| 1. |
- Ma, Zhaoying, et al.
(författare)
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Mineralogical and magnetic variations of periglacial loess in SE Tibet reveal mid-Pleistocene expansion of Tibetan glacial activity
- 2024
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 330
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Tidskriftsartikel (refereegranskat)abstract
- The formation and evolution of the cryosphere on the Tibetan Plateau is of great significance in understanding the Earth's carbon and climatic system. Periglacial loess deposits in southeastern Tibet offer a means to constrain this history as they contain critical information on glacial grinding and frost shattering processes in high-altitude mountain regions through time, which yield lithogenic fractions of largely loess silts and sands. Based on combined analyses of lithogenic magnetic properties and mineralogical composition, here we find that increasing high mountain production and supply of fresh detrital components since the mid-Pleistocene climate transition (MPT, 1.2–0.7 Ma) led to a substantial increase of the lithogenic susceptibility and decrease in chemical weathering intensity of periglacial loess in southeastern Tibet. The agreement of these findings with similar results from eolian loess on the northern margins of the Tibetan Plateau suggests a plateau-wide glacier expansion during the MPT. Enhanced glacial erosion and freeze-thaw activities occurred in the high-altitude mountain regions of the plateau during the MPT, thereby providing vast amounts of fresh detritus for the formation of loess deposits. High and constant values of lithogenic magnetic parameters in the loess deposits after 0.7–0.6 Ma further indicate that the Middle Pleistocene is a critical period for the establishment of modern-like glacial and periglacial landforms on the Tibetan Plateau. Our results further suggest that enhanced Quaternary glaciation in SE Tibet occurred earlier than in the north, which we attribute to climate cooling combined with regional seasonal snowline lowering. As such, a close relationship exists between global climate changes, development of pan-Tibetan glaciations, and large-scale dust emission.
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| 2. |
- 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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| 3. |
- Cao, Zhen, et al.
(författare)
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Pool boiling heat transfer of FC-72 on pin-fin silicon surfaces with nanoparticle deposition
- 2018
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 126, s. 1019-1033
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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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| 4. |
- Conti, David, V, et al.
(författare)
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Trans-ancestry genome-wide association meta-analysis of prostate cancer identifies new susceptibility loci and informs genetic risk prediction
- 2021
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Ingår i: Nature Genetics. - : Springer Nature. - 1061-4036 .- 1546-1718. ; 53:1, s. 65-75
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Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is a highly heritable disease with large disparities in incidence rates across ancestry populations. We conducted a multiancestry meta-analysis of prostate cancer genome-wide association studies (107,247 cases and 127,006 controls) and identified 86 new genetic risk variants independently associated with prostate cancer risk, bringing the total to 269 known risk variants. The top genetic risk score (GRS) decile was associated with odds ratios that ranged from 5.06 (95% confidence interval (CI), 4.84-5.29) for men of European ancestry to 3.74 (95% CI, 3.36-4.17) for men of African ancestry. Men of African ancestry were estimated to have a mean GRS that was 2.18-times higher (95% CI, 2.14-2.22), and men of East Asian ancestry 0.73-times lower (95% CI, 0.71-0.76), than men of European ancestry. These findings support the role of germline variation contributing to population differences in prostate cancer risk, with the GRS offering an approach for personalized risk prediction. A meta-analysis of genome-wide association studies across different populations highlights new risk loci and provides a genetic risk score that can stratify prostate cancer risk across ancestries.
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| 5. |
- He, Li, et al.
(författare)
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In silico promoter analysis and functional validation identify CmZFH, the co-regulator of hypoxia-responsive genes CmScylla and CmLPCAT
- 2022
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Ingår i: Insect Biochemistry and Molecular Biology. - : Elsevier. - 0965-1748 .- 1879-0240. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen (O2) plays an essential role in aerobic organisms including terrestrial insects. Under hypoxic stress, the cowpea bruchid (Callosobruchus maculatus) ceases feeding and growth. However, larvae, particularly 4th instar larvae exhibit very high tolerance to hypoxia and can recover normal growth once brought to normoxia. To better understand the molecular mechanism that enables insects to cope with low O2 stress, we performed RNA-seq to distinguish hypoxia-responsive genes in midguts and subsequently identified potential common cis-elements in promoters of hypoxia-induced and -repressed genes, respectively. Selected elements were subjected to gel-shift and transient transfection assays to confirm their cis-regulatory function. Of these putative common cis-elements, AREB6 appeared to regulate the expression of CmLPCAT and CmScylla, two hypoxia-induced genes. CmZFH, the putative AREB6-binding protein, was hypoxia-inducible. Transient expression of CmZFH in Drosophila S2 cells activated CmLPCAT and CmScylla, and their induction was likely through interaction of CmZFH with AREB6. Binding to AREB6 was further confirmed by bacterially expressed CmZFH recombinant protein. Deletion analyses indicated that the N-terminal zinc-finger cluster of CmZFH was the key AREB6-binding domain. Through in silico and experimental exploration, we discovered novel transcriptional regulatory components associated with gene expression dynamics under hypoxia that facilitated insect survival.
