| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Hu, Jinhong, et al.
(författare)
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Safety and immunogenicity of a malaria vaccine, Plasmodium falciparum AMA-1/MSP-1 chimeric protein formulated in montanide ISA 720 in healthy adults
- 2008
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Ingår i: PLOS ONE. - : PLOS. - 1932-6203. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The P. falciparum chimeric protein 2.9 (PfCP-2.9) consisting of the sequences of MSP1-19 and AMA-1 (III) is a malaria vaccine candidate that was found to induce inhibitory antibodies in rabbits and monkeys. This was a phase I randomized, single-blind, placebo-controlled, dose-escalation study to evaluate the safety and immunogenicity of the PfCP-2.9 formulated with a novel adjuvant Montanide ISA720. Fifty-two subjects were randomly assigned to 4 dose groups of 10 participants, each receiving the test vaccine of 20, 50, 100, or 200 microg respectively, and 1 placebo group of 12 participants receiving the adjuvant only.METHODS AND FINDINGS: The vaccine formulation was shown to be safe and well-tolerated, and none of the participants withdrew. The total incidence of local adverse events (AEs) was 75%, distributed among 58% of the placebo group and 80% of those vaccinated. Among the vaccinated, 65% had events that were mild and 15% experienced moderate AEs. Almost all systemic adverse reactions observed in this study were graded as mild and required no therapy. The participants receiving the test vaccine developed detectable antibody responses which were boosted by the repeated vaccinations. Sixty percent of the vaccinated participants had high ELISA titers (>1:10,000) of antigen-specific antibodies which could also recognize native parasite proteins in an immunofluorescence assay (IFA).CONCLUSION: This study is the first clinical trial for this candidate and builds on previous investigations supporting PfCP-2.9/ISA720 as a promising blood-stage malaria vaccine. Results demonstrate safety, tolerability (particularly at the lower doses tested) and immunogenicity of the formulation. Further clinical development is ongoing to explore optimizing the dose and schedule of the formulation to decrease reactogenicity without compromising immunogenicity.TRIAL REGISTRATION: Chinese State Food and Drug Administration (SFDA) 2002SL0046; Controlled-Trials.com ISRCTN66850051 [66850051].
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| 7. |
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| 8. |
- Abdoullaye, Doukary, et al.
(författare)
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Permanent genetic resources added to molecular ecology resources database 1 August 2009 - 30 September 2009
- 2010
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Ingår i: Molecular Ecology Resources. - : Wiley. - 1755-098X .- 1755-0998. ; 10:1, s. 232-236
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Tidskriftsartikel (refereegranskat)abstract
- This article documents the addition of 238 microsatellite marker loci and 72 pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Adelges tsugae, Artemisia tridentata, Astroides calycularis, Azorella selago, Botryllus schlosseri, Botrylloides violaceus, Cardiocrinum cordatum var. glehnii, Campylopterus curvipennis, Colocasia esculenta, Cynomys ludovicianus, Cynomys leucurus, Cynomys gunnisoni, Epinephelus coioides, Eunicella singularis, Gammarus pulex, Homoeosoma nebulella, Hyla squirella, Lateolabrax japonicus, Mastomys erythroleucus, Pararge aegeria, Pardosa sierra, Phoenicopterus ruber ruber and Silene latifolia. These loci were cross-tested on the following species: Adelges abietis, Adelges cooleyi, Adelges piceae, Pineus pini, Pineus strobi, Tubastrea micrantha, three other Tubastrea species, Botrylloides fuscus, Botrylloides simodensis, Campylopterus hemileucurus, Campylopterus rufus, Campylopterus largipennis, Campylopterus villaviscensio, Phaethornis longuemareus, Florisuga mellivora, Lampornis amethystinus, Amazilia cyanocephala, Archilochus colubris, Epinephelus lanceolatus, Epinephelus fuscoguttatus, Symbiodinium temperate-A clade, Gammarus fossarum, Gammarus roeselii, Dikerogammarus villosus and Limnomysis benedeni. This article also documents the addition of 72 sequencing primer pairs and 52 allele specific primers for Neophocaena phocaenoides.
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| 9. |
- Blunden, Jessica, et al.
(författare)
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State of the Climate in 2012
- 2013
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Ingår i: Bulletin of The American Meteorological Society - (BAMS). - 0003-0007 .- 1520-0477. ; 94:8, s. S1-S258
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Tidskriftsartikel (refereegranskat)abstract
- For the first time in serveral years, the El Nino-Southern Oscillation did not dominate regional climate conditions around the globe. A weak La Ni a dissipated to ENSOneutral conditions by spring, and while El Nino appeared to be emerging during summer, this phase never fully developed as sea surface temperatures in the eastern conditions. Nevertheless, other large-scale climate patterns and extreme weather events impacted various regions during the year. A negative phase of the Arctic Oscillation from mid-January to early February contributed to frigid conditions in parts of northern Africa, eastern Europe, and western Asia. A lack of rain during the 2012 wet season led to the worst drought in at least the past three decades for northeastern Brazil. Central North America also experienced one of its most severe droughts on record. The Caribbean observed a very wet dry season and it was the Sahel's wettest rainy season in 50 years. Overall, the 2012 average temperature across global land and ocean surfaces ranked among the 10 warmest years on record. The global land surface temperature alone was also among the 10 warmest on record. In the upper atmosphere, the average stratospheric temperature was record or near-record cold, depending on the dataset. After a 30-year warming trend from 1970 to 1999 for global sea surface temperatures, the period 2000-12 had little further trend. This may be linked to the prevalence of La Ni a-like conditions during the 21st century. Heat content in the upper 700 m of the ocean remained near record high levels in 2012. Net increases from 2011 to 2012 were observed at 700-m to 2000-m depth and even in the abyssal ocean below. Following sharp decreases in to the effects of La Ni a, sea levels rebounded to reach records highs in 2012. The increased hydrological cycle seen in recent years continued, with more evaporation in drier locations and more precipitation in rainy areas. In a pattern that has held since 2004, salty areas of the ocean surfaces and subsurfaces were anomalously salty on average, while fresher areas were anomalously fresh. Global tropical cyclone activity during 2012 was near average, with a total of 84 storms compared with the 1981-2010 average of 89. Similar to 2010 and 2011, the North Atlantic was the only hurricane basin that experienced above-normal activity. In this basin, Sandy brought devastation to Cuba and parts of the eastern North American seaboard. All other basins experienced either near-or below-normal tropical cyclone activity. Only three tropical cyclones reached Category 5 intensity-all in Bopha became the only storm in the historical record to produce winds greater than 130 kt south of 7 N. It was also the costliest storm to affect the Philippines and killed more than 1000 residents. Minimum Arctic sea ice extent in September and Northern Hemisphere snow cover extent in June both reached new record lows. June snow cover extent is now declining at a faster rate (-17.6% per decade) than September sea ice extent (-13.0% per decade). Permafrost temperatures reached record high values in northernmost Alaska. A new melt extent record occurred on 11-12 July on the Greenland ice sheet; 97% of the ice sheet showed some form of melt, four times greater than the average melt for this time of year. The climate in Antarctica was relatively stable overall. The largest maximum sea ice extent since records begain in 1978 was observed in September 2012. In the stratosphere, warm air led to the second smallest ozone hole in the past two decades. Even so, the springtime ozone layer above Antarctica likely will not return to its early 1980s state until about 2060. Following a slight decline associated with the global 2 emissions from fossil fuel combustion and cement production reached a record 9.5 +/- 0.5 Pg C in 2011 and a new record of 9.7 +/- 0.5 Pg C is estimated for 2012. Atmospheric CO2 concentrations increased by 2.1 ppm in 2012, to 392.6 ppm. In spring 2012, 2 concentration exceeded 400 ppm at 7 of the 13 Arctic observation sites. Globally, other greenhouse gases including methane and nitrous oxide also continued to rise in concentration and the combined effect now represents a 32% increase in radiative forcing over a 1990 baseline. Concentrations of most ozone depleting substances continued to fall.
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| 10. |
- Cao, Huiming, et al.
