully acknowledge the NBRPC (2013CB955902), NSFC (41372192; 41290254; 41230524; 41023006), and the WLF-CAS for funding this research. This study was also partially supported by Taiwan MOST (103-2119-M-002-022) and NTU (101R7625) grants. H.C. and R.L.E. received financial support from the U.S. NSF (EAR-0908792 and EAR-1211299), and S.F.M.B. received support from the Swiss NSF (CRSI22_132646/1).This is the final version. It was first published by NPG at http://www.nature.com/srep/2015/150717/srep12284/full/srep12284.html#author-information

A Chinese cave links climate change, social impacts, and human adaptation over the last 500 years

The collapse of some pre-historical and historical cultures, including Chinese dynasties were presumably linked to widespread droughts, on the basis of synchronicities of societal crises and proxy-based climate events. Here, we present a comparison of ancient inscriptions in Dayu Cave from Qinling Mountains, central China, which described accurate times and detailed impacts of seven drought events during the period of 1520–1920 CE, with high-resolution speleothem records from the same cave. The comparable results provide unique and robust tests on relationships among speleothem δ18O changes, drought events, and societal unrest. With direct historical evidences, our results suggest that droughts and even modest events interrupting otherwise wet intervals can cause serious social crises. Modeling results of speleothem δ18O series suggest that future precipitation in central China may be below the average of the past 500 years. As Qinling Mountain is the main recharge area of two large water transfer projects and habitats of many endangered species, it is imperative to explore an adaptive strategy for the decline in precipitation and/or drought events

Clinical Implications of Unmasking Dormant Conduction After Circumferential Pulmonary Vein Isolation in Atrial Fibrillation Using Adenosine: A Systematic Review and Meta-Analysis

Purpose: Circumferential pulmonary vein isolation (CPVI) is a routine ablation strategy of atrial fibrillation (AF). The adenosine test can be used to unmask dormant conduction (DC) of pulmonary veins after CPVI, thereby demonstrating possible pulmonary vein re-connection and the need for further ablation. However, whether adenosine test could help improve the long term successful rate of CPVI is still controversial. This systemic review and meta-analysis was to determine the clinical utility of the adenosine test.Methods: PubMed, EMBASE, Web of Science and Cochrane Library database were searched through July 2016 to identify relevant studies using the keywords “dormant pulmonary vein conduction,” “adenosine test,” “circumferential pulmonary vein isolation,” and “atrial fibrillation.” A random-effects model was used to compare pooled outcomes and tested for heterogeneity.Results: A total of 17 studies including 5,169 participants were included in the final meta-analysis. Two groups of comparisons were classified: (1) Long-term successful rate in those AF patients underwent CPVI with and without adenosine test [Group A (+) and Group A (−)]; (2) Long-term successful rate in those patients who had adenosine test with and without dormant conduction [Group DC (+) and Group DC (−)]. The overall meta-analysis showed that no significant difference can be observed between Group A (+) and Group A (−) (RR 1.08; 95% CI 0.97–1.19; P = 0.16; I2 = 66%) and between Group DC (+) and Group DC (−) (RR 1.01; 95% CI 0.91–1.12; P = 0.88; I2 = 60%).Conclusion: Pooled meta-analysis suggested adenosine test may not improve long-term successful rate in AF patients underwent CPVI. Furthermore, AF recurrence may not be decreased by eliminating DC provoked by adenosine, even though adenosine test was applied after CPVI