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| 6. |
- Leng, Xue-Li, et al.
(författare)
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Spiral Coil Inserts for Heat Transfer Enhancement in a Parallel-plate Channel
- 2014
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Ingår i: Numerical Heat Transfer Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 66:7, s. 756-772
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Tidskriftsartikel (refereegranskat)abstract
- The flow fields and heat transfer characteristics in a parallel-plate channel with a transversely placed spiral coil insert were investigated by three-dimensional numerical simulation. The structure of multi-longitudinal-vortices (MLVs) induced by the spiral coil and the effects of MLVs on velocity and temperature fields were studied. The three-dimensional spiral coil induces a series of longitudinal vortices in the channel including leading longitudinal vortex, mainstream longitudinal vortices, near-wall longitudinal vortices, and rear central longitudinal vortex. Transport by the longitudinal vortices can increase the mass exchange between the boundary layer and the mainstream, which speeds up the heat migration from the channel walls and enhances the heat diffusion in the mainstream.
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| 7. |
- Liang, Miaomiao, et al.
(författare)
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Phytochemicals with activity against methicillin-resistant Staphylococcus aureus
- 2022
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Ingår i: Phytomedicine. - : Elsevier. - 0944-7113 .- 1618-095X. ; 100
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Forskningsöversikt (refereegranskat)abstract
- Background: The evolution of resistance to antimicrobials is a ubiquitous phenomenon. The evolution of antibiotic resistance in Staphylococcus aureus suggests that there is no remedy with sustaining effectiveness against this pathogen. The limited number of antibacterial drug classes and the common occurrence of cross-resistant bacteria reinforce the urgent need to discover new compounds targeting novel cellular functions. Natural products are a potential source of novel antibacterial agents. Anti-MRSA (methicillin-resistant S. aureus) bioactive compounds from Streptomyces and the anti-MRSA activity of a series of plant extracts have been reviewed respectively. However, there has been no detailed review of the precise bioactive components from plants.Purpose: The present review aimed to summarize the phytochemicals that have been reported with anti-MRSA activities, analyze their structure-activity relationship and novel anti-MRSA mechanisms.Methods: Data contained in this review article are compiled from the authoritative databases PubMed, Web of Science, Google Scholar, and so on.Results: This review summarizes 100 phytochemicals (27 flavonoids, 23 alkaloids, 17 terpenes and 33 others) that have been tested for their anti-MRSA activity. Among these phytochemicals, 39 compounds showed remarkable anti-MRSA activity with MIC values less than 10 mu g/ml, 14 compounds with MIC ranges including values <10 mu g/ml, 5 compounds with MIC values less than 5 mu M; 11 phytochemicals show synergism anti-MRSA effects in combination with antibiotics. Phytochemicals exerted anti-MRSA activities mainly by destroying the membrane structure and inhibiting the efflux pump.Conclusions: The 58 compounds with excellent anti-MRSA activity the 11 compounds with synergistic anti-MRSA effect, especially cannabinoids, xanthones and fatty acids should be further studied in vitro. Novel targets, such as cell membrane and efflux pump could be promising alternatives to develop antibacterial drugs in the future in order to prevent drug resistance.
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| 8. |
- 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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| 9. |
- Qian, Jy, et al.
(författare)
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Heat transfer analysis on dimple geometries and arrangements in dimple jacketed heat exchanger
- 2019
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Ingår i: International Journal of Numerical Methods for Heat and Fluid Flow. - 0961-5539. ; 29:8, s. 2775-2791
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this paper is to study the effects of dimple geometries and arrangements on the heat transfer enhancement in a dimple jacketed heat exchanger. Design/methodology/approach: For the purpose of this paper, with the experimental validated numerical model, this paper carries out numerical simulations of both single dimples with different geometries and the whole dimple jacketed heat exchanger with different dimple arrangements. For a single dimple, its secondary vortex flow, temperature differences and the pressure drop performance for different geometries are analyzed. For the whole dimple jacketed heat exchanger, the heat transfer and pressure drop performances are investigated by comparing the no dimple, triangular and rectangular dimple arrangements. Findings: Results show that dimples can improve the heat transfer efficiency compared with conventional jacketed heat exchanger, and specific geometries and arrangement of dimples for better heat transfer performance are figured out. Originality/value: This paper considers both dimple geometries and arrangements, which can be useful for further applications in specific integrated devices or similar applications.
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| 10. |
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