(författare)
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Effect of Enterohepatic Circulation on the Accumulation of Per- and Polyfluoroalkyl Substances : Evidence from Experimental and Computational Studies
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:5, s. 3214-3224
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Tidskriftsartikel (refereegranskat)abstract
- The pharmacokinetic characteristics of per- and polyfluoroalkyl substances (PFAS) affect their distribution and bioaccumulation in biological systems. The enterohepatic circulation leads to reabsorption of certain chemicals from bile back into blood and the liver and thus influences their elimination, yet its influence on PFAS bioaccumulation remains unclear. We explored the role of enterohepatic circulation in PFAS bioaccumulation by examining tissue distribution of various PFAS in wild fish and a rat model. Computational models were used to determine the reabsorbed fractions of PFAS by calculating binding affinities of PFAS for key transporter proteins of enterohepatic circulation. The results indicated that higher concentrations were observed in blood, the liver, and bile compared to other tissues for some PFAS in fish. Furthermore, exposure to a PFAS mixture on the rat model showed that the reabsorption phenomenon appeared during 8-12 h for most long-chain PFAS. Molecular docking calculations suggest that PFAS can bind to key transporter proteins via electrostatic and hydrophobic interactions. Further regression analysis adds support to the hypothesis that binding affinity of the apical sodium-dependent bile acid transporter is the most important variable to predict the human half-lives of PFAS. This study demonstrated the critical role of enterohepatic circulation in reabsorption, distribution, and accumulation of PFAS.
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| 11. |
- Cao, Huiming, et al.
(författare)
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Screening of Potential PFOS Alternatives To Decrease Liver Bioaccumulation : Experimental and Computational Approaches
- 2019
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:5, s. 2811-2819
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Tidskriftsartikel (refereegranskat)abstract
- Perfluorooctanesulfonate (PFOS) is a persistent organic pollutant with significant bioaccumulation potential in liver tissues. Exposure to PFOS could cause increase of liver weight, induce adenomas of the liver, and cause hepatomegaly. Alternatives of PFOS might be designed and synthesized that have significantly lower liver bioaccumulation. In this study, we conducted animal exposure experiments to investigate tissue accumulations of 14 per- and polyfluoroalkyl substances. Correlation analysis demonstrated that accumulation of the compounds in rat liver had strong correlations with their binding affinities of liver fatty acid binding protein (LFABP). Thus, we combined a quantitative structure-activity relationship model with molecular dynamics (MD) simulations to develop computational models to predict the LFABP binding affinities of two newly synthesized alternatives, perfluorodecalin-2-sulfonic acid and N-diperfluorobutanoic acid. The binding characteristics of the PFOS alternatives for LFABP were elaborated to explore how the different structural modifications of molecules influenced the underlying binding mechanisms. Subsequent animal experiments demonstrated that the binding free energy calculations based on the MD simulations provided a good indicator to reflect the relative degree of liver accumulation of the PFOS alternatives in the same exposure doses and durations. Our findings from the combination of experimental exposure and computational model can provide helpful information to design potential alternatives of PFOS with weak LFABP binding capability and low liver accumulation.
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| 12. |
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| 13. |
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| 14. |
- Cao, Zhen, et al.
(författare)
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An analysis of pool boiling heat transfer on nanoparticle-coated surfaces
- 2019
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 159, s. 5880-5887
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, copper surfaces were deposited with Cu-Zinc nanoparticles of 0.6 mg by an electrophoretic deposition method (EPD). Two deposition patterns were designed, i.e., fully deposition (EPD-F) and channel-pattern deposition (EPD-C). In the channel-pattern deposition, the smooth channel and the deposition channel occur alternatively, by keeping the width of the smooth channel as 3 mm, but the width of the deposition channel as 1 mm (EPD-C1) and 3 mm (EPD-C2), respectively. Pool boiling of HFE-7200 was studied on a smooth surface and the nanoparticle-coating surfaces. The results showed that the surface with fully deposition (EPD-F) had the highest heat transfer coefficient, around 100% enhancement compared with the smooth surface, while the surface with channel-pattern deposition (EPD-C2) had the highest critical heat flux, around 33.3% enhancement in comparison to the smooth surface. A high speed camera was used to study bubble dynamics, which indicated that the nanoparticle-coating surfaces had smaller bubble departure diameters and higher departure frequencies. A heat transfer model, considering natural convection, re-formation of thermal boundary layer and microlayer evaporation, was formulated to predict the heat transfer on the test surfaces, showing good prediction at low and moderate heat fluxes. CHF was analyzed from the perspective of the Rayleigh-Taylor instability.
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| 15. |
- Cao, Zhen, et al.
(författare)
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AN EXPERIMENTAL STUDY ON HEAT TRANSFER PERFORMANCE OF JET IMPINGEMENT ARRAYS
- 2022
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Ingår i: Proceedings of ASME 2022 Heat Transfer Summer Conference, HT 2022. - 9780791885796
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Konferensbidrag (refereegranskat)abstract
- Jet impingement cooling is an effective way for thermal management in electronics, prevailed over many other single heat transfer modes. In general, jet arrays are better than a single jet, enhancing jet cooling performance. However, the performance of jet arrays is strongly dependent on the jet configurations, e.g., adjacent jet interval and hole-to-surface distance. Thus, in this study, jet impingement cooling is investigated on a flat heating surface placed in a channel, including in-line double jet cooling, in-line three jet cooling, and in-line four jet cooling. It is known that the outlet configuration could influence the jet performance because of the cross flow effect, and herein the outlet is designed to have intermediate cross flow only. The local Nusselt number distribution is experimentally measured by the liquid crystal method. Then the effect of the adjacent jet interval on the jet cooling performance on the target surface is compared. It is found that the jet array indeed enhances heat transfer. For example, based on the results, it is seen that in comparison to cross flow cooling, the average Nusselt number is improved by 34% by the in-line double jet cooling, and correspondingly the maximum Nusselt number is enhanced by 51%.
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| 16. |
- Cao, Zhen, et al.
(författare)
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Bubble dynamics and mechanistic boiling heat transfer prediction on a scored copper surface
- 2021
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2116
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Konferensbidrag (refereegranskat)abstract
- In this study, pool boiling heat transfer of de-ionized water was experimentally studied on a scored copper surface at a heat-flux range of 0 - 60 W/cm2. Bubble dynamics in an isolated bubble region were carefully investigated, including bubble departure diameters, bubble departure frequencies, and active nucleation site densities. The bubble dynamics were compared with available models, indicating the suitable models regarding the present experimental results. Then, based on the bubble dynamics, a mechanistic heat transfer model, developed in our previous studies, was employed to predict the present boiling curve. In the mechanistic model, heat fluxes from natural convection, transient heat conduction, and microlayer evaporation were incorporated.
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| 17. |
- Cao, Zhen, et al.
(författare)
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Coating engineering for boiling heat transfer toward immersion cooling
- 2021
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Ingår i: Advances in Heat Transfer. - : Elsevier. - 0065-2717.
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Bokkapitel (refereegranskat)abstract
- With the technological advancements in electronics, thermal management is becoming a concern that considerably affects the performance of electronic parts and systems, and two-phase immersion cooling is attracting attention due to its preferable cooling capacity. In immersion cooling, heat is dissipated by boiling that occurs on hot surfaces immersed in coolants. Therefore, it is essential to investigate boiling towards the realization and optimization of immersion cooling. Extensive studies have been carried out in terms of boiling heat transfer, e.g., bubble dynamics, heat transfer mechanisms, and critical heat flux, which convincingly indicate that boiling heat transfer greatly depends on surface characteristics and liquid properties as well as interactions between surfaces and liquids. As a consequence, many technologies have been applied to tailor-made or engineered surfaces to achieve an enhancement in boiling. Accordingly, this chapter will concentrate on technologies that produce thin film coatings on target surfaces, like CPU and memories in electronics, enabling high-efficient boiling performance and having good compatibility with electronics. Specifically, the chapter will be organized mainly with the following sections: introduction, fundamentals of boiling, coating technologies for boiling enhancement, and exploration of the enhancement mechanism. Through this work, it is expected to provide general insights into boiling heat transfer and give suggestions regarding the future directions of boiling heat transfer research.
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| 18. |
- Cao, Zhen, et al.
(författare)
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Dimensionless analysis on liquid-liquid flow patterns and scaling law on slug hydrodynamics in cross-junction microchannels
- 2018
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 344, s. 604-615
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Tidskriftsartikel (refereegranskat)abstract
- Liquid-liquid flow patterns and slug hydrodynamics were experimentally studied in non-circular glass microchannels with water-butanol, water-toluene, water–oil and water-hexane systems, considering various hydraulic diameters (600 µm, 400 µm, 200 µm), inlet junctions (crossed, T) and aspect ratios (0.5, 1). The aqueous phase was the continuous phase due to the hydrophilic microchannel walls and the organic phase was the dispersed phase. Three main flow patterns were observed, i.e., annular flow, slug flow and droplet flow. The mechanism of flow pattern formation was explained by a force analysis, based on which, a dimensionless analysis regarding Weber number and Reynolds number was performed to develop general flow pattern transition criteria. Additionally, slug velocities and slug length were investigated. A new scaling law was proposed to predict the slug length and it showed a good agreement with the experimental results. A linear relationship between the slug velocity and the bulk velocity of the two phases was obtained.
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| 19. |
- Cao, Zhen, et al.
(författare)
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Electrophoretic deposition surfaces to enhance HFE-7200 pool boiling heat transfer and critical heat flux
- 2019
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 146
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Tidskriftsartikel (refereegranskat)abstract
- Modulated nanoparticle-coating surfaces were fabricated by an improved electrophoretic deposition technique in this study. Pool boiling experiments were studied for HFE-7200 on the modulated nanoparticle-coating surfaces, with a smooth surface and uniform coating surfaces as comparison. It was found that the present modulated coating surfaces can enhance the heat transfer coefficient and the critical heat flux by 60% and 20%–40%, respectively, in comparison to the smooth surface, while the uniform coating surface can improve heat transfer coefficients by maximum 100%, but cannot enhance critical heat fluxes. Heat transfer on the modulated nanoparticle-coating surfaces was theoretically analyzed by a mechanistic model which considered free convection, transient conduction and microlayer evaporation. The heat transfer can be predicted by the model, especially at low-to-moderate heat fluxes. Additionally, referring to the bubble visualization at critical heat fluxes, possible mechanisms to trigger critical heat fluxes were discussed. Afterwards, a critical heat flux model originating from the Zuber hydrodynamic instability model, was employed to predict the experimental results, showing a good prediction ability.
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| 20. |
- Cao, Zhen, et al.
(författare)
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Enhancement of HFE-7200 pool boiling heat transfer on copper surfaces with nanoparticle coatings
- 2018
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Ingår i: Proceeding: International Heat Transfer Conference 16. - 2377-424X. ; , s. 1341-1347
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Konferensbidrag (refereegranskat)abstract
- Saturated pool boiling heat transfer of HFE-7200 is investigated experimentally on copper surfaces with nanoparticle coatings at atmospheric pressure. The coatings are generated by an electrophoretic deposition method. Two modified surfaces are prepared with Cu-Zinc nanoparticles of 0.3 mg and 0.6 mg, respectively. During the deposition, ethanol works as the solvent while the electrical potential and deposition time are controlled as 9.5 V and 30 min, respectively. The experimental results show heat transfer is considerably enhanced by the nanoparticle coatings. The surface with 0.6 mg nanoparticles (EDS-2) performs better than the surface with 0.3 mg nanoparticles (EDS-1), and a maximum 140% heat transfer enhancement is achieved on the surface EDS-2 compared with the SS. However, the critical heat flux is not enhanced by the coatings but even slightly decreased. A high speed visualization is employed to capture bubble behavior. It is found that bubbles on EDS-1 and EDS-2 have smaller sizes and higher departure frequency than those on the SS before reaching the critical heat flux. However, at critical heat fluxes, a vapor blanket appears on all surfaces.
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| 21. |
- Cao, Zhen, et al.
(författare)
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Enhancement of HFE-7200 pool boiling heat transfer on copper surfaces with nanoparticle coatings
- 2018
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Ingår i: International Heat Transfer Conference 16. - Connecticut : Begell House. - 9781567004748 - 9781567004731 ; , s. -1347
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Konferensbidrag (refereegranskat)abstract
- Saturated pool boiling heat transfer of HFE-7200 is investigated experimentally on copper surfaces with nanoparticle coatings at atmospheric pressure. The coatings are generated by an electrophoretic deposition method. Two modified surfaces are prepared with Cu-Zinc nanoparticles of 0.3 mg and 0.6 mg, respectively. During the deposition, ethanol works as the solvent while the electrical potential and deposition time are controlled as 9.5 V and 30 min, respectively. The experimental results show heat transfer is considerably enhanced by the nanoparticle coatings. The surface with 0.6 mg nanoparticles (EDS-2) performs better than the surface with 0.3 mg nanoparticles (EDS-1), and a maximum 140% heat transfer enhancement is achieved on the surface EDS-2 compared with the SS. However, the critical heat flux is not enhanced by the coatings but even slightly decreased. A high speed visualization is employed to capture bubble behavior. It is found that bubbles on EDS-1 and EDS-2 have smaller sizes and higher departure frequency than those on the SS before reaching the critical heat flux. However, at critical heat fluxes, a vapor blanket appears on all surfaces.
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| 22. |
- Cao, Zhen, et al.
(författare)
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Heat transfer prediction and critical heat flux mechanism for pool boiling of NOVEC-649 on microporous copper surfaces
- 2019
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 141, s. 818-834
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Tidskriftsartikel (refereegranskat)abstract
- Pool boiling performance of NOVEC-649 was experimentally studied on microporous surfaces prepared by an electrochemical deposition method. Microporous structures contribute to large surface roughness values and provide large quantities of cavities ranging from several hundreds of nanometers to several microns for bubble nucleation. The results show that a maximum enhancement of 600% in heat transfer coefficient and a maximum enhancement of 55% in critical heat flux are achieved on the deposited surfaces, compared with a smooth copper surface. Experimental heat transfer coefficients were compared with literature correlations, considering the effects of roughness and surface-liquid combination. Then a fitted Rohsenow correlation was discussed and developed to predict the present results. Experimental critical heat fluxes were compared with classical models. It was found that the critical heat flux on the smooth surface could be predicted by the lift-off model and the Kandlikar model, but these models cannot predict the critical heat fluxes on the deposited surfaces well. Following, the Kandlikar model was modified by further considering a wicking force and a roughness-factor-dependent surface tension force. The present modified CHF model was validated by comparing with present experimental data and the literature, with a deviation around ±30%.
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| 23. |
- Cao, Zhen, et al.
(författare)
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Liquid-liquid flow patterns in microchannels
- 2017
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Ingår i: Heat Transfer Equipment; Heat Transfer in Multiphase Systems; Heat Transfer Under Extreme Conditions; Nanoscale Transport Phenomena; Theory and Fundamental Research in Heat Transfer; Thermophysical Properties; Transport Phenomena in Materials Processing and Manufacturing. - 9780791857892 ; 2
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Konferensbidrag (refereegranskat)abstract
- In the present work, liquid-liquid flow patterns positioned 40 mm downstream the inlet of microchannels were experimentally investigated, including the effect of hydraulic diameter (Dh), liquid properties, aspect ratio of cross section (a) and inlet configuration. Deionized water, butanol, toluene and hexane were selected as probe fluids with water as the continuous phase. Cross-inlet microchannels of 200 μm ∗ 200 μm (Dh = 200 μm), 400 μm ∗ 400 μm (Dh = 400 μm), 600 μm ∗ 600 μm (Dh = 600 μm) and 600 μm ∗ 300 μm (Dh = 400 μm) as well as a T-inlet microchannel of 600 μm ∗ 300 μm (Dh = 400 μm) were tested. For the tests in the microchannels of Dh = 600 μm and 400 μm, the superficial velocities of the dispersed phase and continuous phase varied between 0.3 mm/s and 12 mm/s and between 0.2 mm/s and 50 mm/s, while in the microchannel of Dh = 200 μm the superficial velocities of the dispersed phase and continuous phase ranged from 0.3 mm/s to 21 mm/s and from 0.2 mm/s to 150 mm/s. Annular flow, deformed interface flow, slug flow, intermittent flow, droplet and slug train flow and droplet flow were detected in the experiment. It shows that flow patterns depend on the hydraulic diameter, liquid properties, inlet configuration and aspect ratio significantly. Dimensionless analysis was employed to develop universal flow pattern maps regardless of the hydraulic diameter and liquid properties. It is indicated that an acceptable universal flow pattern map was derived based on the redefined dimensionless number Rei 0.2 ∗Wei 0.4, especially for the boundaries of the slug-droplet transitions, which are independent on the hydraulic diameter to some extent. The other dimensionless number Wei∗Ohi worked rather effectively to develop a universal flow pattern map independent on liquid properties. The boundaries of the flow pattern transitions in different liquid-liquid flow almost overlap with each other.
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| 24. |
- Cao, Zhen, et al.
(författare)
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Model-based assessment of boiling heat transfer enhanced by coatings
- 2022
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 196
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Tidskriftsartikel (refereegranskat)abstract
- The present study aims to investigate boiling heat transfer enhancement on coated surfaces, based on mechanistic models. An electrochemical deposition method was used to fabricate coatings on copper surfaces which enhance critical heat flux and heat transfer coefficient of deionized water by 35.5% and 40.1%, respectively, compared with a smooth surface. Bubble dynamics indicates that regardless of surfaces, scaling laws of Db*∝t*0.5 and Db*∝t*0.2 are followed in the inertia-controlled growth stage and the heat-diffusion-controlled growth stage, respectively, concerning normalized bubble diameter (Db*) and normalized bubble time (t*). The coating decreases the bubble departure diameter to one-third to half of that on the smooth surface and increases the departure frequency to three times that on the smooth surface. In addition, the coated surface provides more active nucleation sites which are 1, 2 order magnitude higher than the smooth surface. With these insights, a mechanistic heat transfer model was established by quantifying natural convection, transient heat conduction, and microlayer evaporation, which matches well with the measured pool boiling curve. In the end, critical heat flux was explored experimentally and theoretically. Inspired by the coalesced bubble behavior at high heat flux and the Kandlikar force model, a new force-balance model was proposed by incorporating a surface-dependent surface tension force and adding a new capillary wicking force. The present model presents a better prediction of critical heat flux, verified by the current measurement and the literature.
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| 25. |
- Cao, Zhen, et al.
(författare)
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Nanoparticle-Assisted Pool Boiling Heat Transfer on Micro-Pin-Fin Surfaces
- 2021
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:3, s. 1089-1101
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Tidskriftsartikel (refereegranskat)abstract
- Boiling heat transfer intensification is of significant relevance to energy conversion and various cooling processes. This study aimed to enhance the saturated pool boiling of FC-72 (a dielectric liquid) by surface modifications and explore mechanisms of the enhancement. Specifically, circular and square micro pin fins were fabricated on silicon surfaces by dry etching and then copper nanoparticles were deposited on the micro-pin-fin surfaces by electrostatic deposition. Experimental results indicated that compared with a smooth surface, the micro pin fins increased the heat transfer coefficient and the critical heat flux by more than 200 and 65–83%, respectively, which were further enhanced by the nanoparticles up to 24% and more than 20%, respectively. Correspondingly, the enhancement mechanism was carefully explored by high-speed bubble visualizations, surface wickability measurements, and model analysis. It was quantitatively found that small bubble departure diameters with high bubble departure frequencies promoted high heat transfer coefficients. The wickability, which characterizes the ability of a liquid to rewet a surface, played an important role in determining the critical heat flux, but further analyses indicated that evaporation beneath bubbles was also essential and competition between the wicking and the evaporation finally triggered the critical heat flux.
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| 26. |
- Cao, Zhen, et al.
(författare)
-
Nucleate pool boiling heat transfer of acetone and HFE7200 on copper surfaces with nanoparticle coatings
- 2019
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 158, s. 5872-5879
-
Tidskriftsartikel (refereegranskat)abstract
- Nucleate pool boiling performance of two well-wetting liquids, i.e., acetone and HFE7200, on three nanoparticle-coatedsurfaces were experimentally studied and compared with that of the smoothsurface. Electrophoretic deposition was used to fabricate nano-porous surfaces.Surface roughness, static and advancing contact angles, capillarity of the smoothand coated surfaces were characterized. Compared to the smooth surface, thenanoparticle-coated surfaces decreased the wall superheat by more than 50% foracetone and 65% for HFE7200 at the same heat flux level, and accordinglyenhanced the heat transfer coefficient by up to 85% for acetone and up to 200%for HFE7200. Bubble departure diameters were measured and correlated with theadvancing contact angle, the capillary length and the Jacob number. A newmechanistic heat transfer model was proposed based on the heat flux partitionmethod. The advancing contact angle was suggested to be used for calculation ofthe active nucleation site density. Based on the mechanistic model, transientheat conduction on and around nucleation sites over the whole bubble cyclecontributes the most (>70%) to the total heat flux, while microlayerevaporation contributes around 10-30% to the total heat flux, with negligiblenatural convection. The critical heat flux was not enhanced for the twowell-wetting liquids.
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| 27. |
- Cao, Zhen, et al.
(författare)
-
Numerical study on heat transfer enhancement for laminar flow in a tube with mesh conical frustum inserts
- 2017
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Ingår i: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 72:1, s. 21-39
-
Tidskriftsartikel (refereegranskat)abstract
- Enhanced heat transfer tubes (EHTT) with segmented mesh-conical frustums are considered. Tube diameter and frustum apex angle are fixed as 20 mm and 60o, respectively. The height ratio of frustum and sliced part are set as a golden ratio (1.618). Laminar thermal-hydraulic performance and effects of some parameters, e.g., bottom frustum diameter and pitch, are numerically simulated. The equal equivalent diameter and total flow area criteria are adopted to simplify 3D mesh pores to 2D ones. Flow and temperature fields show large velocities and gradients close to the wall and smaller velocities in the bulk region. This enhances heat transfer with a limited pressure drop. EHTTs obtain 1.4 - 3.3 times higher heat transfer than bare tubes and the performance evaluation criterion (PEC) varies from 1.3 to 1.8. Nusselt number (Nu) and friction factor (f) correlations are proposed. New insights into heat transfer enhancement and tube configuration are provided.
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| 28. |
- Cao, Zhen, et al.
(författare)
-
Pool boiling heat transfer enhancement of water by gold nanoparticles with an electrophoretic deposition method
- 2019
-
Ingår i: Proceedings of the Asme International Mechanical Engineering Congress and Exposition, 2018, vol 8b. - : Amer Soc Mechanical Engineers. - 9780791852125
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Saturated pool boiling heat transfer of water is investigated experimentally on copper surfaces with nanoparticle coatings at atmospheric pressure. The coatings are generated by an electrophoretic deposition method (EPD). Three modified surfaces are prepared with gold nanoparticles of 0.20 mg, 0.25 mg and 0.30 mg, respectively. During the deposition, ethanol works as the solvent while the electrical potential and deposition time are controlled as 9.5 V and 30 min, respectively. The experimental results show that heat transfer coefficients (HTC) and critical heat fluxes (CHF) are enhanced on the modified surfaces. HTC increases with decreasing thickness of the coating, while CHF increases with increasing thickness of the coating. CHFs of EPD-0.20 mg, EPD-0.25 mg and EPD-0.30 mg are 93 W/cm2, 123 W/cm2 and 142 W/cm2, respectively, which are increased by 7%, 41% and 63% compared with the smooth surface. EPD-0.20 mg performs the best on heat transfer, with a maximum enhancement of around 60%. At the end, a brief review about mechanistic models of heat transfer at low and moderate heat fluxes is provided, based on which, the reasons why heat transfer is enhanced are discussed.
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| 29. |
- Cao, Zhen, et al.
(författare)
-
Pool boiling heat transfer of FC-72 on pin-fin silicon surfaces with nanoparticle deposition
- 2018
-
Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 126, s. 1019-1033
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, two types of micro-pin–fin configurations were fabricated on silicon surfaces by a dry etching method, i.e., staggered pin fins (#1) and aligned pin fins with empty areas (#2). The micro-pin–fin surfaces were then further modified by depositing FeMn oxide nanoparticles (∼35 nm) electrostatically for 8 h and 16 h, respectively, namely #1-8h, #1-16h, #2-8h and #2-16h. Subcooled pool boiling heat transfer was experimentally studied on these surfaces at atmospheric pressure, using FC-72 as the working fluid. The results showed that in comparison to the smooth surface, pool boiling heat transfer was significantly enhanced by the micro-pin-fin surfaces and the maximum superheat was considerably decreased. Additionally, critical heat fluxes were also greatly improved, e.g., the critical heat flux on #1 was almost twice of that on the smooth surface. Generally, the nanoparticle deposition could further enhance pool boiling heat transfer, including the heat transfer coefficient and critical heat flux (CHF). High speed visualizations were taken to explore the mechanisms behind the heat transfer performance. The bubble behavior on the micro-pin–fin surfaces with and without nanoparticles was compared at low, moderate and high heat fluxes, respectively. The wickability of FC-72 on the test surfaces was measured, based on which, a modified CHF model was proposed to predict the experimental CHFs. Accordingly, a possible mechanism of CHF enhancement was described.
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| 30. |
- Cao, Zhen, et al.
(författare)
-
Pool Boiling Heat Transfer of Water on Copper Surfaces With Nanoparticles Coating
- 2017
-
Ingår i: ASME 2017 International Mechanical Engineering Congress and Exposition. - 9780791858431 ; 8
-
Konferensbidrag (refereegranskat)abstract
- Saturated pool boiling heat transfer is investigated experimentally on a copper substrate with copper nanoparticle coatings at atmospheric pressure, in terms of critical heat flux (CHF) and heat transfer coefficient (HTC). Experiments are carried out on the substrate surface with a diameter of 12 mm using DI water as the working fluid. The coating is formed by stacking copper nanoparticles generated by an aerosol method. The aerosol nanoparticles are generated by a spark discharge generator with nitrogen gas as carrier gas and size-selected prior to electrostatic deposition. The thickness of the coating is quantified by the deposition time. In the present study, copper particles with diameter 35± 5 nm are selected, considering better coverage on the surface, while the deposition time is controlled as 4h and 8h, respectively.The boiling curves and heat transfer coefficient of MS-1 (4h deposition) and MS-2 (8h deposition) were compared with the BS (bare surface). The results show that CHFs of MS-1 and MS-2 are increased by 24% and 36%, respectively compared with the BS, while heat transfer is enhanced as well. High speed visualization tells that the coating provides more active nucleate sites and the hydrophobicity of the coating helps bubbles departure from the surface at low and moderate heat flux. At high heat flux, a hollow well occurs on MSs to supply liquid effectively to avoid dryout. Therefore, CHF and heat transfer are both improved.
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| 31. |
- Cao, Zhen, et al.
(författare)
-
Pool boiling of HFE-7200 on nanoparticle-coating surfaces: Experiments and heat transfer analysis
- 2018
-
Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310 .- 1879-2189. ; 133, s. 548-560
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, an electrophoretic deposition method was employed to modify copper surfaces withCu-Zn (100 nm) nanoparticles. Pool boiling heat transfer of HFE-7200 on the modified surfaces was experimentally studied. The results showed that the heat transfer coefficient on the modified surfaces was significantly enhanced compared with that on a smooth surface, e.g., a maximum 100% enhancement,while the maximum superheat on the modified surfaces was around 20 K lower than that on the smooth surface. However, the critical heat flux (CHF) was not improved considerably, and supplementary tests indicated that the wickability of HFE-7200 was almost the same on the modified surfaces and the smooth surface. The departure diameters of bubbles were recorded by a high speed camera, which were compared with several models in literature. Active nucleation site sizes were evaluated by the Hsu nucleation theory and active nucleation site densities were estimated by appropriate correlations.In addition, a heat transfer model, considering natural convection, re-formation of thermal boundary layer and microlayer evaporation, was formulated to predict the heat transfer on the modified surfaces and the smooth surface. A relatively good prediction was achieved.
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| 32. |
- Cao, Zhen, et al.
(författare)
-
Pool Boiling of NOVEC-649 on Microparticle-Coated and Nanoparticle-Coated Surfaces
- 2021
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 42:19-20, s. 1732-1747
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, microparticle coatings and nanoparticle coatings were fabricated on copper surfaces by an electrochemical deposition method and an electrophoretic deposition method, respectively. Pool boiling of NOVEC-649 was experimentally studied on the coated surfaces, concerning heat transfer, bubble dynamics, and critical heat fluxes. Compared with a smooth surface, heat transfer coefficients and critical heat flux (CHF) were improved, achieving a maximum heat transfer enhancement of 460% on the nanoparticle-coated surface and a maximum CHF enhancement of 60% on the microparticle-coated surface. Based on high speed visualizations, bubble departure diameters were measured and compared with several correlations, and then the heat transfer was analyzed by a mechanistic model, considering natural convection, transient heat conduction and microlayer evaporation. The mechanistic model demonstrated a good ability to predict the present results. In addition, wickability, representing a liquid supplement ability, was measured, indicating that the wickability enhancement was probably responsible for the CHF improvement.
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| 33. |
- Cao, Zhen
(författare)
-
Pool Boiling on Structured Surfaces: Heat Transfer and Critical Heat Flux : Experiments and Mechanistic Modelling
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, pool boiling heat transfer was experimentally studied on structured surfaces with dielectric liquids (HFE-7200, NOVEC-649, FC-72), organic liquids (Acetone, Pentane) and deionized water.In the first step, nanoparticle coatings on copper surfaces were prepared by an electrophoretic deposition method, with Cu-Zn nanoparticles (100 nm) and Cu nanoparticles (150 nm). Two types of nanoparticle-coating surfaces were prepared, namely nanoparticle coatings uniformly deposited on smooth surfaces and nanoparticle coatings partially deposited on smoothsurfaces. Pool boiling of HFE-7200 and acetone was tested on the coating surfaces. It is found that pool boiling heat transfer coefficients are significantly enhanced by nanoparticle coatings. However, the uniform coating cannot enhance the critical heat flux, while the partially-deposited coating can enhance critical heat flux. Mechanistic heat transfer models were developed to predict the heat transfer coefficients, considering natural convection, transient heat conduction, microlayer evaporation and micro convection, while the critical heat flux was analyzed from the point of wickability and hydrodynamic instability.In the following step, microporous coatings on copper surfaces were generated by an electrochemical deposition method, with electrolyte solutions (CuSO4+H2SO4). Pool boiling of HFE-7200, NOVEC-649 and water was tested. The results show that heat transfer coefficients and critical heat flux are enhanced, and the heat transfer coefficients are obviously dependent on deposition-relevant parameters, like deposition time and electrolyte concentration. Heat transfer coefficients were discussed mechanistically and empirically by a mechanistic model and correlations, while the critical heat flux was predicted by a modified force balance model which considers the forces exerted on vapor and assumes occurrence of the critical heat flux when the vapor expands on surfaces.Finally, hybrid micro/nano structures were fabricated on copper surfaces by femtosecond laser machining and electrophoretic deposition, and on silicon wafers by dry etching and electrostatic deposition. Pool boiling of acetone and FC-72 was investigated on the copper surfaces and the silicon wafers, respectively. It is found that the hybrid structures induce higher heat transfer coefficients than sole structures and wickability plays an important role on enhancement of the critical heat flux.
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| 34. |
- Cao, Zhen, et al.
(författare)
-
Water-oil flow in square microchannels with a crossed junction
- 2018
-
Ingår i: Fluid Machinery; Erosion, Slurry, Sedimentation; Experimental, Multiscale, and Numerical Methods for Multiphase Flows; Gas-Liquid, Gas-Solid, and Liquid-Solid Flows; Performance of Multiphase Flow Systems; Micro/Nano-Fluidics. - 9780791851579 ; 3
-
Konferensbidrag (refereegranskat)abstract
- In the present study, water-oil flow patterns and slug hydrodynamics were experimentally studied in square glass microchannels with various hydraulic diameters (Dh = 600 µm, 400 µm, 200 µm). The aqueous phase is the continuous phase while the organic phase is the dispersed phase. The ranges of flow rates of the continuous phase and the dispersed phase are 0-200 ml/h and 0-12 ml/h, 0-120 ml/h and 0-6 ml/h, and 0-60 ml/h and 0-2 ml/h in the microchannels with Dh = 600 µm, 400 µm and 200 µm, respectively. The results show that the hydraulic diameter has significant effects on flow patterns and three main flow patterns are observed, i.e., annular flow, slug flow and droplet flow. Generally, annular flow appeared at high flow rates of the dispersed phase and low flow rates of the continuous phase, while droplet flow appeared at low flow rates of the dispersed phase and high flow rates of the continuous phase. However, slug flow existed at comparable flow rates of the continuous and dispersed phases. A dimensionless analysis is carried out and a new dimensionless group including Weber number and Reynolds number is derived. The new defined dimensionless group performs well to develop a general flow pattern map. In addition, slug flow hydrodynamics are investigated as well in the present study, considering the slug length and slug velocity. Based on the present experimental results, a new scaling law is proposed to predict the slug length and it shows a good agreement with the experimental results. It has been widely reported that slug velocities depend linearly on the total flow rates of the two phases, which is consistent with the present study. The linear law provides a good prediction of the experimental slug velocities but different slopes are suggested in microchannels with different hydraulic diameters.
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| 35. |
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| 36. |
- Cheng, Shi-Ping, et al.
(författare)
-
Haplotype-resolved genome assembly and allele-specific gene expression in cultivated ginger
- 2021
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Ingår i: Horticulture Research. - : Springer Nature. - 2052-7276. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Ginger (Zingiber officinale) is one of the most valued spice plants worldwide; it is prized for its culinary and folk medicinal applications and is therefore of high economic and cultural importance. Here, we present a haplotype-resolved, chromosome-scale assembly for diploid ginger anchored to 11 pseudochromosome pairs with a total length of 3.1 Gb. Remarkable structural variation was identified between haplotypes, and two inversions larger than 15 Mb on chromosome 4 may be associated with ginger infertility. We performed a comprehensive, spatiotemporal, genome-wide analysis of allelic expression patterns, revealing that most alleles are coordinately expressed. The alleles that exhibited the largest differences in expression showed closer proximity to transposable elements, greater coding sequence divergence, more relaxed selection pressure, and more transcription factor binding site differences. We also predicted the transcription factors potentially regulating 6-gingerol biosynthesis. Our allele-aware assembly provides a powerful platform for future functional genomics, molecular breeding, and genome editing in ginger.
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| 37. |
- Du, Jianqiang, et al.
(författare)
-
Experimental study of pool boiling performance of Fe3O4 ferromagnetic nanofluid on a copper surface
- 2024
-
Ingår i: Applied Thermal Engineering. - 1359-4311. ; 248
-
Tidskriftsartikel (refereegranskat)abstract
- Nanofluids significantly enhance the critical heat flux of boiling heat transfer. This paper experimentally investigates the pool boiling performance and the influence mechanism of Fe3O4 nanofluids. Compared with deionized water, the 0.001 vol% nanofluid increases a maximum enhancement in critical heat flux by 47.90%. During nanofluid boiling, Fe3O4 nanoparticles are deposited on the surfaces. The nanoparticle deposition surfaces are physically characterized to explain the influence mechanism of Fe3O4 nanoparticles on boiling heat transfer. Nanoparticle deposition modifies the surface micro-morphology, which increases roughness and improves wettability. The changes are essential factors for the enhancement of the critical heat flux. This paper further analyses the boiling results of deionized water on the nanoparticle deposition surfaces. Compared with a polished surface, the critical heat flux and heat transfer coefficient of the nanoparticle deposition surface show maximum increases of 52.39% and 56.19%. Due to the similar enhancement of critical heat flux using the Fe3O4 nanofluid and the nanoparticle deposition surface, it is found that the increased critical heat flux of the nanofluids is attributed to the improvement of surface wettability and roughness by nanoparticle deposition. This study analyzes the mechanism of Fe3O4 nanofluid for enhancing pool boiling heat transfer from the perspective of modifying boiling surface characteristics by nanoparticle deposition, especially in wettability and roughness, which advances the understanding of enhanced boiling heat transfer by nanofluids.
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| 38. |
- Fu, Jiahong, et al.
(författare)
-
Effect of an impinging jet on the flow characteristics and thermal performance of mainstream in battery cooling of hybrid electric vehicles
- 2022
-
Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 183
-
Tidskriftsartikel (refereegranskat)abstract
- The novel concept of impinging jet cooling, i.e., an active-passive air cooling strategy, was proposed to achieve improved battery thermal management in hybrid vehicles, and this method is supported by excess high pressure discharged air. To comprehensively realize the active-passive combined cooling behavior, a rectangular channel with a jet impingement hole was utilized to experimentally and numerically study the flow characteristics and thermal performance of the joint cooling mechanism. The numerical results were confirmed by the experimental data in this work, the maximum deviations of the offset and Nusselt numbers are 18.8% and 7.5%, respectively. The thermal transport performs much better under the interaction between the mainstream and impinging jet, i.e., the average Nusselt number and maximum Nusselt number can be increased by 0.43-16.55, 5.73-34.42, respectively, at inlet pressures of the impinging jet in the range of 1–6 bar. The values of Nu/Nu0/(f/f0) 1/3 are improved by 1.52–3.33. The jet fluid was deflected under the influence of the mainstream and a vortex can be induced, which is beneficial for the heat transfer performance. The jet fluid closely reached the heated plane at a relatively large volume flow rate and the heat transfer performance was excellent once the jet fluid touched the heated plane. The thermal boundary layer becomes thinned under the impact of the impinging jet but the magnitude of the reduction is relatively slight.
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| 39. |
- Fu, Jiahong, et al.
(författare)
-
EXPERIMENTAL STUDY ON HEAT TRANSFER ENHANCEMENT OF AIR JET IMPINGEMENT FOR ELECTRONICS THERMAL MANAGEMENT
- 2022
-
Ingår i: Journal of Enhanced Heat Transfer. - 1065-5131. ; 29:4, s. 63-80
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Tidskriftsartikel (refereegranskat)abstract
- Jet impingement cooling was investigated on a flat heating surface placed in a flow channel, including single jet cooling, in-line double jet cooling, and combined crossflow and jet cooling; cross-flow cooling was a baseline for comparison. In addition, the in-line double jet cooling was explored with various jet distances. Local Nusselt number distribution was experimentally achieved by the liquid crystal method, and the measurements were carried out under various jet pressures ranging from 1 bar to 4 bar. It was found that heat transfer depends on the jet distance because one jet may produce a crossflow effect on the other jet, affecting the formation of longitudinal vortices which could enhance heat transfer. It was seen that in comparison to the crossflow cooling, the average Nusselt number is enhanced by 110%, 150%, and 380%by the single jet cooling, the in-line double jet cooling, and the combined cooling, respectively, and correspondingly the maximum Nusselt number is enhanced by 160%, 240%, and 540%, respectively. In the combined cooling, there is a deflection distance ranging from 0 mm to 10 mm depending on the jet pressure.
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| 40. |
- Han, Hedong, et al.
(författare)
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Prevalence, trends, and outcomes of atrial fibrillation in hospitalized patients with metastatic cancer : findings from a national sample
- 2021
-
Ingår i: Cancer Medicine. - : John Wiley & Sons. - 2045-7634. ; 10:16, s. 5661-5670
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Epidemiological evidence regarding the link between cancer and atrial fibrillation (AF) are limited and outcomes of metastatic cancer comorbid with AF need to be elucidated.Objective: This study aims to evaluate the prevalence, temporal trends, and outcomes of AF in hospitalized metastatic cancer patients.Methods: The National Inpatient Sample (NIS) database was used to identify adult patients with metastatic tumors from 2003 to 2014. We analyzed the trends in AF prevalence, in-hospital mortality, total cost, length of stay (LOS), and comorbidities pertaining to metastatic cancer. Multivariable-adjusted models were used to evaluate the association of AF with clinical factors, in-hospital mortality, total cost, and LOS.Results: Among 2,478,598 patients with metastatic cancer, 8.74% (216,737) were diagnosed with AF. The proportion of comorbid AF increased from 8.28% in 2003 to 10.06% in 2014 (p < 0.0001). Older age, white race, male, Medicare, higher income, larger hospital bed size, and urban teaching hospital were associated with higher AF occurrence. Among primary tumor sites, lung cancer experienced the highest odds of AF compared to other cancers. Patients with metastasis to lymph node and respiratory organ had higher odds of AF. In metastatic cancer, AF was associated with higher in-hospital mortality (odds ratio: 1.48; 95% confidence interval: 1.43-1.54), 18% longer LOS, and 19% higher cost.Conclusions: AF prevalence in metastatic cancer continues to increase from 2003 to 2014. AF is linked to poorer prognosis and higher healthcare resource utilization. As the population ages, optimal preventive and treatment management strategies are needed for metastatic cancer comorbid with AF.
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| 41. |
- Jiang, Haiying, et al.
(författare)
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A Highly Crystalline Wide-Band-Gap Conjugated Polymer toward High-Performance As-Cast Nonfullerene Polymer Solar Cells
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 9:41, s. 36061-36069
-
Tidskriftsartikel (refereegranskat)abstract
- A new wide-band-gap conjugated polymer PBODT was successfully synthesized that showed high crystallinity and was utilized as, the active material in nonfullerene bulk-heterojunction, polymer solar cells (PSCs). The photovoltaic devices based on the as-cast blend films of PBODT with ITIC and IDIC acceptors showed notable power conversion efficiencies (PCEs) of 7.06% and 9:09%, with high open-circuit voltages of 1.00 and 0.93 V that correspond to low energy losses of 0.59 and 0.69 eV, respectively. In the case of PBODT:ITIC, lower exciton quenching efficiency and monomolecular recombination are found for devices with small driving force. On the other hand, the relatively higher driving force and suppressed monomolecular recombination for PBODT:IDIC devices are identified to be the reason for their higher short-circuit current density (J(sc)) and higher PCEs. In addition, when processed with the nonchlorinated solvent 1,2,4-trimethylbenzene, a good, PCE of 8.19% was still, achieved for the IDIC-based device. Our work shows that such wide-band-gap polymers have great potential for the environmentally friendly fabrication of highly efficient PSCs.
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| 42. |
- Lensink, Marc F., et al.
(författare)
-
Impact of AlphaFold on structure prediction of protein complexes: The CASP15-CAPRI experiment
- 2023
-
Ingår i: Proteins. - : WILEY. - 0887-3585 .- 1097-0134.
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results for CAPRI Round 54, the 5th joint CASP-CAPRI protein assembly prediction challenge. The Round offered 37 targets, including 14 homodimers, 3 homo-trimers, 13 heterodimers including 3 antibody-antigen complexes, and 7 large assemblies. On average similar to 70 CASP and CAPRI predictor groups, including more than 20 automatics servers, submitted models for each target. A total of 21 941 models submitted by these groups and by 15 CAPRI scorer groups were evaluated using the CAPRI model quality measures and the DockQ score consolidating these measures. The prediction performance was quantified by a weighted score based on the number of models of acceptable quality or higher submitted by each group among their five best models. Results show substantial progress achieved across a significant fraction of the 60+ participating groups. High-quality models were produced for about 40% of the targets compared to 8% two years earlier. This remarkable improvement is due to the wide use of the AlphaFold2 and AlphaFold2-Multimer software and the confidence metrics they provide. Notably, expanded sampling of candidate solutions by manipulating these deep learning inference engines, enriching multiple sequence alignments, or integration of advanced modeling tools, enabled top performing groups to exceed the performance of a standard AlphaFold2-Multimer version used as a yard stick. This notwithstanding, performance remained poor for complexes with antibodies and nanobodies, where evolutionary relationships between the binding partners are lacking, and for complexes featuring conformational flexibility, clearly indicating that the prediction of protein complexes remains a challenging problem.
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| 43. |
- Li, Kaihui, et al.
(författare)
-
Three‐dimensional discrete element simulation of indirect tensile behaviour of a transversely isotropic rock
- 2020
-
Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : John Wiley & Sons. - 0363-9061 .- 1096-9853. ; 44:13, s. 1812-1832
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the development of a three‐dimensional discrete element model using flat‐joint and smooth‐joint contact models to investigate the effect of anisotropy on the tensile behaviour of slate, a transversely isotropic rock, under Brazilian testing from both macro and microscales. The effect of anisotropy is further realised by exploring the influence of foliation orientations (β and ψ ) on the tensile strength, fracture pattern, microcracking and stress distribution of the transversely isotropic rock. The variation of tensile strength with foliation orientation is presented. The cross‐weak‐plane fracture growth observed in laboratory is reproduced, and the criterion for which to form is also given from the aspect of foliation orientation. Furthermore, the proportional variations of microcracks well account for the effects of foliation orientation on the tensile strength and failure pattern. Finally, it is found that the existence of weak planes increases both the heterogeneity and the anisotropy of stress distributions within the transversely isotropic rock, with the degree of influence varying with the foliation orientation.
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| 44. |
- Li, Yong, et al.
(författare)
-
Buoyancy and Thermal Acceleration of Supercritical n-Decane in a Rectangular Channel
- 2022
-
Ingår i: Journal of Thermophysics and Heat Transfer. - 0887-8722. ; 36:2, s. 419-430
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, supercritical n-decane flowing in ducts with different orientations is thoroughly investigated in terms of secondary flow, wall shear stress, and thermal acceleration. It is known that the secondary flow strength hardly plays a role in cases of flowing upward, flowing downward, or flowing horizontally at a small heat flux/mass flux. Still, an attachment point can be found at the center for cases of flowing upward and flowing downward, and this enhances the heat transfer. For a large heat flux/mass flux, thermal transport depends not only on the secondary flow strength but also on the secondary flow structure. Besides, a separation point is found at the center for flowing up/downward cases, and the more adjacent the attachment point is to the heated wall, the more serious is the thermal transport. The wall shear stress is beneficial to heat transfer but also relies on the distribution profile. Thermal acceleration can really diminish or even restrain the HTD phenomenon, but it is not the reason to cause the difference of heat transfer behavior for channels with different orientations.
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| 45. |
- Li, Yong, et al.
(författare)
-
竖直矩形通道内超临界正癸烷振荡特性的大涡模拟
- 2022
-
Ingår i: Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics. - 1005-2615. ; 54:2, s. 281-289
-
Tidskriftsartikel (refereegranskat)abstract
- Active generative cooling based on supercritical hydrocarbon fuel is regarded as one of the most promising methods for scramjet thermal management. A large eddy simulation method is used to explore the transient change law of the initial flow, and heat transfer behaviors of supercritical hydrocarbon fuel is in rectangular channels. An oscillation effect can be proved in the convective heat transfer process, i.e., the temperature and velocity distributions fluctuate strongly. By monitoring the velocity variation rule of 10-4 s time scale, the approximate trigonometric frequency and amplitude are present in this oscillation. At the initial heating condition, the high-temperature fluid, which is close to the heated wall, flows into the low-temperature region under the effect of buoyancy force. As the fluid temperature gradually reaches the pseudo-critical value, its thermo-physical properties change dramatically. The friction factor oscillates as well as the fluid kinetic energy. Correspondingly, the enhanced vortex is induced away from the heated wall. Over time, the enhanced vortex begins to move to the heated wall and the low-temperature fluid impinges on the wall. Consequently, the thermal transport is enhanced.
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| 46. |
- Lin, Zhen, et al.
(författare)
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Discharge Against Medical Advice in Acute Ischemic Stroke : the Risk of 30-Day Unplanned Readmission
- 2021
-
Ingår i: Journal of general internal medicine. - : Springer. - 0884-8734 .- 1525-1497. ; 36:5, s. 1206-1213
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Discharge against medical advice may be associated with more readmissions.OBJECTIVE: To evaluate DAMA in patients with acute ischemic stroke (AIS) and identify the relationship between DAMA and 30-day unplanned readmissions.DESIGN: A retrospective cohort study.PARTICIPANTS: The National Readmission Database was used to identify inpatients with a primary diagnosis of AIS who were either discharged home or DAMA between 2010 and 2017 in the USA.MEASURES: Demographic features, hospital type, comorbidities, stroke risk factors, severity indices, and treatments were compared between patients discharged routinely and DAMA. Multivariable logistic regression was used to evaluate predictors of DAMA, and a double robust inverse probability of treatment weighting method was used to assess the association between DAMA and 30-day unplanned readmissions.KEY RESULTS: Overall, 1,335,484 patients with AIS were included, of whom 2.09% (n = 27,892) were DAMA. The prevalence of DAMA in AIS patients increased from 1.65 in 2010 to 2.57% in 2017. The rates of 30-day unplanned readmissions for DAMA and non-DAMA patients were 16.81% and 7.78%, respectively. Patients with drug abuse, alcohol abuse, smoking, prior stroke, psychoses, and intravenous thrombolysis had greater odds of DAMA. DAMA was associated with all-cause readmissions (OR, 2.04; 95% CI, 2.01-2.07) and remained a strong predictor for transient ischemic attack/stroke-specific and cardiac-specific causes of readmissions.CONCLUSIONS: Although the DAMA rate is low in AIS patients, DAMA is a risk factor for all-cause and recurrent stroke-specific readmissions. Future studies are needed to address issues around compliance and engagement with health care to reduce DAMA.
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| 47. |
- Lin, Zhen, et al.
(författare)
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Outcomes after readmission at the index or nonindex hospital following acute myocardial infarction complicated by cardiogenic shock
- 2021
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Ingår i: Clinical Cardiology. - : John Wiley & Sons. - 0160-9289 .- 1932-8737. ; 44:2, s. 200-209
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the prevalence and outcomes of readmission to nonindex hospitals after an admission for acute myocardial infarction complicated by cardiogenic shock (AMI-CS). We aimed to determine the rate of nonindex readmissions following AMI-CS and to evaluate its association with clinical factors, hospitalization cost, length of stay (LOS), and in-hospital mortality rates.HYPOTHESIS: Nonindex readmission may lead to worse in-hospital outcomes.METHODS: We reviewed the data of inpatients with AMI-CS between 2010 and 2017 using the National Readmission Database. The survey analytical methods recommended by the Healthcare Cost and Utilization Project were used for national estimates. Multiple regression models were used to evaluate the predictors of nonindex readmission, and its association with hospitalization cost, LOS, and in-hospital mortality rates.RESULTS: Of 238 349 patients with AMI-CS, 28028 (11.76%) had an unplanned readmission within 30 days. Of these patients, 7423 (26.48%) were readmitted to nonindex hospitals. Compared with index readmission, nonindex readmission was associated with higher hospitalization costs (p < .0001), longer LOS (p < .0001), and increased in-hospital mortality rates (p = .0016). Patients who had a history of percutaneous coronary intervention, received intubation/mechanical ventilation, or left against medical advice during the initial admission had greater odds of a nonindex readmission.CONCLUSIONS: Over one-fourth of readmissions following AMI-CS were to nonindex hospitals. These admissions were associated with higher hospitalization costs, longer LOS, and higher in-hospital mortality rates. Further studies are needed to evaluate whether a continuity of care plan in the acute hospital setting can improve outcomes after AMI-CS.
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| 48. |
- Lin, Zhen, et al.
(författare)
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Worse Outcomes After Readmission to a Different Hospital After Sepsis : A Nationwide Cohort Study
- 2022
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Ingår i: Journal of Emergency Medicine. - : Elsevier. - 0736-4679 .- 1090-1280. ; 63:4, s. 569-581
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In the United States, sepsis accounts for 13% of the total hospital expenses and > 50% of hospital deaths. Moreover, people with sepsis are more likely to be readmitted.OBJECTIVE: The aim of this study was to assess the prevalence and outcomes of different hospital readmissions (DHRs) in patients with sepsis, and the factors associated with DHR.METHODS: We used data from the Nationwide Readmissions Database of the United States in 2017 to identify patients admitted for sepsis. Multivariable logistic regression analysis was used to evaluate the factors associated with DHR; five models were constructed to elucidate the relationship between DHR and in-hospital outcomes.RESULTS: In 2017, 85,120 (21.97%) of all patients with sepsis readmitted within 30 days in the United States were readmitted to a different hospital. The most common reason for readmission was infection irrespective of hospital status. Compared with the patients with sepsis who were readmitted to the same hospital, DHR was associated with higher hospitalization costs ($2264; 95% CI $1755-$2772; p < 0.001), longer length of stay (0.58 days; 95% CI 0.44-0.71 days; p < 0.001), and higher risk of in-hospital mortality (odds ratio 1.63; 95% CI 1.55-1.72; p < 0.001).CONCLUSIONS: DHR occurred in one-fifth of patients with sepsis in the United States. Our findings suggest that patients readmitted to a different hospital within 30 days may experience higher in-hospital mortality, longer length of stay, and higher hospitalization costs. Future studies need to examine whether continuity of care can improve the prognosis of patients with sepsis.
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| 49. |
- Liu, Bin, et al.
(författare)
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Pool boiling heat transfer of N-pentane on micro/nanostructured surfaces
- 2018
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Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 130, s. 386-394
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, one type of uniformly nanostructured surface (NPDS) was modified by electrophoretic deposition. Two kinds of micro/nanostructured surfaces (FLS1 and FLS2) were fabricated on copper surfaces by femtosecond laser processing. The micro/nanostructured surfaces were further modified by electrophoretic deposition. Afterwards, composite micro/nanostructured surfaces (CS1 and CS2) were developed. Saturated pool boiling heat transfer of the modified surfaces was investigated experimentally. An organic fluid, n-pentane was chosen as the working liquid. Heat transfer coefficient and critical heat flux (CHF) of smooth and micro/nanostructured surfaces were studied. The results showed that the heat transfer coefficient (HTC) of all structured surfaces increased obviously with a notable decrease of wall superheat at CHF compared to the smooth surface, which was attributed to increments in nucleation site density and heat transfer area. The CHF of femtosecond laser processed surfaces was also increased compared with the smooth surface due to a much higher liquid spreading ability, while a uniformly nanostructured surface has no augmentation in CHF. Composite micro/nanostructured surfaces show the best heat transfer performance among all tested surfaces, and the critical heat flux and heat transfer coefficient were increased by more than 60% and 300% over the smooth surface, respectively. The liquid spreading ability of n-pentane on the tested surfaces was measured. For the well wetting liquid, the liquid spreading ability of the heated surface, instead of the wettability, is the main factor for CHF enhancement. It is suggested that a surface with multiscale structures can be an efficient way for boiling heat transfer enhancement.
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| 50. |
- Liu, Zhan, et al.
(författare)
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An ultralow-temperature cascade refrigeration unit with natural refrigerant pair R290-R170 : Performance evaluation under different ambient and freezing temperatures
- 2023
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Ingår i: Thermal Science and Engineering Progress. - 2451-9049. ; 46
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Tidskriftsartikel (refereegranskat)abstract
- The global demand for ultralow-temperature (ULT) refrigeration units gets greatly promoted, for storage, transportation, and distribution of COVID-19 vaccines. In this work, a ULT freezer is developed with a cascade refrigeration system (CRS) utilizing environmentally friendly refrigerants R290 and R170. The performance of the ULT freezer is experimentally evaluated under different ambient temperatures Tamb and freezing temperatures Tfreezing. The result shows that once the refrigeration system starts, the freezer enters a pull-down period and then reaches stable or periodic on-off operation. The monitored temperatures present drastic variations in the low-temperature cycle (LTC) and show a relatively stable start-up process in the high-temperature cycle (HTC). The monitored temperature rises when Tamb increases from 16 °C to 32 °C. The increasing Tamb brings about a larger temperature drop crossing the pre-cooled condenser, cascade heat exchanger, and high-temperature condenser, and a smaller temperature reduction through the anti-condensation. As Tfreezing decreases from −60 °C to −86 °C, the suction/discharge gas temperatures increase in the low-temperature compressor, while the other monitored temperatures reduce. The largest temperature non-uniformity in the freezer is 9.19 °C, and the lowest wall temperature can reach −90.52 °C. With Tamb ranging from 16 °C to 32 °C, the power consumption of the freezer increases from 896 W to 912 W. When Tfreezing varies from −60 °C to −86 °C, the CRS's consumed power reduces from 804 W to 904 W. The present freezer can easily obtain low temperatures e.g., −81 °C, and reach a lower temperature, such as −86 °C with proper improvements to reduce cold loss.
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